Patent Publication Number: US-2023143307-A1

Title: Substrate processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional of and claims the benefit of U.S. provisional patent application No. 63/273,579 filed on Oct. 29, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The exemplary embodiment generally relates to substrate processing equipment, and more particularly, to substrate transports of the substrate processing equipment. 
     2. Brief Description of Related Developments 
     Semiconductor automation generally comprises a series of building blocks that are required to support the implementation of processes to ultimately achieve predetermined levels of quality and reproducibility in semiconductor chip manufacturing. One component of semiconductor automation is the wafer (also referred to as a substrate) handler that transports the wafer or substrate between load locks and process modules and/or between process modules (e.g., in the case of sequential process tool architectures). 
     Conventional wafer handlers employed in semiconductor automation generally comprise multi-link robotic manipulators. The multi-link robotic manipulators have end effectors that hold and transport wafers or substrates from one location to another location. To determine the position of an end effector in space, a set of position feedback sensors is employed. The set of position feedback sensors is generally mounted, at least in part, to shafts of actuators that drive the links of the multi-ling robotic manipulator. Robotic kinematic errors, such as mechanical hysteresis, vibration, and thermal expansion can significantly contribute to accuracy errors with respect to the actual location of the end effector in space. 
     As an alternative to the wafer handlers noted above, magnetically levitated wafer conveyors may be employed where an alternating current magnetic floating apparatus for floating and conveying a conductive floating body or paramagnetic or nonmagnetic metallic material above a line of alternating current electromagnets is provided. The position of these magnetically levitated wafer conveyors is determined by using a network of distributed sensors collocated within the tool the magnetically levitated wafer conveyor operates. This network of distributed sensors and the respective wiring harnesses compete with the electromagnets for space within the tool increasing at least the footprint of the tool. These sensors are also, at least partially, located within a sealed environment in which the floating body moves, which may result in specially machined features being employed in the tool to facilitate placement of the sensors at least partially within the sealed environment or otherwise enable the network of sensors to be integrated with the tool. It is further noted that the network of sensors dedicated to position feedback of the floating body has a cost associated therewith that serves to increase the overall cost of the tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of the disclosed embodiment are explained in the following description, taken in connection with the accompanying drawings, wherein: 
         FIG.  1 A  is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  1 B  is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  2    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  3    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  4    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  5    is a schematic plan view of a substrate processing system incorporating aspects of the disclosed embodiment; 
         FIG.  6    is an exemplary substrate handler motion of the substrate processing apparatus described herein in accordance with aspects of the disclosed embodiment; 
         FIG.  7    is a schematic plan view of a substrate processing system incorporating aspects of the disclosed embodiment; 
         FIG.  8    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  8 A  is a schematic perspective view of a portion of a substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  9    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  10    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  10 A  is a schematic perspective view of a portion of a substrate handler of  FIG.  10    in accordance with aspects of the disclosed embodiment; 
         FIG.  11    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  11 A  is a schematic perspective view of a portion of a substrate handler of  FIG.  11    in accordance with aspects of the disclosed embodiment; 
         FIG.  12 A  is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  12 B  is a schematic elevation view of the substrate processing apparatus of  FIG.  12 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  13 A  is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  13 B  is a schematic elevation view of the substrate processing apparatus of  FIG.  13 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  14    is a schematic plan view of a substrate processing apparatus incorporating aspects of the disclosed embodiment; 
         FIG.  14 A  is a schematic plan view of a portion of the substrate processing apparatus of  FIG.  14    in accordance with aspects of the disclosed embodiment; 
         FIG.  14 B  is a schematic elevation view of a substrate transport cart in accordance with aspects of the disclosed embodiment; 
         FIG.  14 C  is a schematic plan view of the substrate transport cart in  FIG.  14 B  in accordance with aspects of the disclosed embodiment; 
         FIG.  15 A  is a front elevation view of a substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  15 B  is a schematic side elevation view of the substrate handler of  FIG.  15 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  15 C  is a schematic plan view of the substrate handler of  FIG.  15 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  16 A  is a schematic plan view of the substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  16 B  is a schematic side elevation view of the substrate handler of  FIG.  16 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  16 C  is a schematic plan view of a portion of a substrate processing apparatus including the substrate handler of  FIG.  16 A  in accordance with aspects of the disclosed embodiment; 
         FIG.  17    is a schematic illustration of an exemplary actuator control system network in accordance with aspects of the disclosed embodiment; 
         FIG.  18    is a schematic perspective illustration of a portion of a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  19    is an exemplary schematic electric circuit diagram of an electromagnet of a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  20    is an exemplary schematic diagram of a driver circuit for electromagnets of a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  21 A  is a schematic illustration of a response of an electromagnet to presence of a wafer handler in a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  21 B  is a schematic illustration of a response of an electromagnet to presence of a wafer handler in a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  21 C  is an exemplary graph illustrating electromagnet/wafer handler base inductance versus position of the wafer handler base in accordance with aspects of the disclosed embodiment; 
         FIG.  22    is a schematic illustration of an electromagnet control system and electromagnet array of a substrate processing apparatus in accordance with aspects of the disclosed embodiment; 
         FIG.  23    is a schematic illustration of power factor patterns/matrices, of the electromagnet array of  FIG.  22   , corresponding to respective wafer handlers in accordance with aspects of the disclosed embodiment; 
         FIG.  24    is an exemplary illustration of a transformation of electromagnet measurements, of the electromagnet array of  FIG.  22   , to spatial position of a wafer handler in accordance with aspects of the disclosed embodiment; 
         FIG.  25    is a schematic illustration of a multi-frequency alternating current and alternating current voltage for electromagnets in an array of electromagnets for effecting position determination, levitation, and propulsion of a wafer handler in accordance with aspects of the disclosed embodiment; 
         FIGS.  26  and  27    respectively illustrate a base of a wafer handler positioned adjacent an array of electromagnets and a power factor variation of the array of electromagnets based on position of the base in accordance with aspects of the disclosed embodiment; 
         FIG.  28    is an exemplary block diagram of an induction based position determination in accordance with aspects of the disclosed embodiment; 
         FIG.  29 A  is a schematic illustration of an exemplary motion control of a substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  29 B  is a schematic perspective illustration of a substrate handler motion in accordance with aspects of the disclosed embodiment; 
         FIG.  30    is a free body force diagram with respect to a maximum allowed acceleration with conventional substrate transport apparatus; 
         FIG.  31    is a free body force diagram illustrating an effect of pitch angle on acceleration of a substrate handler with respect to substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  32 A  is a free body force diagram of a substrate illustrating the effects of pitch angle, without friction, on substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  32 B  is an exemplary graph illustrating propulsion acceleration in relation to pitch angle, without friction, with respect to substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  33 A  is a free body force diagram of a substrate illustrating the effects of pitch angle, with friction, on substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  33 B  is a free body force diagram of a substrate illustrating the effects of pitch angle, with friction, on substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  34    is an exemplary graph illustrating acceleration limits in relation to pitch angle, with friction, with respect to substrate slippage in accordance with aspects of the disclosed embodiment; 
         FIG.  35    is a schematic elevation view of a substrate handler illustrating pitch control of the substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  36    is a schematic elevation view of one substrate handler passing by another substrate handler within a transport chamber in accordance with aspects of the disclosed embodiment; 
         FIG.  37    is a schematic elevation view of one substrate handler passing by another substrate handler within a transport chamber in accordance with aspects of the disclosed embodiment; 
         FIG.  38    is a schematic illustration of a portion of the actuator control system network showing dynamic phase allocation in accordance with aspects of the disclosed embodiment; 
         FIGS.  39 A and  39 B  illustrate tilt control of a portion of a substrate handler utilizing the actuator control system network with dynamic phase allocation and virtual multiphase actuator units in accordance with aspects of the disclosed embodiment; 
         FIG.  39 C  illustrates electrical phase angle control with the actuator control system network to effect independent propulsion and lift control of a substrate handler in accordance with aspects of the disclosed embodiment; 
         FIG.  40    is a schematic illustration of a clustered control architecture in accordance with aspects of the disclose embodiment; 
         FIG.  41 A  is a schematic illustration of a PVT frame in accordance with aspects of the disclosed embodiment; 
         FIG.  41 B  is a schematic illustration of a PVT-FG frame in accordance with aspects of the disclosed embodiment; 
         FIG.  42    is a flow chart of an exemplary method in accordance with aspects of the disclosed embodiment; 
         FIG.  43    is a flow chart of an exemplary method in accordance with aspects of the disclosed embodiment; 
         FIGS.  44 A,  44 B, and  44 C  are schematic illustrations portions of a transport chamber in accordance with aspects of the disclosed embodiment; 
         FIGS.  45 A,  45 B,  45 C, and  45 D  are schematic illustrations of portions of a transport chamber in accordance with aspects of the disclosed embodiment; 
         FIG.  46    is an exemplary graph of wafer handler temperature cycling in accordance with aspects of the disclosed embodiment; 
         FIGS.  47 A,  47 B, and  47 C  are schematic illustrations of a portion of a wafer handler in accordance with aspects of the disclosed embodiment; 
         FIGS.  48 A,  48 B, and  48 C  are schematic illustrations of a portion of a wafer handler in accordance with aspects of the disclosed embodiment; 
         FIGS.  49 A and  49 B  are exemplary graphs illustrating relationships between coil variables in accordance with aspects of the disclosed embodiment; 
         FIG.  50    is an exemplary graph illustrating coil current versus frequency in accordance with aspects of the disclosed embodiment; and 
         FIG.  51    is an exemplary flow diagram of a substrate transfer in accordance with aspects of the disclosed embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1 - 14    illustrate exemplary substrate processing apparatus  100 ,  100 A,  200 ,  300 ,  400 ,  500 ,  800 ,  900 ,  1200 ,  1300  in accordance with aspects of the disclosed embodiment. Although the aspects of the disclosed embodiment will be described with reference to the drawings, it should be understood that the aspects of the disclosed embodiment can be embodied in many forms. In addition, any suitable size, shape or type of elements or materials could be used. 
     Based on the problems and limitations of conventional substrate processing apparatus noted above, it is desirable to have a wafer (or substrate) handler  1500  that operates within a sealed environment, such as the substrate processing apparatus described herein, where an absolute position of a levitating body or base  1510  (also referred to as a reaction platen) of the wafer (or substrate) handler  1500  is tracked with a feedback apparatus that does not have a network of distributed sensors collocated within the substrate processing apparatus, that does not compete with actuator elements of the wafer handler  1500  for space within the substrate processing apparatus, that lacks sensors located in the sealed environment, and reduces the cost of the wafer handler/substrate processing apparatus compared to substrate processing apparatus noted above that employ tracking the position of the wafer handler with dedicated position feedback sensors. As will be described herein, the aspects of the present disclosure provide for a wafer handler  1500  and substrate processing apparatus that is/are configured to track the absolute positon of the base  1510  of the wafer handler  1500  with actuator coils of the wafer handler  1500 . For example, the alternating current voltage and resulting alternating current of the actuator coils are sampled to effect absolute position determination of the base  1510  without employing dedicated position feedback sensors and their associated wiring, complexity, and costs. Referring also to  FIGS.  15 A- 15 D , a wafer handler  1500  is part of linear electrical (or electric) machine  1599  (as will be described in greater detail herein and also referred to as an electromagnetic conveyor substrate transport apparatus) included in the substrate processing apparatus of  FIGS.  1 - 14   . Suitable examples of linear electrical machines can be found in U.S. patent application Ser. No. 17/180,298 titled “Substrate Processing Apparatus” and filed on Feb. 19, 2021, the disclosure of which is incorporated herein by reference in its entirety. The wafer handler  1500  includes a paramagnetic base  1510  (also referred to as a reaction platen, which in other aspects may be a diamagnetic base, or a base of non-magnetic conductive material, e.g., made of copper, aluminum or other suitable diamagnetic or nonmagnetic material that can induce Eddy currents) that is shaped to effect at least bi-directional linear induction propulsion along a direction of linear tracks  1550  formed by at least one linear induction motor stator  1560  (the at least one linear induction stator being formed by the array of electromagnets  1700  described herein), and independent rotation of the base  1510 . The wafer handler  1500  also includes an end-effector  1520  that is rigidly attached to the base  1510  (also referred to herein as a levitating body) and configured to stably hold substrates for transport throughout a respective chamber of a substrate processing apparatus. 
     The wafer handler  1500  is controlled by actuator control units, as will be described herein so that the configuration of the wafer handler  1500  is not dependent on stroke distances the wafer handler  1500  can cover (or extend). The independence of the wafer handler  1500  configuration  1500  is effected by utilizing a network of actuators  1700  (shown in and described in greater detail with respect to  FIGS.  17 - 28  and  40   ) that are physically distributed along at least a length of the substrate processing apparatus (such as along a length of a transport chamber  118 ) as will be described herein. In the aspects of the disclosed embodiment, the actuators  1700  are not tied to any specific substrate handler  1500 ; rather, the same actuators  1700  (are common to and) can control (and effect position determination of) multiple substrate handlers  1500  concurrently, which reduces cost of ownership of the substrate handlers  1500  as the substrate handlers  1500  may be added to or removed from a substrate processing apparatus without adding additional actuators. Concurrent control and position determination of multiple substrate handlers  1500  with common actuators  1700  is effected by a control system in accordance with the aspects of the disclosed embodiment (described in greater detail below) that is configured to dynamically allocate the excitation phase of each actuator coil unit (also referred to as an electromagnet) of the common actuators  1700  between different excitation phases in a manner that provides continuity of force vectors for performing wafer handler motion in a three-dimensional space with control of up to six degrees of freedom from the common (set) of actuators  1700 . As will be described herein, the concurrently controlled substrate handlers  1500  may be controlled in roll, pitch, and/or yaw to allow two or more independently operated substrate handlers  1500  to decrease a distance between the substrate handlers  1500  by tilting each (or at least one) of the substrate handlers  1500  along a rotation axis substantially parallel to the motion thrust direction (see, e.g.,  FIG.  37   ). 
     As noted above, conventional robotic manipulators with articulated links require substantially different mechanical designs as the required stroke of the manipulators is increased in order to reach a larger number of process modules, which increases the cost of the robotic manipulators and may shorten robotic manipulator service intervals. Contrary to conventional substrate handling systems, the aspects of the disclosed embodiment are highly scalable when compared to existing commonly accepted substrate handling solutions (such as those described above) without adding complexity and reliability concerns resultant from an increased number of mechanical components and/or sensors distributed throughout the substrate processing tool for determining a position of the wafer handler  1500 . 
     As will be described in greater detail herein, the aspects of the disclosed embodiment provide for a magnetic levitated substrate transport apparatus based on linear induction technology that is configured to provide lift, lateral stabilization, and propulsion to the wafer handler  1500 , while providing self-deterministic absolute position feedback of the wafer handler  1500  by employing the electromagnets (also referred to as actuator coils or coils) of the wafer handler  1500  for position determination. Aspects of the disclosed embodiment also provide for a linear induction motor stator operating in and forming independently controlled linear tracks that are orthogonal or otherwise angled at an orientation between being substantially parallel and substantially orthogonal and/or forming arcuate or rotary paths over a two-dimensional area. As will be described herein, these tracks are formed by an array of electromagnets (e.g., an actuator coil grid or matrix)  1700  (see also  FIG.  18   ) configured to both propel the wafer handler  1500  for wafer transport and effect position determination of the wafer handler  1500 . The aspects of the disclosed embodiment provide a coil controller that is configured to generate alternating current at a prescribed frequency and amplitude for each phase of each linear induction motor stator associated with a respective linear track  1550 . The propulsion forces provided by the linear tracks are controlled so as to rotate the base  1510 , independent of linear movement of the base along the tracks, where the propulsion forces generate a moment load around an axis of rotation of the base  1510 . The aspects of the disclosed embodiment also provide for the coil controller being configured, as will be described herein, to sample at least the alternating current and alternating current voltage for determining the absolute position of the wafer handler as described herein. 
     The aspects of the disclosed embodiment include a control system configured to track a position of the base  1510  and control the phase currents of the independent linear tracks  1550  (e.g., formed by the array of electromagnets  1700 ) for controlling motion of the base  1510  along a desired propulsion direction along the independent linear tracks  1550 . The control system, in accordance with aspects of the disclosed embodiment, also provides for motion of the base  1510  in a lift direction while maintaining lateral stabilization of the base  1510 . The control system is configured to generate propulsion forces with the linear tracks  1550  so as to control roll, pitch, and yaw of the substrate handler  1500 , where the roll, pitch, and yaw motions of the substrate handler  1500  may be employed to maximize substrate production throughput by adjusting an inclination of the substrate handler  1500  (see, e.g.,  FIG.  21   ) depending on a desired acceleration of the substrate handler  1500  in linear and/or rotation directions of motion, so as to increase the acceleration threshold along a thrust direction of the substrate handler  1500 . 
     Referring to  FIG.  1 A , there is shown a schematic plan view of a substrate processing apparatus  100  incorporating aspects of the disclosed embodiment. The substrate processing apparatus  100  is connected to an environmental front end module (EFEM)  114  which has a number of load ports  112  as shown in  FIG.  1 A . The load ports  112  are capable of supporting a number of substrate storage canisters  171  such as for example conventional FOUP canisters; though any other suitable type may be provided. The EFEM  114  communicates with the processing apparatus through load locks  116  which are connected to the processing apparatus as will be described further below. The EFEM  114  (which may be open to atmosphere) has a substrate transport apparatus (not shown—but in some aspects is similar to the linear electrical machine  1599  described herein, e.g., the linear electrical machine described herein may be employed in vacuum and atmospheric environments) capable of transporting substrates from load ports  112  to load locks  116 . The EFEM  114  may further include substrate alignment capability, batch handling capability, substrate and carrier identification capability or otherwise. In other aspects, the load locks  116  may interface directly with the load ports  112  as in the case where the load locks have batch handling capability or in the case where the load locks have the ability to transfer wafers directly from the FOUP to the lock. Some examples of such apparatus are disclosed in U.S. Pat. Nos. 6,071,059, 6,375,403, 6,461,094, 5,588,789, 5,613,821, 5,607,276, 5,644,925, 5,954,472, 6,120,229, and 6,869,263 all of which are incorporated by reference herein in their entirety. In other aspects, other load lock options may be provided. 
     Still referring to  FIG.  1 A , the processing apparatus  100 , may be used for processing semiconductor substrates (e.g. 200 mm, 300 mm, 450 mm, or other suitably sized wafers), panels for flat panel displays, or any other desired kind of substrate, generally comprises transport chamber  118  (which in one aspects holds a sealed atmosphere therein), processing modules  120 , and at least one substrate transport apparatus or linear electrical machine  1599 . The substrate transport apparatus  1599  in the aspect shown may be integrated with the chamber  118  or coupled to the chamber in any suitable manner as will be described herein. In this aspect, processing modules  120  are mounted on both sides of the chamber  118 . In other aspects, processing modules  120  may be mounted on one side of the chamber  118  as shown for example in  FIG.  2   . In the aspect shown in  FIG.  1 A , processing modules  120  are mounted opposite each other in rows Y 1 , Y 2  or vertical planes. In other aspects, the processing modules  120  may be staggered from each other on the opposite sides of the transport chamber  118  or stacked in a vertical direction relative to each other. Referring also to  FIGS.  15 A- 15 C and  18   , the transport apparatus  1599  has substrate handler  1500  that is moved in the chamber  118  to transport substrates between load locks  116  and the processing chambers  120 . In the aspect shown, only one substrate handler  1500  is provided; however, in other aspects more than one substrate handler may be provided. As seen in  FIG.  1 A , the transport chamber  118  (which is subjected to vacuum or an inert atmosphere or simply a clean environment or a combination thereof in its interior) has a configuration, and employs the substrate transport apparatus  1599  that allows the processing modules  120  to be mounted to the chamber  118  in a Cartesian arrangement with processing modules  120  arrayed in substantially parallel vertical planes or rows. This results in the processing apparatus  100  having a more compact footprint than a comparable conventional processing apparatus, such as those described herein. Moreover, the transport chamber  118  may be capable of being provided with any desired length (i.e., the length is scalable) to add any desired number of processing modules  120 , as will be described in greater detail below, in order to increase throughput. The transport chamber  118  may also be capable of supporting any desired number of transport apparatus  1599  therein and allowing the transport apparatus  1599  to reach any desired processing chamber  120  coupled to the transport chamber  118  without interfering with each other. This in effect decouples the throughput of the processing apparatus  100  from the handling capacity of the transport apparatus  1599 , and hence the processing apparatus  100  throughput becomes processing limited rather than handling limited. Accordingly, throughput can be increased as desired by adding processing modules  120  and corresponding handling capacity on the same platform. 
     Still referring to  FIG.  1 A , the transport chamber  118  in this aspect has a general rectangular shape though in other aspects the chamber may have any other suitable shape. The chamber  118  has a slender shape (i.e. length much longer than width) and defines a generally linear transport path for the transport apparatus  1599  therein. The chamber  118  has longitudinal side walls  118 S. The side walls  118 S have transport openings or ports  1180  (also referred to as substrate pass through openings) formed therethrough. The transport ports  1180  are sized large enough to allow substrates to pass through the ports (which ports can be sealable by valves) into and out of the transport chamber  118 . As can be seen in  FIG.  1 A , the processing modules  120  in this aspect are mounted outside the side walls  118 S with each processing module  120  being aligned with a corresponding transport port  1180  in the transport chamber  118 . As can be realized, each processing module  120  may be sealed against the sides  118 S of the chamber  118  around the periphery of the corresponding transport aperture to maintain the vacuum in the transport chamber. Each processing module  120  may have a valve, controlled by any suitable means, such as controller  199 , to close the transport port when desired. The transport ports  1180  may be located in the same horizontal plane. Accordingly, the processing modules on the chamber are also aligned in the same horizontal plane. In other aspects, the transport ports  1180  may be disposed in different horizontal planes. As seen in  FIG.  1 A , in this aspect, the load locks  116  are mounted to the chamber sides  118 S at the two front most transport ports  1180 . This allows the load locks  116  to be adjacent the EFEM  14  at the front of the processing apparatus. In other aspects, the load locks  116  may be located at any other transport ports  1180  on the transport chamber  118  such as shown for example in  FIG.  2   . The hexahedron shape of the transport chamber  118  allows the length of the chamber to be selected as desired in order to mount as many rows of processing modules  120  as desired (for example see  FIGS.  1 B,  3 ,  4 - 7    showing other aspects in which the transport chamber  118  length is such to accommodate any number of processing modules  120 ). 
     As noted before, the transport chamber  118  in the aspect shown in  FIG.  1 A  has a substrate transport apparatus  1599  having a single substrate handler  1500 . The transport apparatus  1599  is integrated with the chamber  118  to translate substrate handler  1500  back and forth in the chamber  118  between front  118 F and back  118 R. The substrate handler  1500  of the substrate transport apparatus  1599  has at least one end effector  1520  for holding one or more substrates. 
     It should be understood that the transport apparatus  1599 , shown in  FIG.  1 A  (also referring to  FIGS.  44 A- 44 C ) is a representative transport apparatus and, includes the substrate handler  1500  (a portion of which is illustrated in  FIGS.  44 B,  44 C  for clarity) which is magnetically supported from the linear tracks  1550  formed by the array of electromagnets  1700 . The transport apparatus  1599  will be described in greater detail below. The transport chamber  118  may form a frame  118 M (see  FIG.  1 A ) with a level reference plane  1299 , e.g., that defines or otherwise corresponds (e.g., is substantially parallel) with a wafer transport plane  1290  (see  FIG.  12 B ). The linear tracks  1550  formed by array of electromagnets  1700  may be mounted to the side walls  118 S or floor  118 L of the transport chamber  118  (where the floor  118 L forms a non-magnetic isolation wall between the array of electromagnets  170  and the wafer handler  1500 ) and may extend the length of the chamber  118 . This allows the wafer handler  1500  to traverse the length of the chamber  118 . As will be described in greater detail below the array of electromagnets  1700  (also referred to herein as actuators  1700 ) form the linear tracks  1550  of  FIG.  1 A , where each of linear tracks  1500  includes a respective array of electromagnets or actuators  1700 A- 1700   n . The array of electromagnets or actuators  1700 A- 1700   n  are referred to herein as a network of actuators as in  FIGS.  14 A,  15 A,  15 B,  16 B,  16 C,  17   , and  18  (e.g., that form at least one linear induction motor stator  1560 —noting that in  FIGS.  14 A- 16 C  there are two rows of electromagnets illustrated for each drive line  177 - 180  for clarity of illustration but it should be understood that more than two rows of electromagnets may be provided per drive line as illustrated in  FIG.  18    (see also  FIGS.  44 A- 44 C ), where one or more electromagnets are common to more than one drive line), connected to the transport chamber  118  to form a drive plane  1598  at a predetermined height H relative to the reference plane  1299 , the array of electromagnets  1700  (see also  FIG.  18   ) being arranged so that a series of the electromagnets  1700 A- 1700   n  define at least one drive line within the drive plane  1598 , and each of the electromagnets  1700 A- 1700   n  (see  FIG.  15 B ) in the array of electromagnets  1700  being coupled to an alternating current (AC) power source  1585  energizing each electromagnet  1700 A- 1700   n , where the alternating power source is, in one aspect, a three phase (or more) alternating current power source. As noted above (see  FIG.  15 A ), the base or reaction platen  1510  is formed of a paramagnetic, diamagnetic, or non-magnetic conductive material disposed to cooperate with the electromagnets  1700 A- 1700   n  of the array of electromagnets  1700  so that excitation of the electromagnets  1700 A- 1700   n  with alternating current from the alternating current source  1585  generates levitation forces FZ and propulsion forces FP (see  FIG.  21   ) against the base  1510  that controllably levitate and propel the base  1510  along the at least one drive line  177 - 180  (see, e.g.,  FIGS.  1 - 8   ), in a controlled attitude relative to the drive plane  1598 . 
     As noted above, the chamber floor  118 L forms a non-magnetic isolation wall  4400  (see  FIGS.  44 A- 44 C ) between the array of electromagnets  1700  and the wafer handler  1500 . Here the array of electromagnets  1700  are disposed in an atmospheric environment while the wafer handler  1500  is disposed in a vacuum environment of the transport chamber  118 . The non-magnetic isolation wall  4400  (and the chamber floor  118 L) is selected so as to have a low electrical conductivity and a high resistivity to minimize the occurrence of Eddy Currents (and minimize magnetic field losses due to the Eddy Currents) while allowing a magnetic field to pass through the non-magnetic isolation wall  4400  to establish a magnetic circuit between the (e.g., coils/poles) of the electromagnets in the array of electromagnets  1700  and the base  1510  of the wafer handler  1500 . Suitable examples of materials from which the non-magnetic isolation wall  4400  (and the floor  118 L) include materials that are vacuum compatible and have a high resistivity, high stiffness, high yield strength, and high thermal conductivity such as, for example, 300-Series Stainless Steel that conforms with the electrical and magnetic (e.g., non-magnetic) properties noted above. A Suitable example of the 300-series Stainless Steel includes, but is not limited to, 304 Stainless Steel. In one aspect, the chamber floor  118 L a separate (i.e., different) material than that of the frame  118 M such as to reduce costs of the transport chamber  118  structure. For example, the frame  118 M may be constructed of aluminum (or other suitable material) while the floor  118 L is constructed of stainless steel (or other suitable material). Other suitable examples of material from which the non-magnetic isolation wall  4400  (and the floor  118 L) may be constructed includes, but is not limited to, low conductivity aluminum such as a 6061 series aluminum (e.g., 6061-F, 6061-0, 6061-O, 6061-T4, 6061-T6, and 6061-T9). 
     With respect to the magnetic circuit formed between the (e.g., coils/poles) of the electromagnets in the array of electromagnets  1700  and the base  1510  of the wafer handler  1500 , the base  1510  is constructed of any suitable paramagnetic material. The paramagnetic material of the base  1510  has a low resistivity so as maximize induction of Eddy Currents, a low mass density to minimize weight of the base  1510 , and be inert so as to be vacuum compatible and resistant at high temperatures (e.g., such as about 100° C. or more). Suitable examples of materials from which the base  1510  may be constructed include, but are not limited to, 1100 series Aluminum Alloy (such as the 1100, 1100-O, and 1100-H18 Aluminum Alloys), and 6101 series Aluminum Alloy (such as the 6101-T6, 6101-T61, 6101-T63, 6101-T64, and 6101-T65 Aluminum Alloys). It is noted that for atmospheric applications of the transport described herein, the base  1510  may be constructed of copper or any of the other materials described herein for the base  1510 . 
     The poles  4500 P (see, e.g.,  FIGS.  45 A- 45 C ) of the electromagnets and the coil base plate are ferromagnetic and have a high magnetic permeability, high magnetic saturation, and high electrical resistivity (e.g., so as to minimize Eddy Currents) so as to maximize levitation efficiency for levitating the base  1510 . As described herein, the poles and the coil base plate may be constructed of any suitable soft magnetic composite (SMC) material with a magnetic saturation reaching about 2 Tesla. A suitable example of a soft magnetic composite material being, but not limited to, Hoganas&#39; 700HR 5P. 
     Referring also to  FIG.  50   , an exemplary graph illustrating coil current versus frequency is illustrated with respect to Eddy Current loses. The graph shows finite element electromagnetic model analysis of several materials (e.g., the SMC materials noted above and stainless steel, such as the stainless steels described herein) from which the coil base plate and poles  4500 P may be constructed. The graph illustrates modelling conditions where the Eddy Currents are turned off in the poles, the Eddy Currents are turned off in the coil base plate, the Eddy Currents are off in both the poles and the coil base plate, and the Eddy Currents are turned on in both the poles and the coil base plate. The graph illustrates a substantial elimination of Eddy Current loses with both the poles  4500 P and the coil base plate constructed of the soft magnetic composite material, e.g., when compared to model conditions with the poles constructed of the SMC material and the coil base plate is constructed of stainless steel and to model conditions with the both the poles and the coil base plate constructed of stainless steel. Here, constructing both the poles and the coil base plate with the soft magnetic composite material provides for maximization of coil current given a predetermined voltage (e.g., in this analysis the peak (maximized) current is about 8.2 A with a voltage of about 43.2V). 
     Referring to  FIGS.  45 A- 45 C , in one or more aspects, the array of electromagnets  1700  may be modular and include array modules  1700 M. The array modules  1700 M include electromagnetic elements  4500  that are modularly coupled to the coil base plate in any suitable manner (such as, e.g., with any suitable retainers/fasteners) as illustrated in  FIG.  45 A . In other aspects, the electromagnetic elements  4500  may be integrally formed with the coil base plate. Each electromagnet element  4500  includes a base  4500 B, a coil  4500 C, and a pole  4500 P. The pole  4500 P may be monolithic, or in other aspects, constructed of more than one part  4500 P 1 ,  4500 P 2  that are coupled to each other (illustrated in  FIG.  45 D ) to form a respective pole  4500 P. Electrical continuity may be effected between the electromagnetic elements  4500  through abutting contact between adjacent bases  4500 B and/or through the coil base plate. The poles  4500 P, the base  4500 B, and the coil base plate may be constructed of any suitable material such as any suitable soft magnetic composite (SMC) material. Here, each (or one or more) of the array modules  1700 M may be removed from the transport chamber  118  for maintenance without disruption of the vacuum integrity/environment within the transport chamber  118  as the array modules are disposed on the atmospheric side of the non-magnetic isolation wall  4400  (e.g., the chamber floor  118 L). 
       FIG.  1 B  shows another aspect of a substrate processing apparatus  100 A which is generally similar to apparatus  100 . In this aspect, the transport chamber  118  has two substrate handlers  1500 A,  1500 B independently operated by the array of electromagnets  1700  (as in  FIG.  16 C ). The substrate handlers  1500 A,  1500 B are substantially the same as the substrate handler  1500  previously described. Both of the substrate handlers  1500 A,  1500 B may be supported from a common array of electromagnets  1700  as described before. The base  1510  of each substrate handler  1500 A,  1500 B may be driven by the same at least one linear induction motor stator  1560  as will be described herein, by individually controlling each coil element or electromagnet  1700 A- 1700   n  (as in  FIG.  15 B ). Thus, as can be realized the end effector  1520  each substrate handler  1500  can be independently moved in linear movement and/or rotation using the at least one linear induction motor stator  1560 . However, in this aspect the substrate handlers  1500 A,  1500 B are not capable of passing each other in the transport chamber  118  as the transport chamber  118  includes but one drive line  177  (compared to transport chambers having multiple substantially parallel drive lines as shown in  FIGS.  8 - 10   ). Accordingly, the processing modules  120  are positioned along the length of the transport chamber  118  so that the substrate may be transported to be processed in the processing module in a sequence which would avoid the substrate handlers  1500 A,  1500 B from interfering with each other. For example, processing modules for coating may be located before heating modules, and cooling modules and etching modules may be located last. 
     However, referring to  FIGS.  8 - 10   , the transport chamber  118  may have any suitable width to provide for two or more substantially parallel drive lines  177 ,  178  (e.g., formed by the array of electromagnets  1700 ) that extend at least along a portion of a longitudinal length of the transport chamber  118  so that the two substrate handlers  1500 A,  1500 B pass adjacent each other (akin to a side rail or bypass rail). In the aspects illustrated in  FIGS.  8 - 10    the transport apparatus  1599  has two drive lines  177 ,  178  but in other aspects any suitable number of substantially parallel longitudinally extending drive lines may be provided. 
     In accordance with some aspects of the disclosed embodiment, the array of electromagnets  1700  (or at least a portion thereof) may also be used as heater for the wafer handler (e.g., so as to control heating of the reaction platen and/or wafer to a desired predetermined temperature and for a desired predetermined time) as in the case where it is desired to eliminate water vapor (e.g., gas) or potentially pre-heat the wafer/substrate picked from, e.g., a load port en route to a process module or alternatively reduce thermal gradient between the wafer at the process module and the wafer handler end effector. The heating of the wafer handler may be effected with the reaction platen in transit or with the reaction platen held static in a predetermined location/position. Still In accordance with some aspects of the disclosed embodiment, the array of electromagnets  1700  (or at least a portion thereof) may also be used as heaters as in the case where it is desired that the transport chamber  118  be heated for degas as in the case to eliminate water vapor for example. Controlled heating of the transport chamber  118  to a predetermined temperature for a predetermined time may be with the reaction platen static. 
     In accordance with the aspects of the disclosed embodiment, the controller  199  of the substrate processing apparatus described herein is configured with a predetermined platen temperature management protocol PTMP (see  FIG.  1   ) that effects temperature control (e.g., thermal management) of the base  1510  of the wafer handler  1500 . Here, the base  1510  is thermally managed so as to maintain a predetermined levitation efficiency. As may be realized, with the base  1510  levitating, Eddy Currents induced in the base  1510  will generate heat and the temperature of the base  1510  will rise. An increase in temperature of the base  1510  may increase the electrical resistivity of the base  1510 , which in turn may reduce the induction of Eddy Currents and the levitation force exerted on the base  1510  by the array of electromagnets  1700 . Any suitable controller, such as controller  199  (described herein) is configured with the predetermined platen temperature management protocol PTMP to effect a base  1510  cooling cycle to maintain the base  1510  within a predetermined temperature range (such as below about 100° C.). For example, the predetermined platen temperature management protocol PTMP controls the temperature of the base  1510  vie (e.g., with) conduction from the base  1510  to a thermal sink  4444  (see  FIG.  44 A  which may be the floor  118 L or isolation wall  4400 ) commensurate (e.g., in time) with at least a wafer swap operation of the base  1510  (and the wafer handler  1500  thereof). Here, the controller  199  may activate (or deactivate) the array of electromagnets  1700  (or a portion thereof) so that the base  1510  lowers to seat on (e.g., lands on) the floor  118 L of the transport chamber  118  where heat is removed from the base  1510  by the floor  181 L via conduction from the base through the floor  118 L) (e.g., the isolation wall) towards the atmospheric side of the floor  118 L where the coils  4500 C, poles  4500 P, and coil base plate are disposed. 
     In one or more aspects, the cooling of the base  1510  may occur opportunistically such as with a wafer exchange operation (e.g., a swapping or transfer of one or more wafers at a wafer holding station as noted above). For example, where wafer handler  1500  includes at least two end effectors  1520 , one of the end effectors  1520  waits or sits idle while the another of the at least two end effectors  1520  completes a pick/place operation. With the other end effector  1520  picking/placing the wafer, the idle end effector  1520  is seated on the floor  118 L to cool off the base  1510 . In other aspects, the controller  199  may command cooling of the base  1510  of the wafer handler  1500  (having one or more end effectors) at any suitable time. 
     Other thermal management solutions for cooling the base  1510  of the wafer handler  1500  that may be employed with the aspects of the disclosed embodiment include a wafer handler replacement (e.g., the wafer handler  1500  is replaced in its entirety) without disrupting the vacuum environment within the transport chamber  118 . For example, a “service lock” SL (see  FIG.  1   ) is substantially similar to load lock  116  but with a floor similar to the transport chamber  118 L (so that the wafer handler transitions between the transport chamber and service lock). The service lock SL also has sealable opening  1180 T shaped and sized for passage of the wafer handler therethrough. 
     The service lock SL has a frame SLF that is shaped and sized so that one wafer transport  1500  (and the reaction platen or base  1510  thereof) may be replaced with another wafer transport  1500 ALT (and the other reaction platen or base  1510 ALT thereof). Here, the other base  1510 ALT, is alternative to the base  1510 , and is held inactive within the service lock SL so as to be in a cold state, relative to the temperature of the base  1510  in its operative state. Here, the predetermined platen temperature management protocol PTMP includes the other base  1510  (and the wafer handler  1500 ALT thereof) being switched to an operative state (so that the base  1510  is levitated) and replacing the base  1510  (and the wafer handler  1500  thereof), at its temperature limits. For example, the wafer handler  1500  is commanded to move into the service lock SL and is placed in an inactive state (so the base  1510  is seated on the floor  118 L of the service lock SL. The other wafer handler  1500 ALT is placed in an operative state so as to levitate and is commanded to move into the transport chamber  118  for wafer handling/transfer operations. 
     In other aspects, the service lock SL may be configured to introduce wafers (and/or wafer handlers) into the processing system. For example, the service lock SL may include a door that is shaped and sized so that an operator of the processing system may insert/remove one or more of wafers (for placement on a wafer handler disposed in the service lock SL) and wafer handlers (loaded with a wafer or unloaded) to and from the service lock SL. Here the wafers may be introduced into the processing system without the wafers being transported to the processing system in a FOUP  171 . 
     The service lock SL can be added to or otherwise integrated with the transport chamber  118 . Here, a wafer handler  1500  within the isolated environment of the service lock SL provides for the wafer handler  1500  to be periodically (or at any suitable intervals which may be preset or determined based on a temperature of the wafer handler) removed and replaced with another wafer handler  1500 ALT that is clean and cooler than the removed wafer handler  1500 . 
       FIG.  46    illustrates exemplary vacuum temperature transients of the wafer handler  1500  base  1510  versus time.  FIG.  46    illustrates that the base  1510  (and the wafer handler  1500 ) can operate at over about 90% duty cycle levitation while maintaining the base  1510  within a temperature range of about 50° C. to about 100° C., which maintains the levitation efficiency within a predetermined range. 
     Referring now to  FIGS.  4  and  5    there are shown other substrate processing apparatus  400 ,  500  in accordance with other aspects of the disclosed embodiment. As seen in  FIGS.  4  and  5    the transport chamber(s)  118 ,  118 A,  118 B,  118 C in these aspects is elongated to accommodate additional processing modules  120 . The apparatus shown in  FIG.  4    has twelve (12) processing modules  120  connected to the transport chamber  118 . The processing apparatus  500  in  FIG.  5    is illustrated as having two transport chambers  118 A,  118 B coupled to each other by a bridging chamber  118 C that provides for movement of the substrate handlers  1500  between the transport chambers  118 A,  118 B. Here, each transport chamber  118 A,  118 B in  FIG.  5    has 24 processing modules  120  connected thereto. The numbers of processing modules  120  shown in these aspects are merely exemplary, and the substrate processing apparatus may have any other number of processing modules  120  as previously described. The processing modules  120  in these aspects are disposed along the sides of the respective transport chamber  118 A,  118 B in a Cartesian arrangement similar to that previously discussed. The number of rows of processing modules  120  in these aspects, however have been greatly increased (e.g. six (6) rows in the apparatus of  FIG.  4   , and twelve (12) rows in each of the apparatus of  FIG.  5   ). In the aspect shown in  FIG.  4   , the EFEM may be removed and the load ports  112  may be mated directly to the load locks  116 . The transport chambers of the substrate processing apparatus  400 ,  500  in  FIGS.  4 , and  5    may have multiple substrate handlers  1500  to handle the substrates between the load locks  116  and the processing chambers  120 . The number of substrate handlers  1500  shown is merely exemplary and more or fewer apparatus may be used. The substrate transport apparatus  1599  (a portion of which is illustrated in  FIGS.  4  and  5   ) in these aspects are generally similar to that previously described, comprising the linear tracks  1550  and substrate handler(s)  1500 . In the aspects shown in  FIGS.  4  and  5   , while only a single longitudinal drive line (e.g., drive lines  177 ,  178 ,  179  is illustrated in each chamber  118 ,  118 A,  118 B,  118 C, it should be understood that in other aspects multiple drive lines may longitudinally extend along each chamber  118 ,  118 A,  118 B,  118 C in a manner substantially similar to that illustrated in  FIGS.  8 - 10   . As can be realized, as with the other substrate transport apparatus  100 ,  100 A,  200 ,  300 ,  800 ,  900 ,  1200 ,  1300  described herein, the substrate transport apparatus  400 ,  500  has a controller  199  for controlling the movements of the one or more substrate handlers  1500  of the substrate transport apparatus  1599 . 
     Still referring to  FIG.  5   , the transport chambers  118 A,  118 B in this case may be mated directly to a tool  300  (e.g., a stocker, photolithography cell, or other suitable processing tool) where the substrates are delivered to and removed from the tool  300  through chamber  118 C. 
     As may be realized from  FIGS.  1 B,  3  and  4 - 5    the transport chamber  118  may be extended as desired to run throughout the processing facility P (see  FIG.  5   , and an example processing facility is illustrated in  FIG.  7   ). As seen in  FIG.  5   , and as will be described in further detail below, the transport chamber (generally referred to as transport chamber  118 ) may connect and communicate with various sections or bays  118 P 1 - 118 P 4  in the processing facility P such as for example storage, lithography tool, metal deposition tool or any other suitable tool bays. Bays interconnected by the transport chamber  118  may also be configured as process bays or processes  118 P 1 ,  118 P 3 . Each bay has desired tools (e.g. lithography, metal deposition, heat soaking, cleaning) to accomplish a given fabrication process in the semiconductor workpiece. In either case, the transport chamber  118  has processing modules  120 , corresponding to the various tools in the facility bays, communicably connected thereto, as previously described, to allow transfer of the semiconductor workpiece between chamber  118  and processing modules  120 . Hence, the transport chamber  118  may contain different environmental conditions such as atmospheric, vacuum, ultra-high vacuum (e.g., 10-5 Torr), inert gas, or any other, throughout its length corresponding to the environments of the various processing modules connected to the transport chamber. Accordingly, the section  118 P 1  of the chamber in a given process or bay or within a portion of the bay, may have for example, one environmental condition (e.g. atmospheric), and another section  118 P 2 ,  118 P 3  of the chamber  118  may have a different environmental condition. As noted before, the section  118 P 1 - 118 P 4  of the chamber  118  with different environments therein may be in different bays of the facility, or may all be in one bay of the facility.  FIG.  5    shows the chamber  118  having four sections  118 P- 118 P 4  with different environments for example purposes only. The chamber  118  in this aspect may have as many sections with as many different environments as desired. 
     As seen in  FIG.  5   , the substrate handlers  1500  in the transport chamber  118  are capable of transiting between sections  118 P 1 - 118 P 4  of the chamber  118  with different environments therein. Hence, as can be realized from  FIG.  5   , each of the substrate handlers  1500  may with one pick move a semiconductor workpiece from the tool in one process or bay of the processing facility to another tool with a different environment in a different process or bay of the process facility. For example, substrate handler  1500 A may pick a substrate in processing module  301 , which may be an atmospheric module, lithography, etching, or any other desired processing module in section  118 P 1 , of transport chamber  118 . The substrate handler  1500 A may then move along drive line  177  (or a drive line substantially parallel thereto where more than one longitudinal drive line are provided) from section  118 P 1  of the chamber  118  to section  118 P 3  (e.g., where the other substrate handlers  1500  are controlled to avoid interference with substrate handler  1500 A in any suitable manner, such as described herein). In section  118 P 3 , the substrate handler  1500 A may place the substrate in processing module  302 , which may be any desired processing module. 
     As can be realized from  FIG.  5   , the transport chamber  118  may be modular, with chamber modules connected as desired to form the chamber  118  (e.g., formed by the three chamber sections  118 A,  118 B,  118 C, where each chamber section  118 A,  118 B,  118 C may also include one or more chamber modules that are coupled to each other in any suitable manner). Referring also to  FIG.  1 A , the modules may include internal walls  1181 , similar to walls  118 F,  118 R in  FIG.  1 A , to segregate sections  118 P 1 - 118 P 4  of the chamber  118 . Internal walls  181  may include slot valves, or any other suitable valve allowing one section of the chamber  118 P 1 - 118 P 4  to communicate with one or more adjoining sections. The slot valves  118 V, may be sized to allow, one or more substrate handlers  1500  to transit through the valves  18 V from one section  118 P 1 - 118 P 4  to another. In this way, the substrate handlers  1500  may move anywhere throughout the chamber  118 . The valves  118 V may be closed to isolate sections  118 P 1 - 1184  of the chamber  118  so that the different sections may contain disparate environments as described before. Further, the internal walls  1181  of the chamber modules may be located to form load locks (see section  118 P 4 ) as shown in  FIG.  5   . The load locks  118 P 4  (only one is shown in  FIG.  5    for example purposes) may be located in chamber  118  as desired and may hold any desired number of substrate handlers  1500  therein. 
     In the aspect shown in  FIG.  5   , processes within chamber sections  118 A and  118 B may be the same processes, for example etch, where the processing apparatus  500  including tool  300  (such as a stocker) are capable of processing substrates without any associated material handling overhead associated with transporting FOUPS from the stocker to individual process modules  120  via an automated material handling system, and transporting individual wafers via EFEM&#39;s to the respective processing modules  120 . Instead, a robot within the stocker directly transfers FOUPS  171  to the load ports (three load ports are shown per chamber section, more or less could be provided depending on throughput requirements) where the wafers are batch moved into locks and dispatched to their respective process module(s) depending on the desired process and/or throughput required. The chamber sections  118 A,  118 B or the stocker  300  may further have metrology capability, sorting capability, material identification capability, test capability, inspection capability, etc. as required to effectively process and test substrates. 
     In the aspect of the disclosed embodiment shown in  FIG.  5   , more or less chamber sections  118 A and  118 B may be provided that have different processes, for example etch, CMP, copper deposition, PVD, CVD, etc. where the chamber sections  118 A,  118 B, etc. in combination with the tool  300  being, for example a photolithography cell are capable of processing substrates without the associated material handling overhead associated with transporting FOUPs from stockers to individual process tool bays and a lithography bay via an automated material handling system, and transporting individual wafers via EFEM&#39;s to the respective processing tools. Instead, the automation within the lithography cell directly transfers FOUPS, substrates or material to the load ports  112  (again three load ports are shown per chamber section/process type, noting more or less could be provided depending on throughput requirements) where the substrates are dispatched to their respective process depending on the desired process and/or throughput required. An example of such an alternative is shown in  FIG.  7   . In this manner, the apparatus in  FIG.  5    processes substrates with less cost, lower footprint, less WIP required (compared to the conventional processing systems described herein)—therefor with less inventory and with a quicker turnaround when looking at the time to process a single carrier lot (or “hot lot”), and with a higher degree of contamination control resulting in significant advantages for the fabrication facility operator. The chamber sections  118 A,  118 B (each of which may be referred to as a tool or tool section) or the tool or cell  300  may further have metrology capability, processing capability, sorting capability, material identification capability, test capability, inspection capability, etc. as required to effectively process and test substrates. As can be realized from  FIG.  5   , the chamber sections  118 A,  118 B, and tool  300  may be coupled to share a common controlled environment (e.g. inert atmosphere, or vacuum). This ensures that substrates remain in a controlled environment from tool  300  and throughout the substrate processing apparatus  500 . This eliminates use of special environment controls of the FOUPs as in conventional substrate processing apparatus such as those shown in  FIGS.  37  and  38   . 
     Referring now to  FIG.  7   , there is shown an exemplary fabrication facility layout  601  incorporating aspects of the disclosed embodiment that are shown in  FIG.  5   . Wafer handlers  406 , similar to wafer handlers  1500  transport substrates or wafers through process steps within the fabrication facility  601  through transport chambers  602 ,  604 ,  606 ,  608 ,  610 ,  612 ,  614 ,  616 ,  618 ,  620 ,  624 ,  626 . Process steps may include epitaxial silicon  630 , dielectric deposition  632 , photolithography  634 , etching  636 , ion implantation  638 , rapid thermal processing  640 , metrology  642 , dielectric deposition  644 , etching  646 , metal deposition  648 , electroplating  650 , chemical mechanical polishing  652 . In other aspects, more or less processes may be involved or mixed; such as etch, metal deposition, heating and cooling operations in the same sequence. As noted before, wafer handlers  406  may be capable of carrying a single wafer or multiple wafers and may have transfer capability, such as in the case where wafer handler  406  has the capability to pick a processed wafer and place an unprocessed wafer at the same module. Wafer handlers  406  may travel through isolation valves  654  for direct tool to tool or bay to bay transfer or process to process transfer. Valves  654  may be sealed valves or simply conductance type valves depending upon the pressure differential or gas species difference on either side of a given valve  654 . In this manner, wafers or substrates may be transferred from one process step to the next with a single handling step or “one touch”. As a result, contamination due to handling is minimized. Examples of such pressure or species difference could be for example, clean air on one side and nitrogen on the other; or roughing pressure vacuum levels on one side and high vacuum on the other; or vacuum on one side and nitrogen on the other. Load locks  656 , similar to chambers  118 P 4  in  FIG.  5   , may be used to transition between one environment and another; for example between vacuum and nitrogen or argon. In other aspects, other pressures or species may be provided in any number of combinations. Load locks  656  may be capable of transitioning a single wafer handler or multiple wafer handlers in a manner substantially similar to that described herein where a single drive line or multiple substantially parallel and/or orthogonal drive lines are provided. Alternately, substrate(s) may be transferred into load lock  656  on shelves (not shown) or otherwise where the wafer handler  406  is not desired to pass through the valve. Additional features  658  such as alignment modules, metrology modules, cleaning modules, process modules (ex: etch, deposition, polish, etc.), thermal conditioning modules or otherwise, may be incorporated in lock  656  or the transport chambers. Service ports  660  may be provided to remove wafer handlers  406  or wafers from the tool. Wafer or carrier stockers  662 ,  664  may be provided to store and buffer process and or test wafers. In other aspects, stockers  662 ,  664  may not be provided, such as where carts are directed to lithography tools directly. Another example is where indexer or wafer storage module  666  is provided on the tool set. Recirculation unit  668  may be provided to circulate and or filter air or the gas species in any given section such as tool section  612 . Recirculation unit  668  may have a gas purge, particle filters, chemical filters, temperature control, humidity control or other features to condition the gas species being processed. In a given tool section more or less circulation and or filter or conditioning units may be provided. Isolation stages  670  may be provided to isolate wafer handlers  406  and/or wafers from different processes or tool sections that cannot be cross contaminated. Locks or interconnects  672  may be provided to change wafer handler  406  orientation or direction in the event the wafer handler  406  may pick or place within a generic workspace without an orientation change. In other aspects or methods any suitable combination of process sequences or make up could be provided. 
     Referring now to  FIG.  9   , the controller  199  controls the propulsion forces, generated by the array of electromagnets  1700 , across the base  1510  so as to impart a controlled yaw moment on the base, yawing the base  1510  about a yaw axis (e.g., axis of rotation  777 ), substantially normal to the drive plane  1598 , from a first predetermined orientation relative to the frame of the chamber  118  (such as where the end effector  1520  is substantially aligned with drive line  177 ), to a second different predetermined orientation relative to the frame of the chamber  118  (such as where the end effector is extended into process module  120 ). As may be realized yawing of the base  1510  may be performed in conjunction with propulsion motion of the base  1510  (such as where a single drive line is provided in the chamber  118 ) or with the base at a predetermined location (such as where the base  1510  is rotated while remaining substantially stationary along the X and Y axes). In one aspect, referring also to  FIG.  15 C , the controller  199  controls the propulsion forces (e.g., Fx right , Fx left ), generated by the array of electromagnets  1700 , so as to impart a moment couple (illustrated in  FIG.  15 C  with movement of the substrate handler  1500  along the X axis) on the base  1510  effecting controlled yaw of the base  1510  so as to effect at least one of positioning and centering of a substrate (also referred to as a wafer payload or payload) on the base  1510  relative to a predetermined substrate holding location (such as a load lock, process module, etc.) of the frame of the chamber  118 . As may be realized, pitch (rotation about Y axis) and roll (rotation about X axis) (see  FIGS.  15 A and  15 B ) control may be effected with the controller  199  (controlling lift forces Fz across the reaction platen) simultaneously with yaw motion countering dynamic moment coupling and maintaining substantially flat yaw of the wafer holder/reaction platen in the wafer transfer plane. 
     Where a single drive line  177  is provided in each transport chamber (as illustrated in  FIGS.  1 A,  1 B,  2 ,  4 , and  5   ) or where access to a process module, such as process module  120 A (see  FIG.  8   ) from a drive line  178  closest to the process module  120 A (such as when multiple substantially parallel longitudinal drive lines  177 ,  178  are provided—see  FIG.  8   ), the controller  199  is configured to drive the base  1510  simultaneously in two or more of yaw, pitch, roll, and in propulsion (as described herein) to pick and place substrates from any suitable substrate holding stations (e.g. load locks  116 , process modules  120 , etc.). For example, the controller  199  is configured to energize the array of electromagnets  1700  as described herein so that the base moves along the drive line  177  and rotates about a base rotation axis  777  so that a substrate seating surface  1520 A of the substrate handler  1520  enters a process module  120  or other suitable holding station where the substrate S travels along a substantially straight line path  790  in a predetermined wafer/substrate transfer plane. Referring to  FIGS.  8 - 11   , in other aspects, where multiple longitudinal drive lines  177 ,  178  are provided in the transport chamber  118  the base  1510  may be rotated so that the substrate handler  1520  is aligned with a desired/predetermined substrate holding station prior to entrance into the substrate holding station. For example, the base  1510  may be positioned at an intersection between drive lines  178  and  179 A, where drive line  179  provides for extension and retraction of the substrate handler into substrate holding station  120 BH of process module  120 B (e.g., in a propulsion direction substantially orthogonal (or any suitable angle that enables access to the process module) to the propulsion direction along drive lines  177 ,  178 ). The base  1510  may be rotated about rotation axis  777  so that the substrate handler  1520  is aligned with the substrate holding station  120 BH and the base may be moved along drive line  179 A to move or extend the substrate handler  1520  into the substrate holding station  120 BH for picking/placing a substrate(s). 
     Referring to  FIGS.  14  and  14 A- 14 C , while the substrate handler  1500  has been described as including an end effector  1520 , in other aspects one or more substrate handlers may be configured as a cart  1500 C that is configured to support one or more substrates on the base  1510 . For example, the base  1510  may include one or more substrate supports  1431 - 1433  configured to stably hold a substrate (e.g., from the bottom or edge grip) so that substrate handlers  1500 ,  1500 A,  1500 B or substrate transports within, e.g., a load or other substrate holding station, may transport substrate(s) to and from the substrate supports  1431 - 1433 . In one aspect, the substrate supports  1431 - 1433  may be configured to substantially center one or more substrates on the base  1510  (i.e., the supports are self-centering supports, that are either passive supports or may be actuated (e.g., piezo-electric) from a suitable power source energized on the reaction platen) so that a center of the substrate(s) is substantially coincident with the axis of rotation  777  of the base. In some aspects, one or more of the carts  1500 C may include a substrate support rack  1440  for holding two or more substrates in a stack, where each rack level includes respective substrate supports  1431 - 1433 ,  1431 A- 1433 A. Referring to  FIGS.  14  and  14 A , the carts  1500 C may provide an interface between the substrate handlers  1500 A,  1500 B and the load locks  116  where a transport apparatus  116 R (such as a SCARA arm, linear sliding arm, etc.) of the load lock transfers substrate(s) to the cart  1500 C and the substrate handlers  1500 A,  1500 B pick the substrates from the cart and vice versa. In other aspects, where the process module  120  includes a transport apparatus  120 R (such as a SCARA arm, linear sliding arm, etc.) the carts  1500 C may be employed to transfer substrate(s) to and from the process module  120 . While the base  1510  of the carts  1500 C (and of the substrate handlers  1500 ,  1500 A,  1500 B) are illustrated as having a circular shape when viewed from the top (see  FIG.  14 C ) in other aspects, the base  1510  may have any suitable shape (e.g., square, rectangular, circular, etc. when viewed from the top) that otherwise interfaces with the array of electromagnets  1700  for effecting one or more of linear propulsion, lift, yaw, pitch, roll, and rotation control of the base  1510 . 
     Referring to  FIGS.  12 A,  12 B,  13 A,  13 B , while the transport chamber  118  has been described above as a longitudinally extended chamber that forms part of a linear processing tool, in other aspects, the transport chamber may have a cluster tool configuration. For example, referring to  FIGS.  12 A and  12 B  the transfer chamber  118 T 1  has a substantially square configuration (although in other aspects the transfer chamber may have any suitable shape such as hexagonal, octagonal, etc.). In this aspect an electrical machine  1599 R (substantially similar to the linear electrical machine  1599 ) is configured as a side-by-side transport apparatus that includes at least two side-by-side substrate handlers  1500 A,  1500 B that are substantially similar to substrate handler  1500  described herein. The array of electromagnets  1700  in this aspect is configured to move the substrate handlers  1500 A,  1500 B so that the substrate handlers  1500 A,  1500 B rotate about common axis of rotation  1277  (such axis being akin to a θ axis of, for example, a conventional SCARA type robot) for changing a direction of “extension and retraction” (the terms extension and retraction are being used herein for convenience noting that the extension and retraction is effected by linear propulsion movement of the substrate handler  1500 ,  1500 A,  1500 B along a respective drive line) of the side-by-side transport apparatus. For example, the array of electromagnets  1700  has an arrangement that forms drive lines  177 ,  178 ,  179 ,  180 . Here drive lines  177 ,  178  are spaced from one another and substantially parallel to one other so as to be substantially aligned with a respective transport openings  1180 A,  1180 F and  1180 B,  1180 E. The drive lines  179 ,  180  are substantially orthogonal to drive lines  177 ,  178  and are spaced from one another and substantially parallel to one other so as to be substantially aligned with a respective transport openings  1180 C,  1180 H and  1180 D,  1180 G. The drive lines can be in any suitable pattern (such as arced or curved segments with constant or varying radii) and orientation and the description that follows is for exemplary purposes. The electromagnets  1700 A- 1700 N (illustrated in  FIG.  12 A  but not numbered for clarity of the figure) provide for at least linear propulsion of the substrate handlers  1500 A,  1500 B through the transport openings  1180 A- 1180 H. In this aspect, the array of electromagnets  1700  also includes rotational electromagnet sub-arrays  1231 - 1234  that effect, under control of controller  199 , with the electromagnets that form the drive lines  177 - 180  the rotation of the substrate handlers  1500 A,  1500 B about the common axis of rotation  1277 . Alternatively, the electromagnets may form a dense enough and large enough grid without being specifically designated for propulsion or rotation and can perform that function based on the base&#39;s  1510  position and the control law of the controller  199 . As may be realized, while the substrate handlers  1500 A,  1500 B may rotate about the common axis of rotation  1277  at the same time, extension and retraction of the substrate handler  1500 A,  1500 B may be independent of extension and retraction of the other one of the substrate handler  1500 A,  1500 B. In general, the motion of the substrate handler  1500 A,  1500 B is independent of each other and the complexity of that motion can range from one degree of freedom to six degrees of freedom. 
     Referring to  FIG.  12 B , in one aspect, the electrical machine  1599 R includes multiple transport levels  1220 A,  1220 B that are stacked one above the other. In this aspect, each level  1220 A,  1220 B is formed by a respective level support  1221  each having a respective reference plane  1299 R that is substantially parallel with the level reference plane  1299  of the transport chamber  118 T 1  frame. Each level support  1221  includes an array of electromagnets  1700  substantially similar to that illustrated in  FIG.  12 A  for linearly driving the side-by-side substrate handlers  1500 A,  1500 B along drive lines  177 - 180  and rotating the side by side substrate handlers  1500 A,  1500 B (e.g., with full six degree of freedom control) about the common axis of rotation  1277 . Each level support  1221  is coupled to a common Z axis drive  1211  that moves the level supports  1221  and the substrate handlers  1500 A,  1500 B thereon in the Z direction so as to align the end effectors  1520  of the substrate handlers  1500 A,  1500 B on the respective level supports  1221  with a substrate transport plane  1290  of the transport openings  1180  of the transport chamber  118 T 1 . The Z axis drive  1211  may be any suitable linear actuator such as a screw drive, electromagnetic drive, pneumatic drive, hydraulic drive, etc. 
     In another aspect referring to  FIGS.  13 A and  13 B  the transfer chamber  118 T 2  has a substantially hexagonal configuration (although in other aspects the transfer chamber may have any suitable shape as noted herein). In this aspect the electrical machine  1599 R (substantially similar to the linear electrical machine  1599  of  FIG.  15 C ) is configured as a radial transport apparatus that includes a substrate handler  1500  having a double ended/sided end effector  1520 D, as will be described herein (although in other aspects a single ended/sided end effector may be employed). The array of electromagnets  1700  in this aspect is configured to rotate the substrate handler  1500  about axis of rotation  1377  (such axis being akin to a θ axis of, for example, a conventional SCARA type robot) for changing a direction of “extension and retraction” (the terms extension and retraction are being used herein for convenience noting that the extension and retraction is effected by linear propulsion movement of the substrate handler  1500  along a respective drive line), and linearly propel the substrate handler  1500  so as to extend through the transport openings  1180 A- 1180 F. For example, the array of electromagnets  1700  has an arrangement that forms radially offset drive lines  177 ,  178 ,  179 , where an angle α between adjacent drive lines depends on the number of sides/facets of the transport chamber  118 T 2  on which the transport openings  1180 A- 1180 F are located. The electromagnets  1700 A- 1700 N (illustrated in  FIG.  12 A  but not numbered for clarity of the figure) provide for at least linear propulsion of the substrate handler  1500  through the transport openings  1180 A- 1180 H and rotation of the substrate handler  1500  about axis of rotation  1377  with full six degree of freedom control so as to maintain linear transport and rotation in a desired attitude in pitch and roll. 
     Referring to  FIG.  13 B , in one aspect, the electrical machine  1599 R includes multiple transport levels  1320 A,  1320 B that are stacked one above the other in a manner substantially similar to that described above with respect to  FIG.  12 B . For example, each level  1320 A,  1320 B is formed by a respective level support  1321  each having a respective reference plane  1299 R that is substantially parallel with the level reference plane  1299  of the transport chamber  118 T 1  frame. Each level support  1321  includes an array of electromagnets  1700  substantially similar to that illustrated in  FIG.  13 A  for linearly driving (along drive lines  177 - 179 ) and rotating (about axis  1377 ) the substrate handler  1500 . Each level support  1321  is coupled to a common Z axis drive  1311  (that is substantially similar to Z-axis drive  1211 ) that moves the level supports  1321  and the substrate handler  1500  thereon in the Z direction so as to align each of the end effector  1520 D of the substrate hander  1500  on the respective level supports  1321  with a substrate transport plane  1390  of the transport openings  1180  of the transport chamber  118 T 2 . 
     Referring to  FIGS.  12 B and  13 B , the vertical motion provided by the Z actuator  1211  can be used for enabling the wafer handler  1220 A or  1220 B to perform wafer handoff operations such as pick or place to/from a wafer process station. The supports  1221 ,  1321  can include a single module (level) with the purpose of providing additional elevation capability to the wafer handler  1220 A,  1220 B to achieve larger vertical strokes during the wafer handoff operations. For example, in the case of process modules or load locks that have more than one stacked wafer slot, it would be advantageous to have a vertical lift apparatus such as Z-axis actuator  1211 ,  1311  to be able to reach each of the stacked wafer slots without increase of applied levitation power provided by the electrical machine  1599 R. 
     Referring to  FIGS.  12 A and  12 B , the vertical lift apparatus (or Z-axis actuator)  1211  and level  1221 , in another aspect, has dual (or more) separate and independently operable apparatus, e.g., one for each wafer handler  1520 . This would give the ability to perform independent vertical strokes for different wafer handlers that can access different slots on at least two independent stations (e.g., process modules, load locks, etc.). 
     Referring now to  FIGS.  15 A,  15 B,  15 C,  16 A,  16 B,  16 C, and  18   , the linear electrical machine  1599  will be described in greater detail (again noting that the electrical machine  1599 R is substantially similar to the linear electrical machine  1599 ). Generally, the linear electrical machine  1599  includes a structure (e.g., wafer handler)  1500  without magnets and any moving parts such as bearings, revolute or prismatic joints, metal bands, pulleys, steel cables or belts. As noted above, the structure or wafer handler  1500  includes the base  1510  which is formed of a paramagnetic material, diamagnetic material, or a non-magnetic conductive material. The base  1510  may have any suitable shape and size for cooperating with the electromagnets  1700 A- 1700   n  of the array of electromagnets  1700  so as to stably transport substrates S in the manner described herein. In some aspects, as will be described herein, such as where multiple wafer handlers  1500  are employed, the shape and size of the base  1510  defines a unique identification signature that identifies the wafer handler  1500  with respect to absolute position determination of the wafer handler in the manner(s) described herein. 
     In one aspect, as illustrated in  FIGS.  9  and  11 - 16 C  the base  1510  is shown with a frusto-conical shape where the tapered side  1510 TS of the frustum  1510 FR face the array of electromagnets  1700  (although other suitable shapes are operative). Here the tapered side  1510 TS of the frusto-conical shape have an angle λ (see  FIG.  15 B ) that is between about 50° and about 60° relative to the planar surfaces of the frustum  1510 FR; while in other aspects the angle λ may be greater than about 60° or less than about 50°. In other aspects, the base may have a frusto-pyramidal shape as shown in  FIGS.  8 ,  8 A, and  10   . Here each side  1510 TSP of the frustum  1510 FRP have an angle λ (see  FIG.  8 B ) that is between about 50° and about 60° relative to the planar surfaces of the frustum  1510 FRP; while in other aspects the angle λ may be greater than about 60° or less than about 50°. While the frusto-pyramidal shape is illustrated as having four sides, in other aspects the frusto-pyramidal shape may have any suitable number of sides, such as, for example, six or eight sides or may be round or have curved sides. In other aspects, the base  1510  may not have a frusto-conical or frusto-pyramidal shape and it may comprise of a planar shape with suitable and asymmetric contour and size in order to be properly controlled by electromagnets  1700 . 
     The end-effector  1520 ,  1520 D may be substantially similar to conventional end effectors; however, as described herein the end effector is rigidly coupled to the base  1510 . As an example, the end effector may be a single sided/ended (see end effector  1520 ) with a single substrate holding location  1520 A, a double sided/ended (see end effector  1520 D) with two longitudinally spaced apart substrate holding locations  1520 A,  1520 B, a side-by-side configuration where multiple substrate holding locations are arranged side-by-side (e.g., laterally spaced apart) and supported from a common base so as to extend through side-by-side substrate transport openings, a stacked configuration were multiple substrate holding locations are arranged in a stack one above the other and supported from a common base so as to extend through vertically arrayed substrate transport openings, while in other aspects the end effector may have any suitable configuration. The end effector  1520 ,  1520 D may be made of materials that can one or more of withstand high temperatures, have low mass density, have low thermal expansion, have low thermal conductivity and have low outgassing. A suitable material from which the end effector  1520 ,  1520 D may be constructed is Alumina Oxide (Al 2 O 3 ), although any suitable material may be used. 
     In one aspect, the end-effector  1520 ,  1520 D is coupled to the base  1510  with a substantially rigid and unarticulated stanchion  1510 S so as to set the end-effector  1520 ,  1520 D at a suitable nominal height H 2  relative to, for example, the level reference plane  1299 . The substrate handler  1500 , as described herein, is moved in space (in at least three degrees of freedom) using electrodynamic levitation principles. The actuation elements (e.g., the array of electromagnets  1700 ), as shown in  FIGS.  15 A- 15 C,  16 B,  16 C, and  18    include independently controlled coils or electromagnetics  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  (also referred to herein as coil segments) that generate desired magnetic field that induces thrust and lift force vectors in the base  1510 . As will be described herein, the independently controlled coils or electromagnetics  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  also effect self-deterministic absolute wafer handler position feedback for each wafer handler(s)  1500 . 
     In one or more aspects, referring also to  FIGS.  47 A,  47 B, and  47 C , the wafer handler  1500  is configured to suppress vibrations from the base  1510  excitation to the end effector  1520  that is holding a substrate or wafer S. For example, a passive vibration compensator or absorber  4700 A,  4700 B having a natural frequency mode tuned to compensate for vibration of the base  1510  under levitation propulsion forces so as to effect a substantially vibration free end effector  1520  with respect to the end effector natural vibration frequency modes. Here as described herein, the end effector  1520  is carried by the base  1510 . The excitation force on the base  1510  is a result of the alternating current induction of Eddy Currents that generates repulsive forces to maintain the base  1510  at a predetermined levitation air gap above the floor  118 L (see, e.g.,  FIGS.  44 A and  44 C ) of the transport chamber  118 . Vibration suppression is effected by the passive vibration absorber  4700 A,  4700 B of the wafer handler  1500 . The passive vibration absorber is coupled to any suitable portion of the wafer handler  1500  such one or more of the base  1510  (see  FIGS.  47 B and  48 A- 48 C ), the stanchion  1510 S (see  FIG.  47 A ), and the end effector (see  FIGS.  47 C and  48 B ). The passive vibration absorber includes a mass  4701  and a spring  4702 , where the mass  4701  is cantilevered from the spring  4702 . In other aspects, such as shown in  FIGS.  48 A- 48 C ) the mass  4701  may be suspended on/within a flexible diaphragm or membrane  4800 . The mass  4701 , the spring  4702  and the membrane  4800  are constructed of any suitable inert material, such as stainless steel. The mass  4701  may have any suitable shape and is illustrated as being spherical for exemplary purposes. Here, the resonance frequency of the passive vibration absorber  4700 A,  4700 B is tuned (e.g., via the weight of the mass and the spring stiffness) such that the base  1510  vibration is suppressed and the end effector  1520  remains substantially free of vibrations. 
     In some aspects, referring to  FIGS.  10 ,  10 A,  11 , and  11 A , multiple wafer handlers may be nested with respect to each other so as to travel linearly along the drive lines  177 - 180  as a single unit with the end effectors  1520  of the nested substrate handler disposed in a stack one above the other. For example, referring to  FIGS.  10  and  10 A  the nested bases  1510 FP (may be symmetrical as a body of revolution, revolute symmetry e.g., frusto-conical, or bi-symmetrical, e.g., frusto-pyramidal, or a channel shaped cross section of which are illustrated in  FIG.  10 A ) are configured so that one base  1510 FP may be inserted into another base  1510 FP so as to stack the bases  1510 FP in a manner similar to that of stacking cups one inside the other. The bases  1510 FP may be configured so that when stacked the vertical space between end effectors  1520  (e.g., when the end effectors  1520  are substantially level with the level reference plane  1299 ) is substantially the same as a vertical space between stacked substrate holding stations so as to provide for simultaneous picking and placing of substrates by the stacked end effectors  1520 . The stacking of the bases  1510 FP provides, in one aspect, depending on the levitation forces generated by the array of electromagnets  1700 , independent vertical or Z-axis movement of at least one of the bases  1510 FP (and the respective substrate handler  1500 A,  1500 B the base is part of). In this example, the uppermost substrate handler  1500 B may be moved in the Z-axis independent of the lowermost substrate handler  1500 A; however, when the uppermost substrate handler  1500 B is lifted away from the lowermost substrate handler  1500 A, the lowermost substrate handler  1500 A may also be moved in the Z-axis direction independent of the uppermost substrate handler  1500 B. Here, bi-symmetrical bases are interlocked and rotation of the substrate handlers  1500 A,  1500 B is linked by virtue of the shape of the bases  1510 FP so that the substrate handlers  1500 A,  1500 B rotate in unison. The stackable configuration of the bases  1510 FP provides for the stacking of any suitable number of substrate handlers one above the other (in this example two are shown stacked one above the other but in other aspects more than two substrate handlers may be stacked one above the other). 
     Referring to  FIGS.  11  and  11 A , the revolute symmetry bases  1510 FC may be stacked one above the other, moved in the propulsion direction, and moved relative to each other along the Z-axis in a manner substantially similar to that described above with respect to the frusto-pyramidal bases  1510 FP. However, in this aspect, the revolute symmetry shape of the bases  1510 FC does not interlock and provides for independent rotation of each substrate handler  1500 A,  1500 B about substrate handler axis of rotation relative to another of the substrate handlers  1500 A,  1500 B. Independent rotation of the frusto-conical based substrate handlers  1500 A,  1500 B effects a fast swapping of substrates from a single substrate holding station such as where end effector  1520  of substrate handler  1500 A is aligned with substrate holding station  120 BH for picking substrate S 1 , where end effector  1520  of substrate handler  1500 B is rotated to a position so as to not extend into the substrate holding station  120 BH. Once the substrate S 1  is removed from substrate holding station  120 BH by substrate handler  1500 A, the positions of the end effectors  1520  of the substrate handlers may be swapped so that end effector  1520  of substrate handler  1500 B is aligned with the substrate holding station  120 BH for placing substrate S 2  at the substrate holding station  120 BH while end effector  1520  of substrate handler  1500 A is rotated to a position so as to not enter the substrate holding station  120 BH. As may be realized, the substrate handlers  1500 A,  1500 B may be moved along the Z-axis to accommodate the stacked heights of the end effectors relative to a height of the substrate holding station  120 BH. Though symmetrical (revolute about one or more axis) bases have been illustrated, in other aspects one or more bases may be asymmetrical or lacking any axis of symmetry. 
     As described herein linear propulsion is generally provided by one or more linear tracks  1550  of independently controlled electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . The number of electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . Where there is more than one linear track  1550  the linear tracks  1550  are substantially parallel to each other and are spaced apart from one another depending on dimensions of the base  1510  so as to control all six degrees of freedom (roll, pitch, yaw, and translation in each of the X, Y, Z directions) of the substrate handler in space. For example, as illustrated in  FIGS.  15 B and  18   , the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  may be spaced apart from each other so that two or more electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  (cooperating so as to form a motor actuator (e.g., the motor primary)  1701  and in combination with the base (e.g., the motor secondary)  1510  the motor) of each parallel linear track  1550  are disposed underneath the base  1510  at all times in the direction of motion of the base  1510  so as to stably levitate and propel the base  1510  (as may be realized,  FIGS.  15 A,  15 B, and  18    schematically illustrate a representative configuration of the system, and are provided to show generally an exemplary representation of the interrelationship between the base  1510  and the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 , and is not intended as limiting in any way. 
     The size, numbers, and spacing (e.g., pitch) of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  in both the X and Y axes may vary, as may the size and shape of the base  1510  in relation to the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . For example, referring to  FIGS.  6  and  18   , the spacing between the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  may vary between pitch PX 1  and pitch PX 2  where the pitch PX 2  is smaller than pitch PX 1  and provides for greater definition of movement of the base  1510  and wafer handler  1500 . Here, the larger pitch (or greater distance between electromagnets) such as pitch PX 1  is employed for long movements of the wafer handler  1500  where position location of the wafer handler  1500  is to be grossly known. In areas where picking and placing of substrates S occurs (or other areas where wafer handler position is to be known with increased position definition/accuracy), such as at the process module  120 , the spacing or pitch PX 2  between the electromagnets is decreased to provide a higher electromagnet density that effects greater definition of position location of the wafer handler  1500  (compared to the definition of position location provided by electromagnets spaced apart by the larger pitch PX 1 ) so that the wafer handler  1500  picks and places substrates S at the process module  120  with sub-micron position accuracy. In the examples illustrated the pitch PX of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  is shown as varying in the X direction along the longitudinal length of the transport chamber  118  to provide varying degrees of wafer handler position accuracy; however, the pitch of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  may also vary in the Y direction (see pitches PX 3  and PX 4 ) along a lateral width of the transport chamber  118  so as to provide increased accuracy with respect to wafer handler  1500  rotations and/or Z axis height movements. For example, in the areas where picking and placing of substrates S occurs (or other areas where wafer handler position is to be known with increased position definition/accuracy) the pitch between electromagnets may be a decreased pitch PX 3  compared to a pitch between the electromagnets in the areas of long motions (e.g., motions between substrate holding stations) where wafer handler rotations and Z height motions are not desired. 
     In one aspect, as illustrated in  FIGS.  8  and  18   , the array of electromagnets  1700  may also include stabilization tracks  1550 S disposed laterally outward of the tracks  1550 . In  FIG.  18    the stabilization tracks  1550 S may be formed by one or more rows of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . The stabilization tracks may be substantially similar to the tracks  1550  and are configured to provide additional stabilization of the base  1510  through the generation of additional lift and/or propulsion forces (e.g., in addition to the lift and propulsion forces generated by electromagnets of the parallel linear tracks  1550 ) that act on the base  1510 . The result is a substrate handler  1500  that can move along a direction of the tracks  1550  (i.e., the propulsion direction) while changing orientation in one or more of roll, pitch and yaw. According to magnetic induction principles where the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are akin to the “primary” and the base  1510  corresponds to the “secondary” where electrical currents are induced by means of Eddy current effects. 
       FIGS.  17  and  20    illustrate an actuator control system network  1799  (which may be part of or communicably coupled to controller  199 ), in accordance with an aspect of the disclosed embodiment, configured to effect individual control of each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  to provide the desired force components and degrees of freedom described and illustrated with respect to  FIGS.  15 A- 16 C . In one aspect, the actuator control system is configured so that the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  form motor actuator units (collectively referred to as the motor actuator), each motor actuator unit having m number of electromagnets/coils cooperating to form the motor (where m is a dynamically selectable number of two or more electromagnets forming one or more of the motor actuator units as will be described further below). The actuator control system network  1799  is thus a scalable motion control system that has a clustered architecture with at least a master controller  1760  and distributed local drive controllers  1750 A- 1750   n  as will be described in greater detail below. In this aspect, groups of electromagnets  1700 G 1 - 1700 Gn are coupled to a respective local drive controller  1750 A- 1750   n  that is configured to control the electrical currents on electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  within the respective group of electromagnets  1700 G 1 - 1700 Gn. The local drive controller  1750 A- 1750   n  can be a “slave” in a network that is connected to a master controller  1760  that is configured to specify the desired forces (e.g., thrust and lift) for each individual electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  to effect the desired motion of the wafer handler  1500  in space. The drive controllers  1750 A- 1750   n , illustrated generally as drive controller  1750  in  FIG.  20    (where  FIG.  20    illustrates a drive controller and its respective group of electromagnets  1700 G 1 - 1700 Gn) are coupled to the respective electromagnets  1700 A- 1700   n  by an amplifier drive circuit  2010  as will be described herein. 
     As will also be described herein, the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  can be physical electromagnets/coils that can be dynamically configured when it comes to the respective “phase” definitions of each coil with respect to “phase” definitions of the other electromagnets/coils of the given motor actuator unit so that the position of the given motor actuator unit (formed of cooperative excitation phases of the motor under propulsion) may be deemed as moving virtually in unison with the base propulsion, though the physical electromagnets/coils are fixed (e.g., static) as will be described further below. This provides continuity in the desired force vectors for motion control of the substrate handler. 
     In accordance with aspects of the disclosed embodiment, and referring to  FIGS.  18  and  19   , the controller  199  is operably coupled to the array of electromagnets  1700  and the alternating current power source  1585  and configured to sequentially excite the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  with multiphase alternating current with a predetermined excitation characteristic (such as, e.g., inductance, a phase lag/amplitude, and/or power factor as will be described herein—see also  FIGS.  23  and  25 A ) so that each reaction platen or base  1510  (of the wafer handler  1500  or cart  1500 C) is levitated and propelled with up to six degrees of freedom. Here, as will be described in greater detail herein, the controller  199  is configured so as to determine reaction platen position feedback, in at least one degree of freedom from the up to six degrees of freedom, from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  effecting levitation or propulsion of the base  1510 . The variance in the predetermined excitation characteristic defines self-deterministic reaction platen position feedback of each of the at least one electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 , of the array of electromagnets  1700 , effecting levitation or propulsion of the base  1510 . 
     As described herein, the array of electromagnets  1700  includes electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  configured to produce levitation and propulsion forces that drive, under control of controller  199 , the wafer handler  1500  along a predetermined trajectory through the transport chamber  118 . To drive the wafer handler  1500  along the predetermined trajectory the controller  199  is configured to determine a real time spatial position (e.g., in one or more of the up to six degrees of freedom X, Y, Z, Rx, Ry, Rz) of the wafer handler  1500 . Here absolute position feedback of the wafer handler  1500  is determined by the controller  199  (or any other suitable controller such as included in the actuator control system network  1799 ) based on the effects of magnetic induction on the interaction between the base  1510  of the wafer handler  1500  (or cart  1500 C) and each electromagnet (e.g., actuator)  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . For example, as can be seen in  FIG.  19   , the base  1510  and each electromagnet create a magnetic circuit  1910  (only electromagnet  1700 A is shown in  FIG.  19    for illustrative purposes only and a similar circuit is formed with the other electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  when the base  1510  passes over and is driven by the other electromagnets) that effects the levitation and propulsion of the base  1510  by the electromagnet  1700 A. Each electromagnet  1700 A (again noting electromagnet  1700 A is used for exemplary purposes only and that the other electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are substantially similar) has a resistance R and an inductance L. An input voltage V of the electromagnet  1700 A is, as described herein, a multiphase alternating current voltage with a predetermined amplitude and frequency that is applied to a predetermined electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  for driving the base  1510  as described herein, where the predetermined electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  has a known location within the transport chamber  118 . As may be realized, the resulting current I through electromagnet  1700 A is determined by a dynamic response of the circuit  1910  to the input voltage. For a given input voltage V at a given time t, the respective current I in the electromagnet  1700 A can be determined with the following equation: 
         V ( t )= R I ( t )+ L dI ( t )/ dt   [eq. 1]
 
     where, R is the resistance of the electromagnet  1700 A and L is the inductance of the electromagnet  1700 A. 
     Referring also to  FIG.  20   , each of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the array of electromagnets  1700  is communicably coupled to an amplifier driver circuit  2010 . The amplifier driver circuit  2010  includes a field-effect transistor  2011  and is configured to provide feedback of the respective electric current I flowing through a respective electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . 
     As, may be realized, the current I flowing through the electromagnet  1700 A lags (in time) the input voltage V (e.g., phase lag). The phase lag can be expressed in the voltage drop across the inductor L of the electromagnet  1700 A as: 
         dI ( t )/ dt   [eq. 2]
 
     Referring to  FIGS.  18 ,  19 , and  21 A- 21 C , the amount of phase lag (e.g., between the excitation voltage V and the current I of the electromagnet  1700 A) depends on the resistance R and the inductance L of the magnetic circuit  1910 . An electric circuit representation of the electromagnet  1700 A is illustrated in  FIG.  21 A  with the electromagnet  1700 A under an alternating input voltage excitation without the base disposed adjacent the electromagnet  1700 A (i.e., the left side of  FIG.  21 A ) and with the base  1510  disposed adjacent the electromagnet  1700 A (i.e., the right side of  FIG.  21 A ). It is noted that the base  1510  is disposed above the electromagnet  1700 A with a predetermined air gap distance for exemplary purposes but in other aspects the base  1510  may be magnetically suspended by the electromagnets in any suitable manner. Here, the alternating current voltage V generates a respective alternating current I with a lagged response (e.g., lagged behind the voltage V in time) as a function of the inductance L of the electromagnet  1700 A. The periodic voltage V(t) through the electromagnet  1700 A can be expressed as follows: 
         V ( t )= V   0  sin(ω t )  [eq. 3]
 
     where V 0  is the voltage amplitude and G is the angular frequency. The periodic current I(t) can be expressed as follows without the presence of the base  1510  adjacent the electromagnet  1700 A: 
         I 1( t )= I   0 1 sin(ω t+ϕ 1)  [eq. 4]
 
     and as follows with the base  1510  present adjacent the electromagnet  1700 : 
         I 2( t )= I   0 2 sin(ω t+ϕ 2)  [eq. 5]
 
     where I 0  is the current amplitude and ϕ1 and ϕ1 are the respective magnetic fluxes. As may be realized, the current I responses between the electric circuit on the left side of  FIG.  21 A  (e.g., without the base  1510  adjacent the electromagnet  1700 A) and the electric circuit on the right side of  FIG.  21 A  (e.g., with the base  1510  adjacent the electromagnet  1700 A) are substantially different because the inductance L is affected by the presence of the base  1510  due to the induction of Eddy currents that impact the magnetic field generated by the electromagnet  1700 A. 
     Referring to  FIGS.  17  and  20   , the local controller  1750 ,  1750 A- 1750   n  commands excitation of the electromagnet  1700 A with an input voltage V and is configured to determine the resultant electromagnet current I in any suitable manner (such as by being programmed to execute equations 4 and 5 above or by being configured to measure the current in the electromagnet  1700 A in any suitable manner). Knowing the input voltage V and the resultant electromagnet current I the local controller  1750 ,  1750 A- 1750   n  determines the phase lag between the voltage V and current I; and based on the phase lag the local controller  1750  determines if the base  1510  or any portion thereof is located adjacent the electromagnet  1700 A. Here, the amount of phase lag is employed to quantify the relative position of the base  1510  with each of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . 
       FIG.  21 B  is an exemplary illustration of the base at different locations X 1 -X 4  relative to, e.g., electromagnet  1700 A along a unidimensional path  2110  (although in other aspects the path may be multidimensional). An equation representing the current I 1 ( t ),  12 ( t ),  13 ( t ),  14 ( t ) for each respective location 1-X 4  is provided in  FIG.  21 B . For exemplary purposes the input voltage V may be considered substantially constant. As the base  1510  moves relative to the electromagnet  1700 A, the respective current I response changes at least in phase (and may also change in amplitude). Based on the change in phase of the current I, the measured current I response and the given input voltage V are correlated with the position X 1 -X 4  of the base  1510  along the path  2110 . For example, the correlation of the measured current I response and the given input voltage V with the position X 1 -X 4  of the base  1510  may be expressed in terms of a change in the mutual inductance L of the electromagnet  1700 A. The mutual inductance L between the electromagnet  1700 A and the base  1710  can be expressed as follows: 
     
       
         
           
             
               
                 
                   
                     L 
                     ⁡ 
                     ( 
                     x 
                     ) 
                   
                   = 
                   
                     
                       L 
                       s 
                     
                     + 
                     
                       
                         1 
                         
                           I 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           ∫ 
                           
                             - 
                             a 
                           
                           a 
                         
                         
                           dx 
                           ⁢ 
                           
                             
                               ∫ 
                               
                                 - 
                                 b 
                               
                               b 
                             
                             
                               
                                 
                                   dyB 
                                   c 
                                 
                                 ( 
                                 
                                   x 
                                   , 
                                   y 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 T 
                                 ⁡ 
                                 ( 
                                 
                                   x 
                                   , 
                                   y 
                                 
                                 ) 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     6 
                   
                   ] 
                 
               
             
           
         
       
     
     Where L s  is the electromagnet self-inductance, I is the electromagnet current, a is the base  1510  half-length, b is the base  1510  half-width, x and y are the base  1510  location in space, B c  is the magnetic flux density at the electromagnet, and T(x, y) is a linear combination of basic functions. 
     With reference to  FIG.  21 B , the relationship between the mutual inductance L and the position X of the base  1510  is illustrated in  FIG.  21 C . It is noted that the location X=3 in  FIG.  21 B  (with the base  1510  located substantially directly over or fully covers the electromagnet  1700 A) is illustrated as location X=0 in  FIG.  21 C . As the location of the base  1510  changes from X 3  to X 1  (the base is moving along path  2111  in  FIG.  21 B ) the base  1510  moves out of alignment with the electromagnet  1700 A causing the mutual inductance L to increase. The mutual inductance L reaches a maximum value when the base  1510  completely clears the electromagnet  1700 A, such as when the base is at location X 1  (see  FIG.  21 B ) relative to the electromagnet  1700 A. 
     As described above, inductance is utilized to identify the location of the base  1510  in space for exemplary purposes only. Referring also to  FIGS.  19 ,  49 A and  49 B , any suitable variables may be employed to identify the location of the base  1510  in space. For example, the circuit  1910  in  FIG.  19    has an inherent characteristic that may be leveraged to provide a self-deterministic position feedback solution of the reaction platen. Here, the relationship between the voltage and the current may be out of phase due to the reactive load caused by the inductor (coil). The power (e.g., apparent power) to drive current through the coil  4500 C is higher than the power (e.g., the real power) dissipated through the coil  4500 C itself as illustrated in  FIG.  49 A . The apparent power is supplied by the power supply (such as current amplification power supply units  3011  or any other suitable power supply) to drive a predetermined alternating current through the coil  4500 C. The real power shown in  FIG.  49 A  is dissipated through the coil resistance and the reactive power is the load resulting from the inductive reactance of the coil  4500 C. 
     The relationship between the coil resistance and the inductive reactance is illustrated in  FIG.  49 B . The impedance Z is the equivalent load on the power supply (such as current amplification power supply units  3011  or any other suitable power supply). The angle Φ is the phase difference between the coil AC voltage and the respective AC current. Where the impedance reactance is larger than the coil resistance, the angle Φ may be close to or approached about 90° in which case substantially no current passes through the coil  4500 C, resulting in a lack of levitation of the base  1510 . The measure of such efficiency is called the power factor (PF), which is defined as the cosine of the angle Φ (i.e.PF=cos Φ). 
     To maximize the levitation efficiency, the power factor is maximized to be or approaches about 1 (e.g., as close to 1 as possible), where the angle Φ is (or approaches) zero. To maximize the power factor, a capacitor CAP may be added in series with the coil  4500 C. The capacitor CAP has a reactance effect that may negate the inductive reactance imposed by the coil  4500 C. The reactance of each of the capacitor CAP and coil  4500 C is a function of the AC frequency imposed by the voltage. Here reactance of the capacitor CAP is substantially the same in magnitude as the respective inductive reactance of the coil  4500 C to maximize the levitation efficiency of the base  1510 . The relationship between the inductive reactance X L  and capacitance reactance X C  is as follows: 
     
       
         
           
             
               
                 
                   
                     X 
                     L 
                   
                   = 
                   
                     2 
                     ⁢ 
                     π 
                     ⁢ 
                     FL 
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     7 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     X 
                     C 
                   
                   = 
                   
                     1 
                     
                       2 
                       ⁢ 
                       π 
                       ⁢ 
                       FC 
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     8 
                   
                   ] 
                 
               
             
           
         
       
     
     noting that F is the frequency and due to capacitance selection X C =X L , where 
     
       
         
           
             
               
                 
                   
                     2 
                     ⁢ 
                     π 
                     ⁢ 
                     FL 
                   
                   = 
                   
                     1 
                     
                       2 
                       ⁢ 
                       π 
                       ⁢ 
                       FC 
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     9 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     and 
                     ⁢ 
                         
                     C 
                   
                   = 
                   
                     1 
                     
                       4 
                       ⁢ 
                       
                         π 
                         4 
                       
                       ⁢ 
                       FL 
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     10 
                   
                   ] 
                 
               
             
           
         
       
     
     where C is the selected capacitance. As described herein, the power factor (PF) of each coil  4500 C may be used to identify the absolute position of the base  1510 . Another example of a coil variable that may be employed for absolute position decoding of the base  1510  is the coil impedance Z (see  FIG.  49 B ) where the impedance can be determined as the RMS (root mean square) ratios of the of the AC voltage and AC current at each respective coil  4500 C, where 
     
       
         
           
             
               
                 
                   Z 
                   = 
                   
                     
                       RMS 
                       ⁡ 
                       ( 
                       V 
                       ) 
                     
                     
                       RMS 
                       ⁡ 
                       ( 
                       I 
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     11 
                   
                   ] 
                 
               
             
           
         
       
     
     As can be seen above, the coil  4500 C variables inductance I, power factor PF, and impedance Z are examples of metrics (e.g., excitation characteristics) that determine the position of the base  1510  and define the self-deterministic reaction platen or base  1510  pose feedback. Other metrics may also be used such as those defined by machine learning and data analytics techniques, such as the neural network  199 N. 
     Still referring to  FIGS.  21 A- 21 C , the aspects of the disclosed embodiment employ the array of electromagnets  1700  to magnetically levitate the wafer handler  1500  with electromagnetic induction. As described herein, the aspects of the disclosed embodiment separate the array of electromagnets  1700  from the wafer handler  1500  with a non-magnetic isolation wall (such as the floor  118 L of the transport chamber  118 , or where the array of electromagnets  1700  are located on lateral sides of the transport chamber  118  the side walls form the non-magnetic isolation wall). Examples of suitable materials from which the non-magnetic isolation wall is constructed include, but are not limited to, the 300-series stainless steel (as described herein), the low conductivity aluminum such as an 6061 series aluminum (as described herein), or any other suitable non-magnetic material). Here, the non-magnetic isolation wall facilitates the induction of Eddy currents on the base  1510  (located within the sealed environment of the transport chamber  118 ) from the alternating magnetic field generated by the array of electromagnets  1700 . The voltage V applied to the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  and the respective currents I are employed by the local controllers  1750 A- 1750   n  (or the controller  199 ) to determine the absolute position of the wafer handler  1700  in a reference frame (X, Y, Z—see, e.g.,  FIG.  1 A ) of the transport chamber  118  without employing additional sensing technology (e.g., dedicated position sensors) that increase both the size and cost of the transport chamber  118 . As described herein, and also referring to  FIG.  20   , the local controllers  1750  are coupled to the respective electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  by the amplifier drive circuit  2010 . This amplifier drive circuit includes a current sensor (such as in the field-effect transistor  2011 ) that effects measurement of the current I in the respective electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . Accordingly, the voltage V and the current I are known and the local controllers  1750 A- 1750   n  (or controller  199 ) can effect absolute position determination of the wafer handler  1500  as described herein without integration of dedicated position sensors, associated hardware, and controls in (or on) the transport chamber  118 . Here, the aspects of the disclosed embodiment support absolute position detection of the wafer handler  1500  over long motions of the wafer handler  1500  within a linear tool (or cluster tool) with the cost savings obtained from exclusion of dedicated wafer handler position sensors. 
     Referring to  FIG.  28   , as well as  FIGS.  22 - 24   , the local controllers  1750 A- 1750   n  (or the controller  199 , such as where the local controller conveys the voltage V and current I to the controller  199  for position determination) are configured with any suitable strategy for position determination of the wafer handler  1500  within the transport chamber  118 . As an exemplary position determination strategy, the controller  199  or controllers  1750 A- 1750   n  include a finite element model (FEA) configured to provide a matrix of coil inductances based on the position of the wafer handler  1510  within the transport chamber  118 . Here, a multidimensional table (referred to as a forward position-inductance table and represented as FEA model  2810  in  FIG.  28   ) is generated that relates each wafer handler  1510  spatial position in the array of electromagnets  1700  to the respective inductances of the electromagnets in the array of electromagnets  1700 . The respective inductances of the electromagnets in the array of electromagnets  1700  may be referred to as a coil inductance matrix that is associated with a given six degree of freedom position of the base  1510  of the wafer handler  1500 . An inverse position inductance table (represented in  FIG.  28    as inverse FEA model  2820 ) is generated from the forward position-inductance table  2810 . The inverse position inductance table  2820  is configured to effect determination of the wafer handler  1500  position based on the coil induction matrix. As described above, other variables or their combinations can be employed in addition to the coil inductance, such as the power factor PF and impedance Z. 
     To determine the position of the wafer handler  1500  in the transport chamber  118 , the controller  199  (or local controllers  1750 A- 1750   n ) includes an inductance estimator  2830  configured to estimate the real time inductances of the elements of the coil induction matrix based on the voltages and currents of the electromagnets in the array of electromagnets  1700 . The inductance estimator  2830  is configured to estimate the real time inductances L of the electromagnets in the array of electromagnets  1700  based on the alternating current voltages V and currents I (as determined/measured by the amplifier drive circuit as described herein). As an example, to determine the real time inductances L, the voltage V and current I in each electromagnet in the array of electromagnets  1700  can be expressed as in equation 1 above; however, it may be more practical to express the relationship between the voltage V and current I in terms of the Root-Mean-Square (RMS) values of the voltage V and current I flowing through any given electromagnet in the array of electromagnets  1700  as follows: 
         V   RMS   =Z I   RMS   [eq. 12]
 
     where V RMS  is the RMS of the alternating current voltage at the electromagnet terminals imposed by the local controller  1750 ,  1750 A- 1750   n ; IMs is the RMS of the alternating current measured by the local controller  1750 ,  1750 A- 1750   n  (such as by the amplifier drive circuit  2010 —see  FIG.  20   ) at the respective electromagnet; Z is the electromagnet impedance in ohms; R is the resistance of the electromagnet in ohms; X L  is equal to 2πfL and is the inductive reactance of the electromagnet in ohms; f is the frequency of the alternating current signals in Hertz; and L is the inductance of the electromagnet. Accordingly, the inductance of any given electromagnet can be measured or estimated as: 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       
                         [ 
                         
                           
                             
                               ( 
                               
                                 
                                   V 
                                   RMS 
                                 
                                 
                                   I 
                                   RMS 
                                 
                               
                               ) 
                             
                             2 
                           
                           - 
                           
                             R 
                             2 
                           
                         
                         ] 
                       
                     
                     
                       2 
                       ⁢ 
                       π 
                       ⁢ 
                       f 
                     
                   
                 
               
               
                 
                   [ 
                   
                     eq 
                     . 
                         
                     13 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring still to  FIGS.  22 - 24   , as described herein the aspects of the disclosed embodiment may be employed to locate the position of multiple wafer handlers  1500 A,  1500 B in the same or common transport chamber  118 . As described with respect to  FIGS.  17  and  20    herein, each local controller  1750 A- 1750   n  is communicably coupled to a respective group  1700 G 1 - 1700 Gn (only a portion of each group is illustrated in the Figs.) of electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   nl ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  in the array of electromagnets  1700 . The locations of each of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are known relative to the reference frame REF (X, Y, Z) of the transport chamber  118  (or of the processing tool to which the transport chamber  118  is a part). As noted herein, the local controllers  1750 A- 1750   n  are communicably coupled to (master/central) controller  199  in any suitable manner (e.g. wired connection or wireless connection), where the controller  199  (or the master distributed controller  1760 ) is configured to monitor and control the condition (e.g., energization state) of each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the array of electromagnets  1700 . 
     As an example, the controller  199  (or master distributed controller  1760 ) defines the alternating current voltage V excitation for the electromagnets of the array of electromagnets  1700  while requesting, from the local controllers  1750 A- 1750   n , the voltage-current phase measurements from each electromagnet of the array of electromagnets  1700 . The controller  199  determines from the voltage-current phase measurements the position of the base  1510  of the wafer handler  1500  within the transport chamber  118  in the manner described above as well as determines control commands to effect a desired level of levitation and propulsion of the wafer handler  1500  along a predetermined trajectory. Here, the local controller  1750 A- 1750   n  substantially continuously measure at least the voltage-current phase, and in some aspects the amplitude ratio, of the respective electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . The measured voltage-current phase, and in some aspects the amplitude ratio are transmitted from the local controllers  1750 A- 1750   n  to the controller  199  so that the controller  199  builds a feedback matrix that can be input into a matrix transformation whose output can be the six degrees of freedom spatial position of the wafer handler  1500  within the transport chamber  118 . 
     As noted herein, the base  1510  of each wafer handler  1500  may have a unique size and shape that effects a unique electromagnet measurement matrix for a given unique position within the transport chamber  118  relative to the entire array of electromagnets  1700 . For example, the base  1510  of the wafer handler  1500 A may have one fiducial  2210  while the base  1510  of the wafer handler  1500 B has two fiducials  2210 A,  2210 B. The different number of fiducials (and the locations of the fiducials) provide for unique identification of each wafer handler  1500 A,  1500 B along, for example, the drive plane  1598  (see at least  FIGS.  15 A and  16 B ) as well as for a respective yaw angle orientation relative to the array of electromagnets  1700 , based on the phase lag of each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  interacting with the base  1510 . Here, to effect the unique identification of each wafer handler  1500 A,  1500 B the base  1510  overlaps a suitable number of electromagnets such that a unique pattern of electromagnet measurements (e.g., voltage and/or current magnitude and/or phases) is obtained for each wafer handler  1500 A,  1500 B and associated with the unique position of the respective wafer handler  1500 A,  1500 B. For exemplary purposes only, at least six electromagnets sense the position of the base  1510  so as to provide a predetermined overlap with the base  1510  so as to unique identify the base  1510  and to provide motion continuity along the (multidimensional) drive plane  1598  (see at least  FIGS.  15 A and  16 B ). It should be understood that in other aspects, more or less than six electromagnets sense the position of the base  1510  so as to provide a predetermined overlap with the base  1510  and to provide motion continuity along the (multidimensional) drive plane  1598 . 
     Still referring to  FIGS.  22 - 24    and also to  FIG.  28   , the transformation of the measured phase lag (and in some aspects the amplitude) of each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  to the position of the wafer handler  1500  may be effected by a machine learning algorithm such as a neural network that is designed and trained with any suitable machine learning techniques. For example, as described herein, the mutual inductance for each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  can be measured as described herein. The neural network  199 N is trained to uniquely correlate the coil inductance matrix (see  FIG.  28   ) with the position of the wafer handler  1500  within the transport chamber  118 .  FIG.  24    is an exemplary illustration of the implementation of the neural network to transform the coil inductance matrix (which may include a coil magnitude matrix and coil phase matrix) to the position of the wafer handler  1500 . 
     Referring to  FIG.  23   , in addition to or in lieu of employment of the phase lag to effect position determination of the wafer handler  1500 ,  1500 A,  1500 B, a power factor for each electromagnet in the array of electromagnets  1700  may be employed for position determination of the wafer handler  1500 ,  1500 A,  1500 B. The power factor is a measure of efficiency of an inductive load in alternating current circuits, such as the circuit created between the electromagnets in the array of electromagnets  1700  and the base  1510  of the wafer handler  1500 A&lt; 1500 B. As described herein, as the base  1510  approaches an electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 , the respective inductance L of that electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  changes as a result of, e.g., the induction of Eddy currents on the base  1510 . The change in the electromagnet inductance L effects a change in the associated reactance and the resultant overall impedance of the circuit formed between the electromagnet and the base  1510 . This change in impedance directly affects the respective power factor (or efficiency) associated with the electromagnet. 
     In the aspect illustrated in  FIG.  23   , the controller  199  is configured to monitor at least the power factors of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  in the array of electromagnets  1700  to generate a real time power factor matrix that represents a spatial efficiency of the entire array of electromagnets  1700 . As above, the shape/size of the base  1510  of each wafer handler  1500 A,  1500 B provides for uniquely identifying (e.g., through a respective unique power factor signature, e.g., a unique electromagnet power factor pattern) the location of the wafer handler  1500 A,  1500 B relative to the array of electromagnets  1700  within the transport chamber  118 . As can be seen in  FIG.  23   , each electromagnet in the array of electromagnets has a power factor where a respective matrix of power factors (e.g., a respective power factor matrix) is employed by the controller  199  as an input to a position decoding algorithm (e.g., of the controller  199 , such as the neural network described herein) to determine the location of the wafer handler(s)  1500 A,  1500 A in a manner similar to that described above, where the variance in a power factor of any given electromagnet of the array of electromagnets is indicative of a proximity of the base  1510  relative to the given electromagnet. For exemplary purposes only, as can be seen in  FIG.  23   , the power factor matrix for wafer handler  1500 A includes the power factors (e.g., CXX where XX is the identity of an electromagnet where as a non-limiting example, C 22  is the power factor for electromagnet  22 ) C 22 -C 25 , C 31 -C 36 , C 41 -C 45 , and C 52 -C 55  corresponding to electromagnets  22 - 25 ,  31 - 36 ,  42 - 45 , and  52 - 55  of the array of electromagnets  1700  interacting with the base  1510  of wafer handler  1500 A. The power factor matrix for wafer handler  1500 B includes the power factors C 63 -C 67 , C 73 -C 77 , C 83 -C 87 , and C 93 -C 97  corresponding to electromagnets  63 - 67 ,  73 - 77 ,  83 - 87 , and  93 - 97  of the array of electromagnets  1700  interacting with the base  1510  of wafer handler  1500 B. In a manner similar to that noted above, the neural network  199 N is trained to correlate the power factors for the electromagnets of the array of electromagnets  1700  with a position of the respective wafer handler  1500 A,  1500 B relative to the array of electromagnets so as to determine the absolute position of the respective wafer handler  1500 A,  1500 B within the transport chamber  118 . 
     Referring to  FIGS.  22  and  25   , in accordance with the aspects of the disclosed embodiment, the predetermined excitation characteristic (such as, e.g., inductance, phase lag/amplitude, and/or power factor as described herein) may be obtained by the controller from a unique and substantially constant alternating current frequency that does not match a fundamental alternating current frequency that effects generation of the levitation and propulsion forces of the array of electromagnets  1700 . For exemplary purposes only, the electromagnets of the array of electromagnets  1700  operate at a substantially fixed alternating current frequency of about 80 Hz to effect levitation and propulsion of the wafer handler  1500 A,  1500 B. The controller  199  is in one or more aspects configured to determine the position/location of the wafer handlers  1500 A,  1500 B based on one or more of the inductance, phase lag/amplitude, and/or power factor as determined with the alternating current voltage and alternating current at the about 80 Hz frequency; while in other aspects, the controller effects superimposing of a second frequency (such as for example a voltage and current at about 1 KHz) to the fundamental frequency of about 80 Hz as illustrated in  FIG.  25   , where the controller  199  is configured to determine the position/location of the wafer handlers  1500 A,  1500 B based on one or more of the inductance, phase lag/amplitude, and/or power factor as determined with the alternating current voltage and alternating current at the about 1 KHz frequency; while in still other aspects the controller  199  is configured to determine the position/location of the wafer handlers  1500 A,  1500 B based on one or more of the inductance, phase lag/amplitude, and/or power factor as determined with the alternating current voltage and alternating current at both the about 80 Hz frequency and the about 1 KHz frequency (e.g., where determinations made at one of the frequencies is used to verify determinations made at another of the frequencies). The second frequency is separate and distinct from the fundamental frequency so as to decouple position feedback determination from levitation and propulsion of at least one base  1510  (also referred to as a reaction platen) as described herein. 
     As can be seen in  FIG.  25   , exemplary power factor determinations are provided for both the about 80 Hz frequency and the about 1 KHz frequency. Here, the power factor (PF 1 ) at the about 80 Hz frequency is expressed as: 
       PF 1 =cos(ϕ 1 )  [eq. 14]
 
     and the power factor (PF 2 ) at the about 1 KHz frequency is expressed as: 
       PF 2 =cos(ϕ 2 )  [eq. 15]
 
     where ϕ 1  and ϕ 2  are the phase lag for the about 80 Hz and the about 1 KHz frequencies respectively. It is noted that any suitable frequencies may be employed for levitation/propulsion of the wafer handler  1500 A,  1500 B and position determinations of the wafer handler  1500 A,  1500 B. The superimposing of the second frequency on the fundamental frequency for position determination/feedback of the wafer handler  1500 A,  1500 B decouples the position determination/feedback from the fundamental frequency (i.e., decouples position determination/feedback from levitation and propulsion). The position determination frequency (e.g., the superimposed frequency) may be chosen to be a frequency that is high enough such that the frequency provides for position feedback determination (e.g., via determination of the power factor, inductance, and/or phase lag/amplitude) with a smaller latency/delay compared to that of the fundamental frequency. Using the examples of an about 80 Hz fundamental frequency and an about 1 KHz second frequency the power factor calculation (see equations 9 and 10 above) latency would be about 0.0125 sec (e.g., 1/80 Hz) and 0.001 sec ( 1/1000 Hz) respectively. 
     Referring to  FIGS.  26  and  27   , an experimental data set is provided and illustrates a dependency between the position of the base  1510  of the wafer handler  1500  and the respective power factors of the electromagnets in the array of electromagnets  1700 . Here, the electromagnets are identified as M 1 C 0 -M 1 C 2 , M 2 C 0 -M 2 C 2 , and M 3 C 0 -M 3 C 2  but are otherwise substantially similar to the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  described herein. Also, the array of electromagnets  1700  is illustrated as having nine electromagnets for exemplary purposes only and may have more (or less) than nine electromagnets. As can be seen in  FIGS.  26  and  27   , at each X position of the base  1510 , there is a unique set of power factors that uniquely correlate with the X position of the base  1510 . For example, as the base  1510  moves towards the positive X direction indicated in  FIG.  26   , the front (or leading) row of power factors (e.g., corresponding to electromagnets M 1 C 0 -M 1 C 2  in the X position illustrated in  FIG.  26   ) decrease while the rear (or trailing) row of power factors (e.g., corresponding to electromagnets M 3 C 0 -M 3 C 2  in the X position illustrated in  FIG.  26   ) increase. The decrease in the leading row of power factors and the increase in the trailing row power factors occurs based on changes in the electromagnet M 1 C 0 -M 1 C 2 , M 3 C 0 -M 3 C 2  that result from the changes in the magnetic circuit that, where the changes in the magnetic circuit are effected by the presence and position of the base  1510 . The controller  199  (or one or more of controllers  1750 ,  1750 A- 1750   n ,  1760 ) is configured to determine/decode the location of the base  1510  (and of the wafer handler  1500 ) along the X axis based on the vector of power factors from the electromagnets in the array of electromagnets  1700 . As may be realized, vectors of power factors may also be employed for determination of the base  1510  (and wafer handler  1500 ) location along the Y axis in addition to or in lieu of the determining the location along the X axis (e., such as where the array of electromagnets  1700  provides for multidimensional X-Y movement of the base  1510 ). 
     In a manner similar to that described herein, the controller  199  (or one or more of controllers  1750 ,  1750 A- 1750   n ,  1760 ) is configured to determine the Z position (e.g., amount of levitation or lift) of the base  1510  (and the wafer handler  1500 ) based on the changes in inductance, a phase lag/amplitude, and/or power factor. For example, the values for the inductance, a phase lag/amplitude, and/or power factor are known the controller with the base  1510  travelling along the drive plane. As the lift of the base  1510  increases (the distance between the base  1510  and the electromagnets in the Z direction increases) the affect the base  1510  has on the inductance, a phase lag/amplitude, and/or power factor may decrease. Likewise, as the lift of the base  1510  decreases (the distance between the base  1510  and the electromagnets in the Z direction decreases) the affect the base  1510  has on the inductance, a phase lag/amplitude, and/or power factor may increase. 
     In the aspects of the disclosed embodiment, the controller  199  is configured, in a manner similar to that described herein, to correlate the increase or decrease in the inductance, a phase lag/amplitude, and/or power factor with the Z position of the base  1510  (and the wafer handler  1500 ) so as to determine the Z position of the base  1510  in the Z direction. In a manner similar to that described herein, as the base  1510  moves further away in the Z direction from any given electromagnet the power factor of the given electromagnet increases, and the closer the base  1510  moves in the Z direction towards the given electromagnet the power factor of the given electromagnet decreases. These changes in the power factor with respect to the movement of the base  1510  towards and away from the electromagnets in the array of electromagnets may be correlated with the height of the base  1510  above the drive plane  1598  in the controller  199  (and/or other controllers described herein) in a manner similar to that described above with respect to movement of the base  1510  along the X (or Y) axis. With reference to  FIG.  18   , it is noted that the electromagnets between the edges of the base  1510  (i.e., the electromagnets substantially covered by the base  1510  and not affected by changes induced by base edge transition over the electromagnet) may be employed for Z axis position determination while the leading and trailing electromagnets may be employed for X-Y position determination (see also  FIG.  26    where electromagnet M 2 C 1  is substantially completely covered by the base  1510  so as to have a known power factor, inductance, and/or phase lag with the base travelling at the predetermined height H of the drive plane  1598 , which known power factor, inductance, and/or phase lag is employed as a reference for Z height determination; however, in other aspects, any of the electromagnets may provide for a combined determination of X and/or Y positioning as well as Z positioning where the controller  199  is programmed to correlate the increase or decrease in the inductance, a phase lag/amplitude, and/or power factor that effects the Z position of the base  1510  with the increase or decrease in the inductance, phase lag/amplitude, and/or power factor with the X and/or Y position of the base  1510 . 
     As can be seen above, the aspects of the disclosed embodiment provide for self-deterministic base (reaction platen) absolute position feedback/determination of the base  1510  (and wafer handler  1500 ) in the X, Y, and/or Z directions by employing the electromagnets of the array of electromagnets  1700  for position determination. The aspects of the disclosed embodiment also provide for the yaw/angular position determination of the base  1510  (and wafer handler  1500 ) with the electromagnets of the array of electromagnets  1700 . Here, the position determination structure/features of the disclosed embodiment are in situ with (e.g., are one and the same with) the levitation and drive electromagnets so as to form a self-deterministic reaction platen (absolute) position feedback system that provides a more compact transport chamber  118  compared to substrate/wafer transport systems employing dedicated sensors for position determination of the wafer handler. 
     Referring to  FIG.  40   , a control system network  3999  that has a clustered architecture representative of the actuator control system network  1799  will be described. In the example illustrated in  FIG.  40   , there are three drive lines  177 ,  179 A,  179 B, each having respective array of electromagnets forming respective tracks  1550 A- 1550 F (though shown as linear, may be arcuate). For example, drive line  177  is formed by tracks  1550 A and  1550 B having electromagnets  177 ER 1 - 177 ERn and  177 EL 1 - 177 ELn. Drive line  179 A is formed by tracks  1550 C and  1550 D having electromagnets  179 AER 1 - 179 AERn and  179 AEL 1 - 179 AELn. Drive line  179 B is formed by tracks  1550 E and  1550 F having electromagnets  179 BER 1 - 179 BERn and  179 BEL 1 - 179 BELn. The configuration of the electrical machine illustrated in  FIG.  40    is exemplary and may have any other suitable configuration. 
     In  FIG.  40    the control system network includes the master controller  1760 , cluster controllers  3950 A- 3950 C and local controllers  1750 DL,  1750 DLA,  1750 DLB. Local controller  1750 DL corresponds to drive line  177 , local controller  1750 DLA corresponds to drive line  179 A, and local controller  1750 DLB corresponds to drive line  179 B. Each of the local controller(s)  1750 DL,  1750 DLA,  1750 DLB is substantially similar to distributed local drive controllers  1750 A- 1750   n  so that each drive line  177 ,  179 A,  179 B includes a distributed arrangement of local drive controllers  1750 A- 1750   n  as described above with respect to  FIG.  17    for controlling respective groups  1700 G 1 - 1700 Gn of electromagnets  1700 A- 1700   n.    
     In one aspect, as shown in  FIG.  40    each of the local controllers  1750 DL,  1750 DLA,  1750 DLB is connected (e.g., through a wireless and/or wired connection) to a respective cluster controller  3950 A- 3950 C. For example, each of the local controllers  1750 DL of drive line  177  are coupled to cluster controller  3950 B, each of the local controllers  1750 DLA of drive line  179 A are coupled to cluster controller  3950 A, and each of the local controllers  1750 DLB of drive line  179 B are coupled to cluster controller  3950 C. In other aspects, the local controllers may be connected (e.g., through a wireless or wired connection) directly to the master controller  1760  as shown in  FIG.  17   ). In still other aspects, the local controllers may be connected (e.g., through a wireless or wired connection) to both the master controller  1760  and the respective cluster controller  3950 A- 3950 C to provide redundant substantially failsafe control of the local controllers. 
     Each of the cluster controllers  3950 A- 3950 C are connected (e.g., through a wireless or wired connection) to the master controller  1760 . Each of the master controller  1760 , cluster controllers  3950 A- 3950 C, and local controllers  1750 DL,  1750 DLA,  1750 DLB includes any suitable processors and non-transitory computer program code to effect motion control and/or position determination of the substrate handlers  1500  as described herein. The master controller  1760  supervises the overall operation of the control system network  3999 , each of the cluster controllers  3950 A- 3950 C supervises the operations of the respective local controllers  1750 DL,  1750 DLA,  1750 DLB, and each local controller  1750 DL,  1750 DLA,  1750 DLB is utilized to drive the electromagnets and/or provide position feedback (of a substrate handler  1500 ) corresponding to the respective drive lines  177 ,  179 A,  179 B. 
     The clustered architecture provides the features of a centralized control network and the features of a distributed control network where required, within the network topology. The architecture as disclosed herein is advantageous because clusters may be distributed where required within the network, and each cluster controller  3950 A- 3950 C is capable of providing highly centralized control within the cluster it manages. Network traffic associated with highly centralized control is generally confined within each cluster and local controllers  1750 DL,  1750 DLA,  1750 DLB, where the cluster and local controllers  1750 DL,  1750 DLA,  1750 DLB may be located close to electromagnets to which they control, reducing problems associated with power and signal cabling. In addition, the clustered architecture allows for direct control of the local controllers  1750 DL,  1750 DLA,  1750 DLB by the master controller  1760  where required. Furthermore, because intense network traffic is generally confined within the clusters, and the clusters are capable of a high level of control, the architecture may accommodate a large number of clusters. Thus, the architecture provides a high level of scalability and allows for an efficient distribution of controllers. It is noted that while a clustered control architecture is described above, clustered architecture is merely an example of a suitable control architecture, although any suitable control architecture may be employed. 
     In another aspect of the disclosed embodiment, the local controllers  1750 DL,  1750 DLA,  1750 DLB shown in  FIG.  40    can be directly connected to the master controller  1760 . In this aspect, the master controller software is responsible for (e.g., the master controller is configured to control) several aspects of the real time control of the wafer handler&#39;s motion and the local controllers would be responsible (e.g., configured for) all low level feedback and actuation aspects of the control architecture. 
     Still referring to  FIG.  40    and also to  FIGS.  15 A- 16 C , in accordance with aspects of the disclosed embodiment, the processor  3901  of the master controller  1760  is programmed with a dynamic model  3910  of the base  1510  (e.g., the dynamic model is stored in any suitable memory  3902  accessible by the processor  3901 ) with a payload (e.g., substrate(s) S) thereon and without a payload. The processor  3901  is also programmed with a dynamic model  3911  of frictional forces p between the substrate S and the end effector  1520 . A form factor  3912  of the machine electronics (e.g., number of electromagnets, spacing between electromagnets, number of drive lines and their respective orientations, propulsion to lift relationship, etc.) relative to the base  1510  may also be stored in memory  3902  and accessible by the processor  3901 . 
     The master controller  1760  is programmed or otherwise configured to determine kinematic motion of the base  1510  from an initial substrate handler pose to a final substrate handler pose. The master controller  1760  is also programmed or otherwise configured to determine the kinematics of attitude/yaw control (in three degrees of freedom—pitch, roll, yaw) related to the determined kinematic motion. In one aspect, the kinematic motion and the kinematics of attitude/yaw are determined e.g., using one or more of dynamic model  3910 , dynamic model  3911  and form factor  3912  in combination with a predetermined substrate process recipe (e.g., where and when the substrate is to be transferred and what process is to be performed on the substrate). 
     One method for controlling a machine such as the electrical machines described herein is to calculate a trajectory for each of propulsion (along the X and/or Y axes), lift (along the Z axis), roll, pitch, yaw. Such trajectories can be conveniently defined by a series of position, velocity and time values grouped into frames, referred to as PVT frames. 
       FIG.  41 A  shows an exemplary PVT frame  4005 . The PVT frame  4005  includes position data  4010  (which may include start location (X,Y,Z), end location (X,Y,Z), and attitude (roll, pitch, yaw), velocity data  4015 , and time data  4020 . In one aspect the data is in binary format grouped together in one or more bytes. In another aspect each of the position data  4010 , velocity data  4015 , and time data  4020  occupies four bytes (while in other aspects the each of the position data  4010 , velocity data  4015 , and time data  4020  occupies more or less than four bytes). PVT frame  4005  may optionally include header information  4025  and trailing information  4030 , both of which may include identification, parity, error correction, or other types of data. PVT frame  4005  may include additional data of varying lengths or amounts between or among the header, position, velocity, time, and trailing data. It should be noted that the PVT frame  4005  is not limited to any particular length. In other aspects, the PVT frame is either reduced to a PT frame or a P frame only. The communication from the master controller  1760  to the cluster/local controllers  1750 DL,  1750 DLA,  1750 DLB,  1850 DL,  1850 DLA,  1850 DLB may include different sets of values, which are peripherally related to the desired motion, for example, these values could be frequencies, phase offsets, current values and/or voltage values of the electromagnets/coil under control. The master controller  1760  implements the desired algorithmic transformation, calculates and streams via the motion network such quantities (effectively to every coil through an hierarchical scheme of cluster and local controllers). 
     It is a feature of the aspects of the disclosed embodiment to use these series of values as inputs for the dynamic models  3910 ,  3911  of the controlled electrical machine to calculate theoretical lift forces and propulsion forces to be applied by predetermined electromagnets  1700 A- 1700   n  so that the base  1510  follows the desired trajectory. It is also a feature of the aspects of the disclosed embodiment to use elements of the dynamic models  3910 ,  3911  to scale feedback control signals used by the local controllers  1750 DL,  1750 DLA,  1750 DLB for each electromagnet under their control. 
     The lift forces, propulsion forces, and scaling terms may advantageously account for non linearities and dynamic cross coupling among individual drive lines  177 ,  179 A,  179 B. The lift forces, propulsion forces may be referred to herein as feedforward terms and the scaling term may be referred to as a gain term. 
     Using the electrical machine  1599  shown in  FIG.  40    (also referring to  FIGS.  15 A- 16 C ) as an example, the master controller  1760  may generate a trajectory for each drive line  177 ,  179 A,  179 B, along which a substrate handler  1500  is to travel, in terms of a commanded position, velocity and acceleration. Using an inverse kinematic model of one or more of the base  1510  and/or frictional forces μ, the master controller  1760  may utilize the trajectory information to generate corresponding feedforward, and gain terms. These terms may be grouped together with the trajectory information in frames specific to each drive line  177 ,  179 A,  179 B, referred to as PVT-FG frames.  FIG.  41 B  illustrates an exemplary PVT-FG frame  4095 . PVT-FG frame  4095  includes optional header  4025 , position data  4010 , velocity data  4015 , time data  4020 , and optional trailing information  4030 , similar to PVT frame  4005 . In addition, PVT-FG frame  4095  includes at least one feedforward term  4050  and at least one gain term  4060 . The data may be in binary format grouped together in one or more bytes. In one aspect of the PVT-FG frame  4095  the position data  4010 , velocity data  4015 , time data  4020 , feedforward term  4050 , and gain term  460  each occupy four bytes (while in other aspects they may each occupy more or less than four bytes). Similar to PVT frame  4005 , PVT-FG frame  4095  may include other data of varying lengths or amounts, distributed among or between the various terms. 
     The PVT-FG frames may (or in other aspects the PVT frames) then be distributed over the control system network  3999 . The cluster controllers  3950 A- 3950 C, receive the data, and may interpolate between two consecutive frames to obtain an instantaneous position, velocity, feedforward term and gain value, and utilize this information to effect control of the substrate handler  1500 . For example, each cluster controller  3950 A- 3950 C employs the PVT-FG frames (or in some aspects the PVT frames), or other suitable information/commands, from the master controller  1760  to generate the propulsion forces Fx (propulsion force along the X axis), Fy (propulsion force along the Y axis), and lift force Fz (along the Z axis) to effect one or more of levelling, propulsion, and three degree of freedom attitude control (e.g., roll, pitch, yaw) of the substrate handler  1500  and base  1510  thereof. In some aspects, the form factor  3912  of the machine electronics may be programmed at the cluster controller  3950 A- 3950 C level, rather than or in addition to being programmed in the master controller  1760 , where the form factor is used to establish the lift to propulsion relationship(s), and with the data provided by the master controller  1760  to generate the lift and propulsion forces noted above. In other aspects, the cluster controllers  3950 A- 3950 C and local controllers  1750 DL,  1750 DLA,  1750 DLB may receive corresponding data from the master controller  1760 , and utilize the data to control the electromagnets  1700 A- 1700   n  and movement of the substrate handler  1500  along one of more of the drive lines  177 ,  179 A,  179 B. 
     The cluster controllers  3950 A- 3950 C (or alternatively the local controllers  1750 DL,  1750 DLA,  1750 DLB) command electromagnet  1700 A- 1700   n  modulation, which commands are sent to and received by the respective local controllers  1750 DL,  1750 DLA,  1750 DLB, to effect one or more of dynamic phase allocation and the creation of virtual multiphase motor actuator/position units as described in greater detail herein. 
       FIG.  29 A  illustrates an exemplary controlled motion(s) of the substrate handler  1500  in accordance with aspects of the disclosed embodiment with respect to increased substrate handler throughput while carrying a substrate S. Here, the controller  199  controls the levitation forces (e.g., FZ T , FZ L ), generated by the array of electromagnets  1700 , so as to impart differential levitation forces (illustrated in  FIG.  21   ) across the base  1510  that effect a controlled inclination (e.g., e+ or e−) of the base  1510 , relative to the drive plane  1598 , that controls a predetermined reaction platen attitude in at least one of pitch (shown in  FIGS.  15 B,  29 A and  35   ) and roll (shown in  FIGS.  15 A and  37   ). In one aspect, the controller  199  controls the levitation forces (e.g., FZ T , FZ L ), generated by the array of electromagnets  1700  of the motor actuator units (that are virtually moving), so as to effect a predetermined bias attitude BA+ or BA− of the base  1510 , relative to the drive plane  1598 , that imparts a bias reaction force F 2  ( FIG.  31   ), from a base payload seating surface (e.g., such as a substrate seating surface  1520 SS ( FIGS.  31 ,  33 A,  33 B ) of the end effector  1520  or a seating surface defined by substrate supports of cart  1431 - 1433  of cart  1500 C) on a substrate S supported by the base seating surface, in a direction countering payload inertial force arising from acceleration of the reaction platen along the drive plane  1598 . The controller  199  is configured to determine acceleration of the base  1510  (and the substrate handler thereof) along the drive plane  1598  at least from changes in the position of the base  1510  as determined based on changes in predetermined excitation characteristic (such as, e.g., inductance, phase lag/amplitude, and/or power factor—as described herein), and in response to the acceleration determine, control the bias attitude of the base  1510  to provide the predetermined bias attitude countering the payload inertial force arising from the acceleration of the base  1510 . In other aspects the controller  199  may apply a predefined acceleration from commanded trajectory for bias attitude control. Here, the controller  199  controls excitation of the electromagnets  1700 A- 1700   n  of the virtually moving motor actuator units of the array of electromagnets  1700  so as to set the bias attitude BA+ or BA- to bias the base  1510  against inertial forces tending to displace a substrate S, seated against the base  1510  (e.g., on an end effector  1520  thereof or substrate supports  1431 - 1433  thereof), relative to the base  1510  along a seat between the substrate S and the base  1510  (see, e.g.,  FIGS.  23 ,  25 A,  25 B ). 
     As an example of countering payload inertial forces, starting at the left-hand side of  FIG.  29 A , a substrate handler  1500  (which may be any of the substrate handlers described herein) is depicted at a starting point of a motion in direction  2122  in  FIG.  29 A . As the substrate handler begins to move, a set of propulsion force vectors FP and lift force vectors FZ are generated by the Control System (e.g., the actuator control system network  1799  which may be part of controller  199 ) so as to cause the substrate handler  1500  to accelerate in the motion direction with an increased Pitch angle e+(e.g., the end effector  1520  is tilted in, e.g., a clockwise direction). To effect the increased pitch angle e+ the lift force vectors FZ are generated so that a magnitude of a trailing lift force vector FZ T  is larger than a magnitude of a leading lift force vector FZ L  (where leading and trailing are in reference to the motion direction). As the substrate handler reaches approximately its halfway point towards the end of the motion (e.g., such as where there is substantially zero acceleration of the substrate handler  1500 ), the pitch angle e+ is reduced in magnitude so that the tilted orientation of the end effector  1520  is reversed from the clockwise orientation to zero (e.g., substantially parallel with the level reference plane  1299 —the trailing lift force vector FZr and the leading lift force vector FZ L  are substantially equal). At this point in the trajectory, the substrate handler  1500  motion begins a deceleration stage where the pitch angle e− is decreased so that the end effector  1520  pitches to a counter clockwise orientation. To effect the decreased pitch angle e− the lift force vectors FZ are generated so that the magnitude of the trailing lift force vector FZ T  is less than a magnitude of the leading lift force vector FZ L ). As the substrate handler  1500  reaches its final destination, the pitch angle e− is increased to zero so that the tilted orientation of the end effector  1520  is substantially parallel with the level reference plane  1299 , as in the start of the motion. 
     As may be realized, while the pitch of the end effector is increased or decreased to account for acceleration and deceleration of the substrate handler  1500  substantially without slippage of the substrate S relative to the end effector while travelling along a substantially straight/linear path (such as along drive lines  177 - 180 ), in other aspects, the roll r and/or pitch e of the substrate handler  1500  may be increased or decreased to provide for higher rotational accelerations of the substrate handler  1500  (such as about one or more of axes  777 ,  1277 ,  1377  in a manner substantially similar to that described above with respect to the linear motion (see  FIG.  29 B  which illustrates rolling of the end effector in rotation direction with roll control as shown in  FIG.  15 A  where lift force vector FZ left  is greater than lift force vector FZ right ). 
     The motion control illustrated in  FIG.  29 A  effects a substantially faster substrate motion transport (e.g., provides for higher accelerations substantially without substrate slippage relative to the end effector) when compared to conventional substrate transport where the end effector is parallel with the wafer transfer plane throughout end effector motion. As an example, if the pitch angle e of  FIG.  29 A  is set to be zero (as with conventional substrate transports) during the entire motion then the maximum allowable propulsion acceleration is limited to the static coefficient of friction (p) between the substrate S and a contact surface of the end effector  1520 . This is illustrated in  FIG.  30   , which constitutes the typical use case in a conventional substrate transport where the substrate S is held by its back side in contact with the end-effector. As it can be seen in  FIG.  30   , the maximum acceleration imposed to the substrate S is μg before wafer slippage takes place. Where “g” is the acceleration of gravity (about 9.8 m/S 2 ), μ is the coefficient of friction, M is the mass of the substrate, W is the weight of the substrate, and N is the normal force. 
       FIG.  31    illustrates the case where the substrate S (having a mass m) is carried by substrate handler  1500  (having a mass M) with a pitch angle e while the substrate handler  1500  is accelerated in the X direction. The force diagrams in  FIG.  31    illustrate the dynamics of the motion of the substrate S and substrate handler  1500 . In  FIG.  31   , the substrate hander  1500  is accelerated along the propulsion direction X with acceleration a. As a result, the force at the substrate handler is represented by the variable F 1 . The acceleration a along the X direction, impacts the reaction (normal) force N on the substrate S in a way that once added to the weight of the substrate W yields a resultant wafer force F 2 . It is possible to relate the angle e and the acceleration a in such a way that the substrate S substantially does not slip relative to the end effector  1520  of the substrate handler  1500 . To substantially prevent wafer slippage, two situations can be considered for the sake of clarity. First, it is assumed that there is no friction between the substrate and the end effector  1520 .  FIG.  32 A  illustrates a free body diagram of the substrate S on the end effector  1520  in the absence of friction μ. As can be seen in  FIG.  32 A , despite the absence of friction μ, an acceleration a can be determined in terms of the pitch angle e such that the substrate mass m is traveling along the X direction. This relation is expressed by equation 16 below: 
         a=g  tan  e   [eq. 16]
 
     where g is the acceleration of gravity (9.8 m/s 2 ).  FIG.  32 B  illustrates wafer slippage regions in terms of the pitch angle e. It is noted that the substrate S will slip relative to the end effector  1520  without friction μ if the pitch angle e is substantially zero. The curve illustrated in  FIG.  32 B  represents the desired pitch angle “e” to keep the substrate S moving at an acceleration “a” along the X direction without slippage. Alternatively, the same curve of  FIG.  32 B  can be interpreted as the demanded acceleration “a” of the substrate handler  1500  to prevent the substrate S from slipping while moving along the X direction with the pitch angle “e”. Deviation from the curve illustrated in  FIG.  32 B  will cause the substrate S to slide either “downhill” or “uphill” (where the terms downhill and uphill are used for convenience relative to the pitch) relative to the end effector  1520  depending on the acceleration value. 
       FIGS.  33 A and  33 B  show the effect of a non-zero static friction coefficient μ on the relation between acceleration a and pitch angle e. For example,  FIG.  33 A  illustrates a minimum propulsion acceleration before slippage of the substrate S relative to the end effector  1520  takes place. In this case, the friction force direction points “uphill” to substantially prevent the wafer mass m from sliding “downhill” (again relative to the direction of pitch). Here, the “slowest” expected acceleration to prevent wafer slippage is calculated as: 
         a   min =[−μ+tan  e ]/[1+μ tan  e ]  [eq. 17]
 
       FIG.  33 B , illustrates the case for the maximum (e.g., fastest) expected propulsion acceleration a before slippage of the substrate S relative to the end effector  1520 . In this case, the friction force direction points “downhill” to substantially prevent the wafer mass m from sliding “uphill” (again relative to the direction of pitch). Here, the “fastest” expected acceleration a is calculated as: 
         a   max =[μ+tan  e ]/[1−μ tan  e ]  [eq. 18]
 
     Consequently, in the presence of a non-zero static friction coefficient μ the propulsion acceleration a should stay within the limits below in order to prevent substrate S slippage, for a given pitch angle: 
         a   min   &lt;a&lt;a   max   [eq. 19]
 
       FIG.  34    provides an example of the dependency between acceleration a and pitch angle e for a static coefficient of μ that is about 0.1, which is a typical value for substrate handlers used in high temperature applications. The curve of  FIG.  32 B  is repeated in  FIG.  34    under the case of μ equal to about 0. The region between the top and bottom curves (μ equal to about 0.1) represents a non-slippage region (e.g., a region of acceleration for a given pitch angle where the substrate slippage relative to the end effector substantially does not occur). The areas outside this region may have wafer slippage either in the upwards of downwards direction relative to the substrate handler inclination (i.e., pitch angle e). In the example of  FIG.  34   , the maximum acceleration with a substantially zero pitch angle is about 0.1 g which is the fastest acceleration that conventional substrate handlers can provide for typical high temperature applications. If the pitch angle e is set to about 16 degrees of inclination, the substrate can be transported at accelerations as high as 0.4 g using the same end effector material (as in conventional substrate handlers) which constitutes a substantial throughput improvement compared to the conventional substrate handlers. The pitch angle e can be set according to a predetermined acceleration in order to maximize throughput such as depicted in  FIG.  29 A . 
       FIG.  35    illustrates active control of the substrate handler  1500  orientation in roll, pitch, and yaw with respect to leveling of the substrate handler  1500  relative to a substrate station, such as process module  120 . Mechanical deflection imposes challenges on entering and exiting process module openings  2780  which are becoming increasingly smaller in height H 3  due to the need of optimizing process module  120  process times. Conventional substrate transports generally suffer from the inherent potential of mechanical deflection due to the presence of articulated links with bearings that add weight and decrease stiffness, noting that compensating for the end-effector orientation as the wafer goes through the process module opening  2780  may not be practical. In these cases, it is becoming increasingly difficult to be able to comply with more restrictive mechanical deflection constraints. The aspects of the disclosed embodiment provide a solution to mechanical deflection that dynamically compensates for any mechanical deflection by controlling the substrate handler orientation in space, relative to the level reference plane (e.g., by adjusting the roll, pitch and yaw angles as described herein) such that a substrate passes through the process module opening  2780  substantially without contact between the substrate S and the opening  2780  and substantially without contact between the end effector  1520  and the opening  2780 . 
       FIGS.  15 A- 16 C  illustrate the controlled adjustment, by the local drive controller(s)  1750 A- 1750   n  (and based on the position determination of the wafer handler  1500  as described herein), of the roll and yaw angles of the substrate handler  1500  in addition to the pitch angle. Referring also to  FIG.  35   , the controlled adjustment of each of the roll, yaw, and pitch angles (e.g., by differentially varying at least the lift force vectors acting on the base  1510  as described herein) effects leveling a position of the substrate handler  1500  at any suitable substrate holding station such as a process module  120  so that a plane  2770  of the substrate S (and end effector  1520  on which the substrate S is supported) is substantially the same as a plane  2771  defined by the substrate holding station  120  substrate support surface  2760 . In some aspects, the roll, yaw, and pitch angles are adjusted independent of each other. The controlled adjustment of the substrate handler  1500  orientation angles (e.g., roll, pitch, and yaw) also provides for compensation of mechanical deflection of the end effector  1520  due to, for example, the substrate loading as well as the weight of the substrate handler  1500  structure. 
     Referring to  FIGS.  8 - 11  and  36  and  37   , as described above, in some aspects multiple drive lines  177 ,  178  are provided so as to extend longitudinally along a length of the transport chamber  118  to provide passage of one substrate handler  1500  by another substrate handler along the longitudinal direction of the transport chamber  118 .  FIG.  36    illustrates passage of two substrate handlers  1500 A,  1500 B past one another with substrate handler  1500 A traveling along an inbound track  1550 A and with substrate handler  1500 B travelling along an outbound track  1550 B. Here each of the substrate handlers  1500 A,  1500 B have roll, pith, and yaw angles so that the plane  2770  of the end effector  1520  (and substrate s held thereon) is substantially parallel (i.e., level) with the level reference plane  1299 . Here, with the end effectors  1520  level, the transport chamber  118  has a lateral width W 1 . However, in accordance with aspects of the disclosed embodiment, the width of the transport chamber  118  may be minimized or otherwise reduced from lateral width W 1  to lateral width W 2  by adjusting one or more of the roll, the pitch, and the yaw of the substrate handlers  1500 A,  1500 B as they pass one another along the length of the transport chamber  118 . For example, as illustrated in  FIG.  37    the roll angle of each substrate handler  1500 A,  1500 B may be adjusted to a predetermined angle β relative to the level reference plane  1299  to avoid contact between the substrate handlers  1500 A,  1500 B as they move past one another during a period of time that both substrate handlers  1500 A,  1500 B would otherwise occupy the same space. The predetermined roll angle β may depend on end effector configuration (e.g., so that the substrate S does not slip relative to the end effector). As may be realized it advantageous to have control of the roll, pitch, and/or yaw angles of each substrate handler  1500  in order to reduce a footprint of the transport chamber  118  that houses the wafer handling automation, where the reduced footprint at least increases tool density on the fabrication facility floor and decreases pump down times of the transport chamber which may result in increased throughput. 
     Referring now to  FIGS.  17  and  38   , an exemplary control of the array of electromagnets  1700  will be described where dynamic phase allocation is employed. As described herein, the controller  199  (which in one aspect is a clustered or master controller as described herein—see  FIG.  40   ) is operably coupled to the array of electromagnets  1700  and the alternating current power source  1585  (the power source may be any suitable type and can be direct current in which case the controller driving circuit will modulate that to desired frequency/phase for as many alternating current power phases as desired) and configured so as to sequentially excite the electromagnets  1700 A- 1700   n  with multiphase alternating current so that the base  1510  of a substrate handler  1500  is levitated and propelled with at least one of attitude control and yaw control with a common set of the electromagnets  1700 A- 1700   n  (such as those electromagnets of a respective drive line  177 - 180 ). As noted above, the controller  199  is configured to sequentially excite the electromagnets  1700 A- 1700   n  cooperating in multi-phase alternating current excitation that form motor actuator units  1701  corresponding to the position of the base  1510  as determined based on the changes in the excitation characteristic (e.g., inductance, a phase lag/amplitude, and/or power factor) as described herein. The number n (an integer in the example of three or more, though in other aspects may be two or more) of electromagnets  1700 A- 1700   n  of each motor actuator unit  1701  as well as the location (static) of the respective n electromagnets  1700 A- 1700   n  of each motor actuator unit  1701  are dynamically selectable by the controller  199  in effecting lift and propulsion of the base (secondary)  1510  at any given time throughout operation of the motor actuator. Each of the electromagnets  1700 A- 1700   n  generates, from excitation with common multiphase alternating current having a single common frequency per phase, both the separately controllable levitation and the propulsion forces against the base  1510  so as to control the base  1510  with up to six independent degrees of freedom including at least one of attitude and yaw at least with the base  1510  levitated. The common single frequency per phase of each phase (here respective phases A, B, C) may be selectably variable from different desired excitation frequencies so that levitation and propulsion forces generated by the motor actuation unit  1701  enable substantially independent control of the base  1510  in each of the up to six independent degrees of freedom. In one aspect, the controller  199  controls the roll, pitch, and yaw angles generated by the array of electromagnets  1700 A- 1700   n  arranged in the respective motor actuator units  1701 , including at least the attitude with the base  1510  levitated and propelled so as to move relative to the array of electromagnets  1700  along the at least one drive line  177 - 180  from a first predetermined position P 1  (see  FIG.  1 B ) with respect to the frame of the chamber  118  to a second different predetermined position P 2  (see  FIG.  1 B ) with respect to the frame of the chamber  118 . In one aspect, the controller  199  controls the roll, pitch, and yaw angles generated by the array of electromagnets  1700 , including at least the base  1510  attitude and the base  1510  yaw with the base  1510  levitated and stationary relative to the array of electromagnets  1700  in a predetermined position (such as position P 2  in  FIG.  1 B ) along the at least one drive line  177 - 180  with respect to the frame of the chamber  118 . 
       FIGS.  39 A and  39 B  illustrate an example where each electromagnet (or coil unit)  1700 A- 1700   n  is grouped so as to define a motor actuator unit  1701  having a dynamically selected number of electromagnets, for example three electromagnets (n=3) and three corresponding phases (m=3) with an electrical angle between the phases of  1200  (see also  FIG.  17   ) is also dynamically associated with the three different phases A, B, C so that association of each phase A, B, C with the corresponding static electromagnet  1700 A- 1700   n  comports with the dynamic state of the motor actuation unit  1701 . Accordingly, with the electromagnets of the motor actuator unit  1701  propelling the base  1510  (and sensing the position of the base  1510 ) (e.g., along direction  3100 ) each phase A, B, C respectively changes or moves from one static electromagnet to another (i.e., rolling the designation or allocation of the respective phases to consecutive electromagnets  1700 A- 1700   n  so as to generate a virtual (motion) multi-phase actuator/position sensing unit  3000 ,  3000   t P 1 ,  3000   t P 2  of each of the linear electrical machine  1599  and the electrical machine  1599 R proceeding in the direction of motion  3100  commensurate with motion of the base  1510  generated by the excitation of the electromagnets  1700 A- 1700   n  corresponding to the virtual motion multi-phase actuation unit  3000 ,  3000   t P 1 ,  3000   t P 2 . This dynamic relationship or association producing the virtual motion multi-phase actuator unit  3000 ,  3000   t P 1 ,  3000   t P 2  between coil units and phase will be referred to here for convenience as “dynamic phase allocation” wherein the virtual motion of the representative virtual motion multi-phase actuator unit  3000 ,  3000   t P 1 ,  3000   t P 2  effecting propulsion of the base  1510  is illustrated schematically in  FIG.  38    (see also  FIG.  17   ). Here the virtual motion multi-phase actuator/position sensing unit (or “MAU” in  FIG.  17   )  3000  has dynamically selected three electromagnets and associated phases A, B, C, shown in an initial (representative) position P=0 at time t=t 0 . The respective excitation of the virtual motion multi-phase actuator unit  3000  electromagnets generate propulsion forces that move the platen/base  1510  between t 1  and t 2  (see also  FIGS.  39 A and  39 B ). Here, as shown, at P=0 and t=t 0 , electromagnets  1700 A- 1700 C are grouped to form virtual motion multi-phase actuator unit  3000 , and are respectively associated with phases A, B, C. Coincident with generation of propulsion forces Fx, respective excitation of virtual motion multi-phase actuator unit  3000  electromagnets  1700 A- 1700 C generate separately controllable lift forces Fy with a controlled variable height relative to the platen/base  1510 , that simultaneously lifts and effect tilt adjustment of the platen/base  1510  simultaneously with propulsion (see  FIGS.  39 A and  39 B ). As may be realized, under effect of the lift Fy and propulsion Fx forces imparted by the respective electromagnets  1700 A- 1700 C of the virtual motion multi-phase actuator unit  3000  at time t=t 0  and position P=0 the platen/base  1510  moves (relative to the transfer chamber and hence the static electromagnets  1700 A- 1700 C) with a predetermined lift and tilt. To maintain steady state tilt of the platen/base  1510  during motion away from the group of electromagnets  1700 A- 1700 C (defining virtual motion multi-phase actuator unit  3000  at P=0 and T=TO) the controller  199  and circuitry  3050 , of the respective electromagnets of the electromagnet array  1700 A- 1700   n , are configured to dynamically “move” (or “change”) the allocation of the respective phases A, B, C (from the initial virtual motion multi-phase actuator unit  3000  at P=0 and t=t 0 ) commensurate with the travel of the platen/base  1510  at time t=t 1  and position P=1 to corresponding electromagnets  1700 B- 1700 D that now define virtual motion multi-phase actuator unit  3000   t P 1  disposed at position P=1 at time t=t 1 , and subsequently allocation of the respective phases A, B, C (from the virtual motion multi-phase actuator unit  3000   t P 1  at P=1 and t=t 1 ) commensurate with the travel of the platen/base  1510  at time t=t 2  and position P=2 to corresponding electromagnets  1700 C- 1700 E that now define virtual motion multi-phase actuator unit  3000   t P 2  disposed at position P=2 at time t=t 2 , and so on. Dynamic phase allocation is repeated throughout platen/base  1510  motion so that the phase distribution with respect to the platen, and excitation by respective phases (here A, B, C) of the platen/base  1510  remain substantially steady state throughout motion of the platen/base  1510 . 
     The virtual multi-phase actuator/position sensing unit  3000 ,  3000   t P 1 ,  3000   t P 2  may comprise a series of electromagnets  1700 A- 1700   n  of the array of electromagnets  1700  coupled to at least the multiphase alternating current power source  1585  that define at least one drive line  177 - 180  within the drive plane  1598 , where electromagnets  1700 A- 1700   n  in the series of electromagnets  1700 A- 1700   n  are dynamically grouped into at least one multiphase actuator unit DLIM 1 , DLIM 2 , DLIM 3 , and each of the at least one multiphase actuator unit DLIM 1 , DLIM 2 , DLIM 3  being coupled to at least the multiphase alternating current power source  1585 . In this case, on initiating propulsion (effecting motion of the base/secondary) by excitation of corresponding electromagnet groups of the motor actuation unit at an initial position (P=0, t=0) the definition of phases A, B, C and the associated “motors” (e.g., DLIM 1 , DLIM 2 , DLIM 3 ) are changing in space and time (Pi, ti), as described above, in order to maintain substantially steady state force vectors FZ 1 , FZ 2 , FX 1 , FX 2  imparted on the base  1510  throughout the range of motion, that provide a desired substantially steady state or constant tilt orientation of the substrate handler  1500  throughout the range of motion. As noted herein, an exemplary actuator control system network  1799  configured to effect dynamic phase allocation is described with respect to  FIG.  17   . As can be seen in  FIGS.  39 A and  39 B , the dynamic phase allocation is controlled by the controller  199  so that the respective electromagnets  1700 A- 1700   n  grouped into corresponding motor actuation units (such as described herein) energized by the multiphase alternating current A, B, C present, with respect to the base  1510  (represented by the front portion  3110  and rear portion  3111 ), a substantially steady state multiphase distribution across respective electromagnets  1700 A- 1700   n  of the virtually moving at least one multiphase actuator unit DLIM 1 , DLIM 2 , DLIM 3 . It is noted that the phase currents A, B, C are illustrated within respective electromagnets  1700 A- 1700   n  and the phase current distribution across the at least one multiphase actuator unit DLIM 1 , DLIM 2 , DLIM 3  remains constant or steady state with respect to the base  1510  (e.g., as an example of steady state note phase current A remains at the trailing end of the rear portion  3111 , phase current C remains at the leading end of the rear portion  3111 , and phase current B remains in the center of the rear portion  3111  throughout movement of the base  1510  and the at least one (virtually moving) multiphase actuator unit DLIM 1 , DLIM 2 , DLIM 3  in the direction  3100 ). 
     In greater detail of dynamic phase allocation,  FIG.  38    depicts at time t 1  electromagnets  1700 A,  1700 B,  1700 C which are respectively defined as phases A, B, C ( FIGS.  38  and  39 A ) which generate a spatial force vector(s) that provides separately controllable lift and propulsion forces of a predetermined wafer handler  1500  (i.e., a wafer handler identified by its unique signature as determined by the predetermined excitation characteristic (such as, e.g., a phase lag) of the electromagnets and selected for movement by the controller  199 ). As the substrate handler  1500  moves in space (e.g., along the drive line associated with the array of electromagnets  1700 ), at time t 2  electromagnets  1700 B,  1700 C,  1700 D respectively become phases A, B, C ( FIGS.  38  and  39 B ). As the substrate handler  1500  continues to travel along the drive line (which in this example is in direction  3100  as shown in  FIGS.  39 A,  39 B, and  39 C ), at time t 3  phases A, B, C are associated with electromagnets  1700 C,  1700 D,  1700 E, respectively. This dynamic phase allocation effects continuous spatial and time control of the force vectors that maintain propulsion, lift, and orientation of the predetermined substrate handler  1500 . In one aspect, the alternating current power source  1585  is coupled to each of the electromagnets  1700 A- 1700   n  of the array of electromagnets  1700  through any suitable signal conditioning circuitry  3050  which may include current amplification power supply units  3011  or any other suitable signal processing. The phase A, B, C currents are transmitted to each of the local drive controllers  1750 A- 1750   n  which, under control of or in response to instruction from, master controller  1760  provide a specified one of the phase A, B, C currents to the respective electromagnets in the manner noted above to effect dynamic phase allocation. 
     As described herein, the base  1510  ( FIG.  16 B ) of a substrate handler cooperates with the electromagnets  1700 A- 1700   n  of the at least one multiphase actuator unit ( FIG.  39 A ) DLIM, DLIM 2 , DLIM 3  so that excitation of the electromagnets  1700 A- 1700   n  with alternating current generates levitation and propulsion forces against the base  1510  that controllably levitate and propel the base  1510  along the at least one drive line  177 - 180 , in a controlled attitude relative to the drive plane  1598 . The controller  199  (which in some aspects includes at least the master controller  1760  and any controller subordinate to the master controller such as the local drive controllers  1750 A- 1750   n ; however in other aspects the controller may have any suitable configuration), is operable coupled to the alternating current power source  1585  and the array of electromagnets  1700 . The alternating current power source  1585  may include any suitable associated circuitry  3050  through which the alternating current power source  1585  is connected to the array of electromagnets  1700 . The alternating current power source  1585  is controlled by the local drive controllers or any other suitable controller such as the master controller  1760 . Typical control parameters for the alternating current power source comprise of signal amplitude, signal frequency, and phase shift relative to a reference coil unit. Other types of control parameters may be defined. As used herein the “phase” A, B, C as illustrated in  FIG.  38    is similar to a particular coil in a multi-phase electrical motor; however, the each of the phase definitions (such as A, B, C in  FIG.  38   ) is not physically tied to any particular coil. 
     As described before, and now referring to  FIG.  39 C  in one aspect, controlling propulsion and levitation simultaneously and separately (so that propulsion forces and lift forces are separately controllable in full, so that control of each may be deemed independent of one another though both forces are effected by excitation with common multiphase alternating current having a single common frequency per phase, the common frequency per phase is selectably variable from different desired frequencies) may be effected by a variant of the dynamic phase allocation described herein, where one or more dynamic linear motor (DLIM) may include a selectable n number of phases associated with electromagnets defining the virtual motion multi-phase actuator unit, where n can be an integer larger than three. The number n of electromagnets defining the virtual motion multi-phase actuator unit may be dynamically selected, for example, for effecting different moves of the platen/base  1510  depending on kinematic characteristics of the desired move. Here the excitation frequency commonly applied per phase of the virtual motion multi-phase actuator unit is selected by the controller  199  so as to generate desired kinematic performance and control of the platen/base  1510 . Here, the phase control algorithm maintains the same electrical phase angle difference between the phases (e.g., electromagnets of the motor), as shown in  FIG.  39 C . The electrical phase difference is calculated relative to a reference phase or relative to each phase. The electrical phase angle difference p between phases may have a range so as to produce positive and negative values of propulsion forces while maintaining levitation. Depending on the value of the electrical phase angle difference (p the number of electromagnets within a respective dynamic linear motor varies. Here, the boundary between DLIM 1  (illustrated for exemplary purposes with  6  electromagnets) and DLIM 2  as shown in  FIG.  32 C  is dynamic. In another aspect of the dynamic linear motor electromagnet/phase allocation, not all electromagnets of a dynamic linear motor need to be energized at the same time. Referring to DLIM  1 , only m (in this example m=4) electromagnets out of all n (in this example n=6) electromagnets of dynamic linear motor DLIM 1  (where m is the number of electromagnets covered by the base (or secondary)) are energized to effect lift and propulsion of the base  1510 , while the other electromagnets of the n electromagnets of the dynamic linear motor DLIM 1  can be turned off. 
     Referring to  FIGS.  1 A- 28  and  42    an exemplary method for a linear electrical machine (such as those described herein) will be described. In accordance with the method, the linear electrical machine  1599  is provided with a frame  118 M ( FIG.  42   , Block  4200 ) having a level reference plane  1299 . A drive plane  1598 , with an array of electromagnets  1700  connected to the frame  118 M, is formed ( FIG.  42   , Block  4210 ) at a predetermined height H relative to the level reference plane  1299 . The array of electromagnets  1700  is arranged so that a series of electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the array of electromagnets  1700  define at least one drive line (e.g., such as one or more of drive lines  177 - 180 ) within the drive plane  1598 , and each of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  being coupled to an alternating current power source  1585  energizing each electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 . At least one reaction platen  1510  (also referred to as a base) of paramagnetic, diamagnetic, or non-magnetic conductive material is provided ( FIG.  42   , Block  4220 ) and is disposed to cooperate with the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the array of electromagnets  1700 . The electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are excited ( FIG.  42   , Block  4230 ) with alternating current to generate levitation and propulsion forces against the reaction platen  1510  that controllably levitate and propel the reaction platen  1510  along the at least one drive line  177 - 180 , in a controlled attitude relative to the drive plane  1598  where the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are sequentially excited, with a controller (such as one or more of controllers  199 ,  1750 ,  1750 A- 1750   n  or other controller as described herein) operably coupled to the array of electromagnets  1700  and the alternating current power source, with multiphase alternating current with a predetermined excitation characteristic (e.g., inductance, phase lag/amplitude, and/or power factor as described herein) so that each reaction platen  1510  is levitated and propelled with up to six degrees of freedom. As described herein, vibration of the at least one reaction platen  1510  is compensated for with the passive vibration compensator or absorber  4700 A,  4700 B. The reaction platen position feedback is determined with the controller (such as with one or more of those controllers described herein) ( FIG.  42   , Block  4240 ), in at least one degree of freedom from the up to six degrees of freedom, from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  effecting levitation or propulsion of the reaction platen  1510 . The variance in the predetermined characteristic defines self-deterministic reaction platen position feedback of each of the at least one electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5 , of the array of electromagnets  1700 , effecting levitation or propulsion of the reaction platen  1510 . As described herein, vibration of the base  1510  is compensated for ( FIG.  42   , Block  4260 ) so that the end effector (and any wafers thereon) are substantially free of vibrations induced by the excitation of the electromagnets and levitation of the base  1510 . Temperature control of the reaction platen  1510  may also be effected ( FIG.  42   , Block  4250 ) where the at least one reaction platen  1510  is seated on the floor  118 L of the transport chamber  118  and/or the at least one reaction platen  1510  is replaced with another reaction platen  1510 ALT via the service lock SL. 
     Referring to  FIGS.  1 A- 28  and  43    an exemplary method for a linear electrical machine (such as those described herein) will be described. In accordance with the method, the electromagnetic conveyor substrate transport apparatus  1599  is provided with a chamber  118  ( FIG.  43   , Block  4300 ) configured to hold a sealed atmosphere therein. The chamber  118  has a level reference plane  1299  and at least one substrate pass through opening  1180  for transferring a substrate in and out of the chamber  118  through the opening  1180 . A drive plane  1598  is formed ( FIG.  43   , Block  4310 ) with an array of electromagnets  1700  connected to the chamber  118  at a predetermined height H relative to the level reference plane  1299 . The array of electromagnets  1700  is arranged so that a series of electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the array of electromagnets  1700  define at least one drive line (e.g., such as one or more of drive lines  177 - 180 ) within the drive plane  1598 . The electromagnets in the series of electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are grouped into at least one multiphase actuator unit, and each of the at least one multiphase actuator unit being coupled to a multiphase alternating current power source  1585 . At least one reaction platen of paramagnetic, diamagnetic, or non-magnetic conductive material is provided ( FIG.  43   , Block  4320 ) and is disposed to cooperate with the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the at least one multiphase actuator unit. The electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are excited ( FIG.  43   , Block  4330 ) with alternating current to generate levitation and propulsion forces against the reaction platen  1510  that controllably levitate and propel the reaction platen  1510  along the at least one drive line  177 - 180 , in a controlled attitude relative to the drive plane  1598 . The electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are sequentially excited, with a controller (such as those controller described herein) operably coupled to the array of electromagnets  1700  and alternating current power source  1585 , with multiphase alternating current with a predetermined excitation characteristic so that the at least one reaction platen  1510  is levitated and propelled. As described herein, vibration of the at least one reaction platen  1510  is compensated for with the passive vibration compensator or absorber  4700 A,  4700 B. Reaction platen position feedback is determined with the controller (such as those controllers described herein) ( FIG.  43   , Block  4340 ) from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen  1510 . The variance in the predetermined characteristic defines self-deterministic reaction platen position feedback of each of the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen  1510 . As described herein, vibration of the base  1510  is compensated for ( FIG.  43   , Block  4360 ) so that the end effector (and any wafers thereon) are substantially free of vibrations induced by the excitation of the electromagnets and levitation of the base  1510 . Temperature control of the reaction platen  1510  may also be effected ( FIG.  43   , Block  4350 ) where the at least one reaction platen  1510  is seated on the floor  118 L of the transport chamber  118  and/or the at least one reaction platen  1510  is replaced with another reaction platen  1510 ALT via the service lock SL. 
     Referring now to  FIG.  51   , and exemplary substrate S transfer operation will be described. It is noted that the substrate transfer operation described herein is applicable to the above-described each of the above described aspects of the disclosed embodiments. In the substrate transfer operation the electromagnets  1700 A- 1700   n ,  1700 A 1 - 1700   n   1 ,  1700 A 2 - 1700 N 2 ,  1700 A 3 - 1700   n   3 ,  1700 A 4 - 1700   n   4 ,  1700 A 5 - 1700   n   5  are excited ( FIG.  51   , Block  5100 ) in the manner described above with respect to  FIG.  42   , Block  4230  and/or  FIG.  43   , Block  4330  so that the base  1510  of the wafer handler  1500 - 1500 B is levitated. With the base  1510  of the wafer handler  1500 - 1500 B levitated, vibrations induced in the base  1510  from the levitation are compensated for ( FIG.  51   , Block  5110 ), as described above with respect to any one or more of  FIGS.  47 A- 48 C  (see also  FIG.  42   , Block  4260  and  FIG.  43   , Block  4360 ) so that the end effector  1520  and any substrate S held thereon are substantially free of vibrations. The wafer handler  1500 - 1500 B is moved along one or more transport paths (as described herein) so as to pick one or more substrates S from any suitable substrate holding station(s) described herein ( FIG.  51   , Block  5120 ). The wafer handler  1500 - 1500 B is moved along the one or more transport paths to position the substrate S for placement at the same or a different substrate holding station ( FIG.  51   , Block  5130 ). Placement of the substrates may be effected with the wafer handler  1500 - 1500 B being configured with a single end effector  1520  (see, e.g., for exemplary purposes only, at least  FIG.  1 A ), a double sided/ended end effector  1520  (see, see, e.g., for exemplary purposes only, at least  FIGS.  13 A and  16 A- 16 C ), or with multiple end effectors  1520 A,  1520 B (see, e.g., for exemplary purposes only, at least  FIGS.  10 A- 11 A ). As described herein, the temperature of the base  1510  may be monitored in any suitable manner (e.g., such as with wireless temperature sensors mounted on the base  1510 , optical temperature sensors positioned to detect the base  1510  temperature as the wafer handler  1500 - 1500 B moves through a transport chamber, etc.) so as to effect temperature control of the base  1510  ( FIG.  51   , Block  5140 ) of the wafer handler  1500 - 1500 B in the manner described above with respect to  FIG.  46    (see also  FIG.  42   , Block  4250  and/or  FIG.  43   , Block  4350 ). Temperature control of the base  1510  may be effected when the wafer handler  1500 - 1500 B is idle (e.g., not holding a substrate such as between wafer transfers or during a fast swapping of substrates), or in other aspects with the wafer handler  1500 - 1500 B holding a substrate. 
     In accordance with one or more aspects of the disclosed embodiment a linear electrical machine comprises: a frame with a level reference plane; an array of electromagnets, connected to the frame to form a drive plane at a predetermined height relative to the level reference plane, the array of electromagnets being arranged so that a series of electromagnets of the array of electromagnets define at least one drive line within the drive plane, and each of the electromagnets being coupled to an alternating current power source energizing each electromagnet; at least one reaction platen of paramagnetic, diamagnetic, or non-magnetic conductive material disposed to cooperate with the electromagnets of the array of electromagnets so that excitation of the electromagnets with alternating current generates levitation and propulsion forces against the reaction platen that controllably levitate and propel the reaction platen along the at least one drive line, in a controlled attitude relative to the drive plane; and a controller operably coupled to the array of electromagnets and the alternating current power source and configured so as to sequentially excite the electromagnets with multiphase alternating current with a predetermined excitation characteristic so that each reaction platen is levitated and propelled with up to six degrees of freedom, wherein the controller is configured so as to determine reaction platen position feedback, in at least one degree of freedom from the up to six degrees of freedom, from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet effecting levitation or propulsion of the reaction platen, wherein the variance in the predetermined excitation characteristic defines self-deterministic reaction platen position feedback of each of the at least one electromagnet, of the array of electromagnets, effecting levitation or propulsion of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the six degrees of freedom include at least one of attitude control and yaw control, the at least one of the attitude control and the yaw control are effected with a common set of electromagnets of the array of electromagnets, where each electromagnet generates, from excitation with common multiphase alternating current having a single common frequency per phase, both the levitation and the propulsion forces against the reaction platen so as to control the reaction platen with the up to six degrees of freedom including at least one of reaction platen attitude and reaction platen yaw at least with the reaction platen levitated. 
     In accordance with one or more aspects of the disclosed embodiment the self-deterministic reaction platen position feedback is an absolute position feedback. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined excitation characteristic is one or more of inductance, a power factor, an impedance, and a lag between voltage and current of the multiphase alternating current. 
     In accordance with one or more aspects of the disclosed embodiment the at least one reaction platen comprises more than one reaction platen, each of the more than one reaction platen having a corresponding shape that defines a respective power factor signature; and the controller is configured to determine a position of each reaction platen based on the respective power factor signature. 
     In accordance with one or more aspects of the disclosed embodiment a frequency is superimposed on a fundamental frequency of a voltage generated by the alternating current power source, the frequency being separate and distinct from the fundamental frequency so as to decouple position feedback determination from levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude with the reaction platen levitated and propelled so as to move relative to the array of electromagnets along the at least one drive line from a first predetermined position with respect to the frame to a second different predetermined position with respect to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude and the reaction platen yaw with the reaction platen levitated and stationary relative to the array of electromagnets in a predetermined position along the at least one drive line with respect to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the propulsion forces, generated by the array of electromagnets, across the reaction platen so as to impart a controlled yaw moment on the reaction platen, yawing the reaction platen about a yaw axis, substantially normal to the drive plane, from a first predetermined orientation relative to the frame, to a second different predetermined orientation relative to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the propulsion forces, generated by the array of electromagnets, so as to impart a moment couple on the reaction platen effecting controlled yaw of the reaction platen so as to effect at least one of positioning and centering of a wafer payload on the reaction platen relative to a predetermined wafer holding location of the frame. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the levitation forces, generated by the array of electromagnets, so as to impart differential levitation forces across the reaction platen that effect a controlled inclination of the reaction platen, relative to the drive plane, that controls a predetermined reaction platen attitude in at least one of reaction platen pitch and reaction platen roll. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the levitation forces, generated by the array of electromagnets, so as to effect a predetermined bias attitude of the reaction platen, relative to the drive plane, that imparts a bias reaction force, from a reaction platen payload seating surface on a payload supported by the reaction platen seating surface, in a direction countering payload inertial force arising from acceleration of the reaction platen along the drive plane. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured to determine acceleration of the reaction platen along the drive plane at least from the variance in the predetermined excitation characteristic, and in response to the acceleration determined, control a bias attitude of the reaction platen to provide the predetermined bias attitude countering the payload inertial force arising from the acceleration of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls excitation of the electromagnets of the array of electromagnets so as to set the reaction platen attitude to bias the reaction platen against inertial forces tending to displace a payload, seated against the reaction platen, relative to the reaction platen along a seat between the payload and the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured with a predetermined reaction platen temperature management protocol effecting temperature control of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined reaction platen temperature management protocol controls a temperature of the at least one reaction platen via conduction from the at least one reaction platen to a thermal sink commensurate at least with a wafer swap operation of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the linear electrical machine further includes at least another reaction platen, that is alternate to the at least one reaction platen, and held inactive so as to be in a cold state, relative to the at least one reaction platen in its operative state, and the predetermined reaction platen temperature management protocol includes the at least another reaction platen being switched to an operative state and replacing the at least one reaction platen, at its temperature limit, with the at least another reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the linear electrical machine further includes a passive vibration compensator having a natural frequency mode tuned to compensate for vibration of the at least one reaction platen under levitation propulsion forces so as to effect a substantially vibration free end effector with respect to the end effector natural vibration frequency modes, wherein the at least one reaction platen includes a respective end effector. 
     In accordance with one or more aspects of the disclosed embodiment an electromagnetic conveyor substrate transport apparatus comprises: a chamber configured to hold a sealed atmosphere therein, and having a level reference plane and at least one substrate pass through opening for transferring a substrate in and out of the chamber through the opening; an array of electromagnets, connected to the chamber to form a drive plane at a predetermined height relative to the level reference plane, the array of electromagnets being arranged so that a series of electromagnets of the array of electromagnets define at least one drive line within the drive plane, electromagnets in the series of electromagnets being grouped into at least one multiphase actuator unit, and each of the at least one multiphase actuator unit being coupled to a multiphase alternating current power source; at least one reaction platen of paramagnetic, diamagnetic, or non-magnetic conductive material disposed to cooperate with the electromagnets of the at least one multiphase actuator unit so that excitation of the electromagnets with alternating current generates levitation and propulsion forces against the reaction platen that controllably levitate and propel the reaction platen along the at least one drive line, in a controlled attitude relative to the drive plane; and a controller operably coupled to the array of electromagnets and alternating current power source and configured so as to sequentially excite the electromagnets with multiphase alternating current with a predetermined excitation characteristic so that the at least one reaction platen is levitated and propelled, wherein the controller is configured so as to determine reaction platen position feedback from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen, wherein the variance in the predetermined characteristic defines self-deterministic reaction platen position feedback of each of the electromagnets of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment each alternating current phase, of the multiphase alternating current, is dynamically allocated between respective electromagnets so that the alternating current phase of each respective electromagnet, of the electromagnet group of the at least one multiphase actuator unit, changes from a first alternating current phase to a second different alternating current phase so in effect the electromagnet group moves virtually and the at least one multiphase actuator unit formed by the electromagnet group moves virtually via dynamic phase allocation along the drive line. 
     In accordance with one or more aspects of the disclosed embodiment the self-deterministic reaction platen position feedback is an absolute position feedback. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined excitation characteristic is one or more of inductance, a power factor, an impedance, and a lag between voltage and current of the multiphase alternating current. 
     In accordance with one or more aspects of the disclosed embodiment the at least one reaction platen comprises more than one reaction platen, each of the more than one reaction platen having a corresponding shape that defines a respective power factor signature; and the controller is configured to determine a position of each reaction platen based on the respective power factor signature. 
     In accordance with one or more aspects of the disclosed embodiment a frequency is superimposed on a fundamental frequency of a voltage generated by the multiphase alternating current power source, the frequency being separate and distinct from the fundamental frequency so as to decouple position feedback determination from levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the reaction platen is levitated and propelled with up to six degrees of freedom including at least one of attitude and yaw control with the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude with the reaction platen levitated and propelled so as to move relative to the array of electromagnets along the at least one drive line from a first predetermined position with respect to the chamber to a second different predetermined position with respect to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude and the reaction platen yaw with the reaction platen levitated and stationary relative to the array of electromagnets in a predetermined position along the at least one drive line with respect to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the dynamic phase allocation is controlled so that the virtually moving at least one multiphase actuator unit moves virtually along the drive line substantially coincident with reaction platen movement along the drive line from propulsion by the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the propulsion forces, generated by the array of electromagnets, across the reaction platen so as to impart a controlled yaw moment on the reaction platen, yawing the reaction platen about a yaw axis, substantially normal to the drive plane, from a first predetermined orientation relative to the chamber, to a second different predetermined orientation relative to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the propulsion forces, generated by the array of electromagnets, so as to impart a moment couple on the reaction platen effecting controlled yaw of the reaction platen so as to effect at least one of positioning and centering of a wafer payload on the reaction platen relative to a predetermined wafer holding location of the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the levitation forces, generated by the array of electromagnets, so as to impart differential levitation forces across the reaction platen that effect a controlled inclination of the reaction platen, relative to the drive plane, that controls a predetermined reaction platen attitude in at least one of reaction platen pitch and reaction platen roll. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls the levitation forces, generated by the array of electromagnets, so as to effect a predetermined bias attitude of the reaction platen, relative to the drive plane, that imparts a bias reaction force, from a reaction platen payload seating surface on a payload supported by the reaction platen seating surface, in a direction countering payload inertial force arising from acceleration of the reaction platen along the drive plane. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured to determine acceleration of the reaction platen along the drive plane at least from the variance in the predetermined excitation characteristic, and in response to the acceleration determined, control a bias attitude of the reaction platen to provide the predetermined bias attitude countering the payload inertial force arising from the acceleration of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the controller controls excitation of the electromagnets of the array of electromagnets so as to set the reaction platen attitude to bias the reaction platen against inertial forces tending to displace a payload, seated against the reaction platen, relative to the reaction platen along a seat between the payload and the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the dynamic phase allocation is controlled so that the respective electromagnets energized by the multiphase alternating current present, with respect to the reaction platen, a substantially steady state multiphase distribution across respective electromagnets of the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured with a predetermined reaction platen temperature management protocol effecting temperature control of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined reaction platen temperature management protocol controls a temperature of the at least one reaction platen via conduction from the at least one reaction platen to a thermal sink commensurate at least with a wafer swap operation of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the linear electrical machine further includes at least another reaction platen, that is alternate to the at least one reaction platen, and held inactive so as to be in a cold state, relative to the at least one reaction platen in its operative state, and the predetermined reaction platen temperature management protocol includes the at least another reaction platen being switched to an operative state and replacing the at least one reaction platen, at its temperature limit, with the at least another reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the linear electrical machine further includes a passive vibration compensator having a natural frequency mode tuned to compensate for vibration of the at least one reaction platen under levitation propulsion forces so as to effect a substantially vibration free end effector with respect to the end effector natural vibration frequency modes, wherein the at least one reaction platen includes a respective end effector. 
     In accordance with one or more aspects of the disclosed embodiment a method for a linear electrical machine is provided. The method comprises: providing the linear electrical machine with a frame having a level reference plane; forming a drive plane, with an array of electromagnets connected to the frame, at a predetermined height relative to the level reference plane, the array of electromagnets being arranged so that a series of electromagnets of the array of electromagnets define at least one drive line within the drive plane, and each of the electromagnets being coupled to an alternating current power source energizing each electromagnet; providing at least one reaction platen of paramagnetic, diamagnetic, or non-magnetic conductive material disposed to cooperate with the electromagnets of the array of electromagnets; exciting the electromagnets with alternating current to generate levitation and propulsion forces against the reaction platen that controllably levitate and propel the reaction platen along the at least one drive line, in a controlled attitude relative to the drive plane where the electromagnets are sequentially excited, with a controller operably coupled to the array of electromagnets and the alternating current power source, with multiphase alternating current with a predetermined excitation characteristic so that each reaction platen is levitated and propelled with up to six degrees of freedom; and determining, with the controller, reaction platen position feedback, in at least one degree of freedom from the up to six degrees of freedom, from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet effecting levitation or propulsion of the reaction platen, wherein the variance in the predetermined characteristic defines self-deterministic reaction platen position feedback of each of the at least one electromagnet, of the array of electromagnets, effecting levitation or propulsion of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the six degrees of freedom include at least one of attitude control and yaw control, the at least one of the attitude control and the yaw control are effected with a common set of electromagnets of the array of electromagnets, where each electromagnet generates, from excitation with common multiphase alternating current having a single common frequency per phase, both the levitation and the propulsion forces against the reaction platen so as to control the reaction platen with the up to six degrees of freedom including at least one of reaction platen attitude and reaction platen yaw at least with the reaction platen levitated. 
     In accordance with one or more aspects of the disclosed embodiment the self-deterministic reaction platen position feedback is an absolute position feedback. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined excitation characteristic is one or more of inductance, a power factor, an impedance, and a lag between voltage and current of the multiphase alternating current. 
     In accordance with one or more aspects of the disclosed embodiment the at least one reaction platen comprises more than one reaction platen and each of the more than one reaction platen has a corresponding shape that defines a respective power factor signature, the method further comprises: determining, with the controller, a position of each reaction platen based on the respective power factor signature. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: superimposing a frequency on a fundamental frequency of a voltage generated by the alternating current power source, the frequency being separate and distinct from the fundamental frequency so as to decouple position feedback determination from levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude with the reaction platen levitated and propelled so as to move relative to the array of electromagnets along the at least one drive line from a first predetermined position with respect to the frame to a second different predetermined position with respect to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude and the reaction platen yaw with the reaction platen levitated and stationary relative to the array of electromagnets in a predetermined position along the at least one drive line with respect to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the propulsion forces, generated by the array of electromagnets, across the reaction platen so as to impart a controlled yaw moment on the reaction platen, yawing the reaction platen about a yaw axis, substantially normal to the drive plane, from a first predetermined orientation relative to the frame, to a second different predetermined orientation relative to the frame. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the propulsion forces, generated by the array of electromagnets, so as to impart a moment couple on the reaction platen effecting controlled yaw of the reaction platen so as to effect at least one of positioning and centering of a wafer payload on the reaction platen relative to a predetermined wafer holding location of the frame. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the levitation forces, generated by the array of electromagnets, so as to impart differential levitation forces across the reaction platen that effect a controlled inclination of the reaction platen, relative to the drive plane, that controls a predetermined reaction platen attitude in at least one of reaction platen pitch and reaction platen roll. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the levitation forces, generated by the array of electromagnets, so as to effect a predetermined bias attitude of the reaction platen, relative to the drive plane, that imparts a bias reaction force, from a reaction platen payload seating surface on a payload supported by the reaction platen seating surface, in a direction countering payload inertial force arising from acceleration of the reaction platen along the drive plane. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: determining, with the controller, acceleration of the reaction platen along the drive plane at least from the variance in the predetermined excitation characteristic, and in response to the acceleration determined, control a bias attitude of the reaction platen to provide the predetermined bias attitude countering the payload inertial force arising from the acceleration of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, excitation of the electromagnets of the array of electromagnets so as to set the reaction platen attitude to bias the reaction platen against inertial forces tending to displace a payload, seated against the reaction platen, relative to the reaction platen along a seat between the payload and the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured with a predetermined reaction platen temperature management protocol effecting temperature control of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined reaction platen temperature management protocol controls a temperature of the at least one reaction platen via conduction from the at least one reaction platen to a thermal sink commensurate at least with a wafer swap operation of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment at least another reaction platen, that is alternate to the at least one reaction platen, is held inactive so as to be in a cold state, relative to the at least one reaction platen in its operative state, and the predetermined reaction platen temperature management protocol includes switching the at least another reaction platen to an operative state and replacing the at least one reaction platen, at its temperature limit, with the at least another reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the method further includes compensating for vibration of the at least one reaction platen under levitation propulsion forces with a passive vibration compensator, having a natural frequency mode tuned to compensate for the vibration of the at least one reaction platen, so as to effect a substantially vibration free end effector with respect to the end effector natural vibration frequency modes, wherein the at least one reaction platen includes a respective end effector. 
     In accordance with one or more aspects of the disclosed embodiment a method for an electromagnetic conveyor substrate transport apparatus is provided. The method comprises: providing the electromagnetic conveyor substrate transport apparatus with a chamber configured to hold a sealed atmosphere therein, and having a level reference plane and at least one substrate pass through opening for transferring a substrate in and out of the chamber through the opening; forming a drive plane with an array of electromagnets connected to the chamber at a predetermined height relative to the level reference plane, the array of electromagnets being arranged so that a series of electromagnets of the array of electromagnets define at least one drive line within the drive plane, electromagnets in the series of electromagnets being grouped into at least one multiphase actuator unit, and each of the at least one multiphase actuator unit being coupled to a multiphase alternating current power source; providing at least one reaction platen of paramagnetic, diamagnetic, or non-magnetic conductive material disposed to cooperate with the electromagnets of the at least one multiphase actuator unit; exciting the electromagnets with alternating current to generate levitation and propulsion forces against the reaction platen that controllably levitate and propel the reaction platen along the at least one drive line, in a controlled attitude relative to the drive plane, where the electromagnets are sequentially excited, with a controller operably coupled to the array of electromagnets and alternating current power source, with multiphase alternating current with a predetermined excitation characteristic so that the at least one reaction platen is levitated and propelled; and determining, with the controller, reaction platen position feedback from variance in the predetermined excitation characteristic of the alternating current of at least one electromagnet of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen, wherein the variance in the predetermined characteristic defines self-deterministic reaction platen position feedback of each of the electromagnets of the at least one multiphase actuator unit effecting levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment each alternating current phase, of the multiphase alternating current, is dynamically allocated between respective electromagnets so that the alternating current phase of each respective electromagnet, of the electromagnet group of the at least one multiphase actuator unit, changes from a first alternating current phase to a second different alternating current phase so in effect the electromagnet group moves virtually and the at least one multiphase actuator unit formed by the electromagnet group moves virtually via dynamic phase allocation along the drive line. 
     In accordance with one or more aspects of the disclosed embodiment the self-deterministic reaction platen position feedback is an absolute position feedback. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined excitation characteristic is one or more of an inductance, a power factor and, a lag between voltage and current of the multiphase alternating current. 
     In accordance with one or more aspects of the disclosed embodiment the at least one reaction platen comprises more than one reaction platen, each of the more than one reaction platen having a corresponding shape that defines a respective power factor signature, the method further comprises: determining, with the controller, a position of each reaction platen based on the respective power factor signature. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: superimposing a frequency on a fundamental frequency of a voltage generated by the multiphase alternating current power source, the frequency being separate and distinct from the fundamental frequency so as to decouple position feedback determination from levitation and propulsion of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the reaction platen is levitated and propelled with up to six degrees of freedom including at least one of attitude and yaw control with the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling with the controller, the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude with the reaction platen levitated and propelled so as to move relative to the array of electromagnets along the at least one drive line from a first predetermined position with respect to the chamber to a second different predetermined position with respect to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the up to six degrees of freedom, generated by the array of electromagnets, including at least the reaction platen attitude and the reaction platen yaw with the reaction platen levitated and stationary relative to the array of electromagnets in a predetermined position along the at least one drive line with respect to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling the dynamic phase allocation so that the virtually moving at least one multiphase actuator unit moves virtually along the drive line substantially coincident with reaction platen movement along the drive line from propulsion by the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the propulsion forces, generated by the array of electromagnets, across the reaction platen so as to impart a controlled yaw moment on the reaction platen, yawing the reaction platen about a yaw axis, substantially normal to the drive plane, from a first predetermined orientation relative to the chamber, to a second different predetermined orientation relative to the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the propulsion forces, generated by the array of electromagnets, so as to impart a moment couple on the reaction platen effecting controlled yaw of the reaction platen so as to effect at least one of positioning and centering of a wafer payload on the reaction platen relative to a predetermined wafer holding location of the chamber. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the levitation forces, generated by the array of electromagnets, so as to impart differential levitation forces across the reaction platen that effect a controlled inclination of the reaction platen, relative to the drive plane, that controls a predetermined reaction platen attitude in at least one of reaction platen pitch and reaction platen roll. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, the levitation forces, generated by the array of electromagnets, so as to effect a predetermined bias attitude of the reaction platen, relative to the drive plane, that imparts a bias reaction force, from a reaction platen payload seating surface on a payload supported by the reaction platen seating surface, in a direction countering payload inertial force arising from acceleration of the reaction platen along the drive plane. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: determining, with the controller, acceleration of the reaction platen along the drive plane at least from the variance in the predetermined excitation characteristic, and in response to the acceleration determined, control a bias attitude of the reaction platen to provide the predetermined bias attitude countering the payload inertial force arising from the acceleration of the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the method further comprises: controlling, with the controller, excitation of the electromagnets of the array of electromagnets so as to set the reaction platen attitude to bias the reaction platen against inertial forces tending to displace a payload, seated against the reaction platen, relative to the reaction platen along a seat between the payload and the reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the dynamic phase allocation is controlled so that the respective electromagnets energized by the multiphase alternating current present, with respect to the reaction platen, a substantially steady state multiphase distribution across respective electromagnets of the virtually moving at least one multiphase actuator unit. 
     In accordance with one or more aspects of the disclosed embodiment the controller is configured with a predetermined reaction platen temperature management protocol effecting temperature control of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment the predetermined reaction platen temperature management protocol controls a temperature of the at least one reaction platen via conduction from the at least one reaction platen to a thermal sink commensurate at least with a wafer swap operation of the at least one reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment at least another reaction platen, that is alternate to the at least one reaction platen, is held inactive so as to be in a cold state, relative to the at least one reaction platen in its operative state, and the predetermined reaction platen temperature management protocol includes switching the at least another reaction platen to an operative state and replacing the at least one reaction platen, at its temperature limit, with the at least another reaction platen. 
     In accordance with one or more aspects of the disclosed embodiment method further includes compensating for vibration of the at least one reaction platen under levitation propulsion forces with a passive vibration compensator, having a natural frequency mode tuned to compensate for the vibration of the at least one reaction platen, so as to effect a substantially vibration free end effector with respect to the end effector natural vibration frequency modes, wherein the at least one reaction platen includes a respective end effector. 
     It should be understood that the foregoing description is only illustrative of the aspects of the disclosed embodiment. Various alternatives and modifications can be devised by those skilled in the art without departing from the aspects of the disclosed embodiment. Accordingly, the aspects of the disclosed embodiment are intended to embrace all such alternatives, modifications and variances that fall within the scope of any claims appended hereto. Further, the mere fact that different features are recited in mutually different dependent or independent claims does not indicate that a combination of these features cannot be advantageously used, such a combination remaining within the scope of the aspects of the present disclosure.