Patent Publication Number: US-2015075751-A1

Title: Fluid distribution network for large stator motor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority on U.S. Provisional Application Ser. No. 61/878,517 filed on Sep. 16, 2013 and entitled “FLUID DISTRIBUTION NETWORK FOR LARGE STATOR MOTOR”. As far as is permitted, the contents of U.S. Provisional Application Ser. No. 61/878,517 are incorporated herein by reference. 
    
    
     BACKGROUND 
     Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage assembly that retains a reticle, a lens assembly and a wafer stage assembly that retains a semiconductor wafer. Typically, the wafer stage assembly includes a wafer stage base, a wafer stage that retains the wafer, and a wafer stage mover assembly that precisely positions the wafer stage and the wafer. Somewhat similarly, the reticle stage assembly includes a reticle stage base, a reticle stage that retains the reticle, and a reticle stage mover assembly that precisely positions the reticle stage and the reticle. The size of the images and the features within the images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise relative positioning of the wafer and the reticle is critical to the manufacturing of high density, semiconductor wafers. 
     Unfortunately, the stage mover assemblies generate heat that can influence the other components of the exposure apparatus. Conventionally, the stage mover assemblies are cooled by forcing a coolant around the movers of the stage mover assembly. However, existing coolant systems do not adequately or efficiently cool the movers of the stage mover assembly. Additionally, existing coolant systems do not adequately or efficiently inhibit pressure loss, i.e. pressure drops, or thermal deformation within the stage mover assembly. This can reduce the accuracy of positioning of the wafer relative to the reticle, and degrade the accuracy of the exposure apparatus. 
     SUMMARY 
     The present invention is directed to a reaction assembly for supporting a mover relative to a base. In certain embodiments, the reaction assembly comprises a countermass assembly and a fluid distribution network. The countermass supports a portion of the mover. Additionally, the fluid distribution network allows for circulating a fluid to provide cooling for the portion of the mover. The fluid distribution network is positioned substantially adjacent to the countermass assembly, the fluid distribution network is substantially decoupled from the structure of the countermass assembly to inhibit thermal deformation of the countermass. Further, the fluid distribution network can be designed to inhibit pressure drops within the fluid distribution network. 
     In some embodiments, the countermass assembly includes a distribution plate assembly. In such embodiments, a majority of the fluid distribution network is positioned below and substantially adjacent to a bottom surface of the distribution plate assembly. Additionally, the distribution plate assembly can include a plurality of unit apertures, each unit aperture being adapted to receive one of a plurality of coil units. In one embodiment, the fluid distribution network is adapted to supply circulation fluid to the coil units to cool the coil units. Moreover, in one embodiment, the fluid distribution network includes a Coil Temperature Control network for cooling individual coils within the coil units, and a Surface Temperature Control network for cooling a surface of the coil units. 
     The present invention is further directed toward a stage assembly including a stage base, a stage that retains a device, a stage mover that moves the stage relative to the stage base, and the reaction assembly as described above that supports a portion of the stage mover. In one embodiment, the stage mover includes a conductor array having a plurality of coil units, and the fluid distribution network provides cooling for the coil units. Additionally, the present invention is further directed toward an exposure apparatus including the stage assembly as described above that retains the device, and an illumination source that guides a beam of light energy toward the device; and a process for manufacturing a wafer that includes the steps of providing a substrate, and transferring a mask pattern to the substrate with the exposure apparatus. 
     In another application, the present invention is also directed toward a reaction assembly for supporting a mover relative to a base, the reaction assembly comprising (i) a countermass assembly that supports a portion of the mover, the countermass assembly including a distribution plate assembly; and (ii) a fluid distribution network that cools the portion of the mover, a majority of the fluid distribution network being positioned below and substantially adjacent to a bottom surface of the distribution plate assembly. 
     In still another application, the present invention is further directed toward a reaction assembly for supporting a mover relative to a base, the reaction assembly comprising (i) a distribution plate assembly that supports a portion of the mover including a plurality of passageways; and (ii) a fluid distribution network including a fluid source that provides a circulation fluid that cools the portion of the mover, wherein the passageways extend between the fluid distribution network and the portion of the mover, the passageways providing the only source of the circulation fluid within the distribution plate assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is a perspective view of an embodiment of a stage assembly having features of the present invention; 
         FIG. 2A  is a simplified view of a coil unit, a portion of a distribution plate assembly, and a portion of a fluid distribution network having features of the present invention; 
         FIG. 2B  is a perspective view of the coil unit of  FIG. 2A ; 
         FIG. 3A  is a top plan view of the distribution plate assembly of  FIG. 2A ; 
         FIG. 3B  is a top plan view of a portion of the distribution plate assembly of  FIG. 3A ; 
         FIG. 3C  is a bottom plan view of the portion of the distribution plate assembly of  FIG. 3B ; 
         FIG. 3D  is a cut-away view taken on line  3 D- 3 D in  FIG. 3C ; 
         FIG. 4A  is a simplified bottom view of the distribution plate assembly and a portion of the fluid distribution network; 
         FIG. 4B  is a bottom view of the portion of the fluid distribution network of  FIG. 4A ; 
         FIG. 4C  is a top view of the portion of the fluid distribution network of  FIG. 4A ; 
         FIG. 4D  is a cutaway perspective view taken from  FIG. 4C ; 
         FIG. 5A  is a bottom perspective view of a portion of the fluid distribution network; 
         FIG. 5B  is a bottom view of the portion of the fluid distribution network of  FIG. 5A ; 
         FIG. 6A  is a bottom perspective view of a distribution conduit array; 
         FIG. 6B  is a top view of the portion of the distribution conduit array of  FIG. 6A ; 
         FIG. 6C  is an inverted side view of the distribution conduit array; 
         FIG. 7A  is a bottom perspective view of a portion of the fluid distribution network; 
         FIG. 7B  is a bottom view of the portion of the fluid distribution network of  FIG. 7A ; 
         FIG. 8A  is a perspective view of a connector that can be used to connect a portion of the fluid distribution network to the distribution plate; 
         FIG. 8B  is a perspective view of a portion of the distribution plate and the connector of  FIG. 8A ; 
         FIG. 9  is a schematic illustration of an exposure apparatus having features of the present invention; 
         FIG. 10A  is a flow chart that outlines a process for manufacturing a device in accordance with the present invention; and 
         FIG. 10B  is a flow chart that outlines device processing in more detail. 
     
    
    
     DESCRIPTION 
       FIG. 1  is a perspective view of an embodiment of a stage assembly  10  having features of the present invention. As illustrated in this embodiment, the stage assembly  10  includes a stage base  12 , a stage  14  that retains a device  16 , a stage mover  18 , a countermass reaction assembly  20  (also referred to herein simply as a “reaction assembly”), and a control system  22 . The design of each of these components can be varied to suit the design requirements of the stage assembly  10 . In certain applications, the stage assembly  10  can be positioned above a mounting base  24  (illustrated in  FIG. 9 ). The stage mover  18  precisely moves the stage  14  and the device  16  relative to the stage base  12  and the reaction assembly  20 . 
     As an overview, in certain embodiments, the reaction assembly  20  includes (i) a countermass assembly  26  that supports a portion of the stage mover  18 , and (ii) a fluid distribution network  28  that effectively and efficiently controls the flow of fluid in and around the stage mover  18  and the reaction assembly  20 . More particularly, the fluid distribution network  28  is designed to inhibit undesired pressure drops while distributing a large volume of fluid over a relatively large area of the stage assembly  10 . Additionally, the fluid distribution network  28  is designed to be substantially decoupled from the physical structure of the countermass assembly  26  to more effectively manage the thermal strain that may otherwise exist within the stage assembly  10 , e.g., within the stage mover  18 . 
     Further, the fluid distribution network  28  directs a circulation fluid  30  (illustrated with small circles) to a portion of the stage mover  18  and the countermass assembly  26  to control the temperature around the stage mover  18  and reaction assembly  20 . In one embodiment, the fluid distribution network  28  includes (i) a body fluid source  32  that circulates the circulation fluid  30  to primarily remove the heat from the stage mover  18  and the countermass assembly  26 ; and (ii) a surface fluid source  32  that circulates the circulation fluid  30  to control the temperature of the upper surface of a portion of the stage mover  18  to inhibit the transfer of heat from the stage mover  18  to the surrounding environment. It should be noted that either of the fluid sources  32 ,  34  can be referred to as a first fluid source or a second fluid source. 
     In  FIG. 1 , each fluid source  32 ,  34  is illustrated as including a single source outlet  35 A, and a single source inlet  35 B. Alternatively, each fluid source  32 ,  34  can include multiple source outlets and source inlets. Further, the fluid sources  32 ,  34  can be combined into a single system or more than two systems. Moreover, each fluid source  32 ,  34  can include one or more pumps, reservoirs, flow regulators, pressure regulators, valves, temperature controllers, chillers, and/or heaters to precisely control the temperature and flow rate of the fluid  30 . 
     In certain embodiments, the body fluid source  32  independently controls the flow rate of the circulation fluid  30  to different areas of the stage mover  18  so that more circulation fluid  30  can be directed to the areas of the stage mover  18  that are used the most and that are generating the most heat, and less is directed to the areas that are used the least and that are generating less heat. Moreover, in certain embodiments, the circulation fluid  30  can be provided at a high flow rate to a large area of the stage mover  18  while inhibiting thermal deformation and providing a manufacturable design by using a modular design to create a fluid flow network wherein the circulation fluid  30  flows primarily in non-structural parts, and wherein the fluid distribution network  28  is configured in a hierarchical (tree) manner. This will allow for the efficient cooling of the stage mover  18 . Still further, the fluid distribution network  28  can efficiently and accurately maintain a substantially uniform temperature of the stage mover  18  and the reaction assembly  20 , which, in turn, allows for more accurate positioning of the stage  14  and the device  16 . 
     The stage assembly  10  is particularly useful for precisely positioning the device  16  during a manufacturing and/or an inspection process. The type of device  16  positioned and moved by the stage assembly  10  can be varied. For example, the device  16  can be a semiconductor wafer, and the stage assembly  10  can be used as part of an exposure apparatus for precisely positioning the semiconductor wafer during manufacturing of the semiconductor wafer. Alternatively, for example, the stage assembly  10  can be used to move other types of devices during manufacturing and/or inspection, to move a device under an electron microscope (not shown), or to move a device during a precision measurement operation (not shown). 
     Some of the Figures provided herein include an orientation system that designates an X axis, a Y axis, and a Z axis. It should be understood that the orientation system is merely for reference and can be varied. For example, the X axis can be switched with the Y axis and/or the stage assembly  10  can be rotated. Moreover, these axes can alternatively be referred to as a first, second, or third axis. 
     The stage base  12  supports a portion of the stage assembly  10  above the mounting base  24 . In the embodiment illustrated herein, the stage base  12  is rigid and generally rectangular shaped. 
     As noted above, the stage  14  retains the device  16 . Further, the stage  14  is precisely moved by the stage mover  18  to precisely position the device  16 . In the embodiments illustrated herein, the stage  14  is generally rectangular shaped and includes a device holder (not shown) for retaining the device  16 . The device holder can be a vacuum chuck, an electrostatic chuck, or some other type of clamp. 
     The stage  14  can be maintained spaced apart from (e.g., above) the reaction assembly  20  with the stage mover  18  if the stage mover  18  is a six degree of freedom mover that moves the stage  14  relative to the reaction assembly  20  with six degrees of freedom. In this embodiment, the stage mover  18  functions as a magnetic type bearing that levitates the stage  14 . Alternatively, for example, the stage  14  can be supported relative to the reaction assembly  20  with a stage bearing (not shown), e.g., a vacuum preload type fluid bearing. For example, the bottom of the stage  14  can include a plurality of spaced apart fluid outlets (not shown), and a plurality of spaced apart fluid inlets (not shown). In this example, pressurized fluid (not shown) can be released from the fluid outlets towards the reaction assembly  20  and a vacuum can be pulled in the fluid inlets to create a vacuum preload type, fluid bearing between the stage  14  and the reaction assembly  20 . In this embodiment, the stage bearing allows for motion of the stage  14  relative to the reaction assembly  20  along the X axis, along the Y axis and about the Z axis. 
     The stage mover  18  controls and adjusts the position of the stage  14  and the device  16  relative to the reaction assembly  20  and the stage base  12 . For example, the stage mover  18  can be a planar motor that moves and positions the stage  14  along the X axis, along the Y axis and about the Z axis (“three degrees of freedom” or “the planar degrees of freedom”). Further, in certain embodiments, the stage mover  18  can also be controlled to move the stage  14  along Z axis and about the X and Y axes. With this design, the stage mover  18  is a six degree of freedom mover. Alternatively, in certain embodiments, the stage mover  18  can be another type of actuator designed to move the stage  14  with less than six degrees of freedom. 
     In the embodiments illustrated herein, the stage mover  16  includes a conductor array  36 , and an adjacent magnet array  38  that interacts with the conductor array  36 . In  FIG. 1 , the conductor array  36  is coupled to the reaction assembly  20 , and the magnet array  38  is secured to the stage  14 . Alternatively, in one embodiment, the conductor array  36  can be coupled to the stage  14  and the magnet array  38  can be coupled to the reaction assembly  20 . As provided herein, the array secured to the stage  14  can be referred to as the moving component of the stage mover  18 , and the array secured to the reaction assembly  20  can be referred to as the reaction component (or stator) of the stage mover  18 . 
     In one embodiment, the conductor array  36  can include a plurality of coil units  40 , and each coil unit  40  can include a single coil (not shown) that is oriented to provide movement along the X-axis or the Y-axis. Alternatively, each coil unit  40  can include more than one coil (e.g. three coils). Still alternatively, each coil unit  40  can include one of more coils that is oriented to provide movement along the X-axis, and one or more coils that is oriented to provide movement along the Y-axis. Each coil can be made of a metal such as copper or any substance or material responsive to electrical current and capable of creating a magnetic field such as superconductors. 
     The design and number of coil units  40  in the conductor array  36  can vary according to the performance and movement requirements of the stage mover  18 . For example, in the embodiment illustrated in  FIG. 1 , the conductor array  36  includes two hundred sixty-four coil units  40  that are arranged in a generally rectangular twelve by twenty-two array. Additionally, the individual coil units  40  can be arranged such that a plurality of Y-coil units and a plurality of X-coil units are positioned and/or arranged in an alternating pattern in both the X-direction and the Y-direction. Thus, in such embodiment, the conductor array  36  includes one hundred thirty-two X-coil units  40  and one hundred thirty-two Y-coil units  40  that are arranged in an alternating pattern in both the X-direction and the Y-direction. 
     Further, the magnet array  38  can include one or more magnets (not illustrated) that interact with the plurality of coil units  40 . The design of the magnet array  38  and the number of magnets in the magnet array  38  can be varied to suit the design requirements of the stage mover  18 . In some embodiments, each magnet can be made of a permanent magnetic material such as NdFeB. 
     Electrical current (not shown) is supplied to the coil units  40  by the control system  22 . The electrical current in the coil units  40  interacts with the magnetic field(s) of the one or more magnets in the magnet array  38 . This causes a force (Lorentz type force) between the coil units  40  and the magnets that can be used to move the stage  14  relative to the stage base  12 . 
     Unfortunately, the electrical current supplied to the coil units  40  also generates heat, due to resistance in the coil units  40 . The heat from the coil units  40  is subsequently transferred to the reaction assembly  20 . This can cause expansion and distortion of the reaction assembly  20 . Further, the heat from the coil units  40  can be transferred to the surrounding environment, including the air surrounding the coil units  40 . This can adversely influence a measurement system (not shown in  FIG. 1 ) that measures the position of the stage  14  and the device  16 . For example, certain measurement systems utilize one or more interferometers. The heat from the conductor array  36  changes the index of refraction of the surrounding air. This reduces the accuracy of the measurement system and degrades machine positioning accuracy. Moreover, the resistance of the coil units  40  increases as temperature increases. This exacerbates the heating problem and reduces the performance and life of the stage mover  16 . 
     In certain embodiments, to reduce the influence of the heat from the coil units  40 , the present invention actively cools the reaction assembly  20  and the coil units  40  using the fluid distribution network  28 . 
     The reaction assembly  20  counteracts, reduces and/or minimizes the influence of the reaction forces from the stage mover  18  on the position of the stage base  12  relative to the mounting base  1324 . This minimizes the distortion of the stage base  12  and improves the positioning performance of the stage assembly  10 . Further, for an exposure apparatus  1334 , this allows for more accurate positioning of the semiconductor wafer. 
     As provided above, in the embodiment illustrated in  FIG. 1 , the conductor array  36  of the stage mover  18  is coupled to the reaction assembly  20 . With this design, the reaction forces generated by the stage mover  18  are transferred to the reaction assembly  20 . As a result thereof, when the stage mover  18  applies a force to move the stage  14 , an equal and opposite reaction force is applied to the reaction assembly  20 . 
     In  FIG. 1 , the reaction assembly  20  includes the generally rectangular shaped countermass assembly  26 , which can be maintained above the stage base  12  with a reaction bearing (not shown), e.g. a vacuum preload type fluid bearing. For example, the bottom of the countermass  26  of the reaction assembly  20  can include a plurality of spaced apart fluid outlets (not shown), and a plurality of spaced apart fluid inlets (not shown). Pressurized fluid (not shown) can be released from the fluid outlets towards the stage base  12  and a vacuum can be pulled in the fluid inlets to create a vacuum preload type, fluid bearing between the stage base  12  and the countermass  26 . In this embodiment, the reaction bearing allows for motion of the reaction assembly  20  relative to the stage base  12  along the X axis, along the Y axis and about the Z axis. Alternatively, for example, the reaction bearing can be a magnetic type bearing that provides for relative motion along the X, Y, and Z axes and about the X, Y, and Z axes, or a roller bearing type assembly. 
     With this design, through the principle of conservation of momentum, (i) movement of the stage  14  with the stage mover  16  along the X axis in a first X direction along the X axis, generates an equal but opposite X reaction force that moves the reaction assembly  20  in a second X direction that is opposite the first X direction along the X axis; (ii) movement of the stage  14  with the stage mover  16  along the Y axis in a first Y direction, generates an equal but opposite Y reaction force that moves the reaction assembly  20  in a second Y direction that is opposite the first Y direction along the Y axis; and (iii) movement of the stage  14  with the stage mover  16  about the Z axis in a first theta Z direction, generates an equal but opposite theta Z reaction force (torque) that moves the reaction assembly  20  in a second theta Z direction that is opposite the first theta Z direction about the Z axis. 
     The design of the reaction assembly  20  can be varied to suit the design requirements of the stage assembly  10 . In certain embodiments, the ratio of the mass of the reaction assembly  20  to the mass of the stage  14  is relatively high. This will minimize the movement of the reaction assembly  20  and minimize the required travel of the reaction assembly  20 . A suitable ratio of the mass of the reaction assembly  20  to the mass of the stage  14  is between approximately 10:1 and 30:1. A larger mass ratio is better, but is limited by the physical size of the reaction assembly  20 . 
     In one embodiment, the reaction assembly  20  is made from a non-electrically conductive, non-magnetic material, such as low electrical conductivity stainless steel or titanium, or non-electrically conductive plastic or ceramic. 
     Additionally, one or more movers (not shown) can be used to adjust the position of the reaction assembly  20  relative to the stage base  12  and/or to counteract moments imparted onto the reaction assembly  20 . For example, the movers can include one or more rotary motors, voice coil motors, linear motors, electromagnetic actuators, or other type of actuators. 
     The fluid distribution network  28  reduces the influence of the heat from the coil units  40  of the conductor array  36  from adversely influencing the other components of the stage assembly  10  and the assemblies nearby the stage assembly  10 . In one embodiment, the fluid distribution network  28  efficiently reduces the amount of heat transferred from the coil units  40  to the surrounding environment. 
     The design of the fluid distribution network  28  can vary. In certain embodiments, the fluid distribution network  28  uses a multi-layer design approach, with each layer being designed to minimize or inhibit pressure drops and the impact of thermal deformation on the countermass  26 . As described herein, the fluid management provided via the fluid distribution network  28  and the structural support of the countermass  26  and the other supporting members of the stage assembly  10  are mostly decoupled from one another. 
     As described in greater detail herein below, in some embodiments, the fluid distribution network  28  can include and/or incorporate two distinct fluid networks. In particular, the fluid distribution network  28  can include the body fluid source  32  (sometimes referred to as the “first distribution network” or the “Coil Temperature Control (CTC) network”) that is used for cooling the coils within the coil units  40 , which removes the bulk of the heat from the conductor array  36 . Additionally, the fluid distribution network  28  can further include the surface fluid source  34  (sometimes referred to as the “second distribution network” or the “Surface Temperature Control (STC) network”) that is used for cooling and/or maintaining the temperature of the upper surface (typically the surface that faces the magnet array) of the individual coil units  40 . The second distribution network  34  is used to shield the area above the coil units  40  from heat generated by the coil units  40 . For mechanical considerations, because of the delicate nature of the coil units  40 , the internal fluid pressure is limited. In order to achieve the often desired high flow rates to the large conductor array  36 , limiting the pressure drop downstream to the coil units  40  is critical. 
     Further, the fluid distribution network  28  must be able to minimize and/or inhibit heat transfer to the countermass assembly  26 . With the present design, the circulation fluid  30  can be provided at a high rate while minimizing and/or inhibiting thermal deformation by having the circulation fluid  30  flow primarily in non-structural parts. More specifically, with the large mass of the stage  14  and its high acceleration during certain applications, a significant amount of heat needs to be removed from the coils units  40  and the countermass assembly  26 . Even with a high flow rate of the circulation fluid  30  there can be a substantial rise in fluid temperature. The difference between the hot and cold fluid, if not managed properly, can lead to thermal deformation of the countermass assembly  26 , which in turn could impact the fly height of the stage  14 , the accuracy of sensors, and the overall precision of the stage assembly  10 . Moreover, with the design illustrated and described herein, the fluid distribution network  28  can be used to inhibit the transfer of heat from the coil units  40  of the conductor array  36  to the surrounding environment. 
     The type of circulation fluid  30  that is utilized within the fluid distribution network  28  can be varied. For example, in certain embodiments, the circulation fluid  30  can be water or another appropriate cooling fluid. Additionally, the circulation fluid  30  can also be referred to as a coolant. 
     As provided herein, during use of the stage assembly  10 , the device  16  is moved by the stage mover  18 . Typically, during use of the stage assembly  10 , more current is directed to certain of the coil units  40  as compared to other coil units  40 . For example, certain coil units  40  are primarily used to move the device  16 , e.g., a wafer, during the scanning portion of an exposure. These coil units  40  will generate more heat and, thus, will require more cooling. As provided herein, the fluid distribution network  28  is uniquely designed to provide more cooling to certain coil units  40  and/or groups of coil units  40 . The design of the fluid distribution network  28  is discussed in more detail below. 
     The control system  22  is electrically connected to, and directs and controls electrical current to the coil units  40  of the stage mover  18  to precisely position the device  16 . Further, the control system  22  is electrically connected to and controls the fluid distribution network  28  to accurately control the temperature of the reaction assembly  20  and the conductor units  40 . The control system  22  can include one or more processors and/or circuits. 
     The design of the countermass assembly  26  can be varied pursuant to the teachings provided herein to suit the specific design requirements of the stage assembly  10 . In one embodiment, the countermass assembly  20  includes (i) a fluid distribution plate assembly  48 , (ii) a support frame  50 , (iii) a plate attachment assembly  51 ; and (iv) one or more countermasses  52 . 
     The fluid distribution plate assembly  48  supports the coil units  40  and also functions as a manifold to direct the circulation fluid  30  between the fluid distribution network  28  and the coil units  40 . Thus, in certain embodiments, the fluid distribution plate assembly  48  provides structural support for the coil units  40  and is used with the fluid distribution network  28  for thermal control of the coil units  40 . With this design, (i) reaction forces from the coil units  40  are transferred to the distribution plate assembly  48 , then the plate attachment assembly  51 , and subsequently to the support frame  50  and the countermass weights  52 ; and (iii) the circulation fluid  30  travels between the coil units  40  and the fluid distribution network  28  through the distribution plate assembly  48 . 
     In certain embodiments, the fluid distribution plate assembly  48  is designed to enable the fluid distribution network  28  to be effectively decoupled from the physical structure of the stage assembly  10  to more effectively manage the thermal strain that may otherwise exist within the countermass assembly  26 . In certain embodiments, the fluid distribution plate assembly  48  is the only part of the countermass assembly  26  that is used with the fluid distribution network  28  for thermal control of the coil units  40 . Stated in another fashion, the only part of the countermass assembly  26  in which the fluid  30  flows is the distribution plate assembly  48 . Thus, in these embodiments, (i) the fluid distribution plate assembly  48  is the only part of the countermass assembly  26  that is subjected to potential thermal deformation caused by the circulation fluid  30 ; and (iii) the other components (e.g. the support frame  50 , the plate attachment assembly  51 , and the countermasses  52 ) of the countermass assembly  26  are not subjected to potential thermal deformation caused by the circulation fluid  30 . This minimizes the potential for thermal stain of the countermass assembly  26  that can adversely influence the position of the stage  14 . 
     Moreover, in certain embodiments, the mass of the fluid distribution plate assembly  48  is relatively small when compared to the other components (e.g. the support frame  50 , the plate attachment assembly  51 , and the countermasses  52 ) of the countermass assembly  26 . In this embodiment, when the circulation fluid  30  only flows through the fluid distribution plate assembly  48  of the countermass assembly  26 , the fluid distribution network  28  is substantially decoupled from the physical structure of the countermass assembly  26  to more effectively manage the thermal strain that may otherwise exist within the countermass assembly  26 . In alternative, non-exclusive embodiments, the circulation fluid  30  only flows through five, ten, fifteen, or twenty percent of the mass of the countermass assembly  26 . 
     In the embodiment illustrated in  FIG. 1 , the fluid distribution plate assembly  48  is generally rectangular plate shaped and rigid. In certain embodiments, the fluid distribution plate assembly  48  can be made as a modular unit that includes a plurality of substantially similar fluid distribution plates  48 A. As a non-exclusive example, the fluid distribution plate assembly  48  can include eleven fluid distribution plates  48 A that are secured together in a side-by-side manner so as to provide a supporting mechanism to support the plurality of coil units  40 . In this embodiment, each fluid distribution plates  48 A is generally rectangular plate shaped and supports twenty-four separate coil units  40  (two rows of twelve coil units  40 ). Additionally, in this embodiment, each distribution plate  48 A extends from one side of the distribution plate assembly  48  to the other side of the distribution plate assembly  48  in the X-direction (i.e. the shorter dimension as illustrated in the Figures), and the distribution plates  248  are positioned side-by-side in the Y-direction (i.e. the longer dimension as illustrated in the Figures). 
     Alternatively, the fluid distribution plate  48 A can have a different shape or design. Still alternatively, the distribution plate assembly  48  can be made as single plate. 
     The support frame  50  supports the other components of the countermass assembly  26 . In  FIG. 1 , the support frame  50  is generally rectangular plate shaped and rigid. Further, the support frame  50  is positioned adjacent to the stage base  12 . In certain embodiments, the circulation fluid  30  does not flow through (or contact) the support frame  50 . 
     The plate attachment assembly  51  is rigid and supports and rigidly couples the fluid distribution plate assembly  48  to the support frame  50 , while allowing space for the fluid distribution network  28  to access a bottom of the fluid distribution plate assembly  48 . In certain embodiments, the circulation fluid  30  does not flow through (or contact) the plate attachment assembly  51 . 
     The one or more countermass weights  52  are coupled to the distribution plate assembly  48  and/or the support frame  50  to provide a greater mass to the reaction assembly  20  so as to minimize or otherwise limit any movement of the reaction assembly  20  in reaction to the movement of the stage  14  (illustrated in  FIG. 1 ) by the stage mover  18 . For example, in one embodiment, the countermass weights  52  can comprise tungsten blocks that are coupled to an end of the distribution plate assembly  48  and/or the support frame  50 . Alternatively, the countermass weights  52  can be made from another suitable material, and/or can be positioned in a different manner relative to the distribution plate assembly  48  and/or the support frame  50 . In certain embodiments, the circulation fluid  30  does not flow through (or contact) the one or more countermass weights  52 . 
     Additionally, as noted above, in certain embodiments, the countermass weights  52  can have sufficient mass such that the overall mass of the reaction assembly  20  versus the mass of the stage  14  can be between approximately 10:1 and 30:1. Alternatively, the mass of the reaction assembly  20  versus the mass of the stage  14  can be greater than 30:1 or less than 10:1. 
       FIG. 2A  is a simplified, non-exclusive side view of one coil unit  40 , a portion of the distribution plate assembly  48 , and a portion of the fluid distribution network  28 . The design of each of these components can be varied pursuant to the teachings provided herein. 
     In  FIG. 2A , the coil unit  40  is generally rectangular shaped. In this non-exclusive embodiment, moving from the bottom to the top, the coil unit  40  includes (i) a lower body circulation plate  240 A that is substantially rectangular plate shaped and includes one or more fluid passageways  240 B, e.g. microchannels, (illustrated in phantom); (ii) a coil set  240 C that includes one or more X coils and/or one or more Y coils; (iii) an upper body circulation plate  240 D that is substantially rectangular plate shaped and includes one or more fluid passageways  240 E (illustrated in phantom); and (iv) an upper surface circulation plate  240 F that is substantially rectangular plate shaped and includes one or more fluid passageways  240 G (illustrated in phantom). With this design, (i) the body fluid source  32  (illustrated in  FIG. 1 ) directs the fluid  30  (illustrated in  FIG. 1 ) through the body circulation plates  240 A,  240 D to remove the bulk of heat generated by the coil set  240 C, and (ii) the surface fluid source  34  (illustrated in  FIG. 1 ) directs the fluid  30  (illustrated in  FIG. 1 ) through the surface circulation plate  240 F to provide a thermal shield for the coil unit  40  and to maintain the surface temperature of each conductor unit  40  at the desired temperature to inhibit the transfer of heat from each conductor unit  40 . 
     The design of the coil set  240 C and the number of conductors in each coil set  240 C can be varied to suit the design requirements of the stage mover  16  (illustrated in  FIG. 1 ). For a three phase planar motor, each coil set  240 C includes three adjacent racetrack shaped coils that are aligned side by side. 
     In  FIG. 2A , the coil unit  40  is mounted on a top surface  248 A of the distribution plate assembly  48 . As illustrated in  FIG. 2A , one or more sealers  254  (e.g., O-rings) can be positioned between the coil unit  40  and the distribution plate assembly  48  to connect one or more distribution fluid passageways  248 B (illustrated in phantom) in the distribution plate assembly  248  to the coil unit  40 . With this design, the coil unit  40  can be urged against the distribution plate assembly  48  to seal the distribution fluid passageways  248 B in the distribution plate assembly  48  to the desired fluid passageways (not shown) in the coil unit  40 . 
     The distribution plate assembly  48  is generally rectangular shaped and includes the top surface  248 A, an opposed bottom surface  248 C and a plurality of distribution fluid passageways  248 B that connect the fluid distribution network  28  to the coil units  40 . Additionally, the distribution plate assembly  48  can include a separate unit aperture  248 D (illustrated in phantom) for each coil unit  40 . For example, the unit aperture  248 D can be a generally rectangular shaped opening that extends between the top surface  248 A and the bottom surface  248 C that facilitates the attachment of the coil units  40  and electrical connections to the coil units  40 . In certain embodiments, a portion of the coil unit  40  extends through the corresponding unit aperture  248 D. 
     Only a very small portion of the fluid distribution network  28  is illustrated in  FIG. 2A . Importantly, the fluid distribution network  28  is positioned directly adjacent to the bottom surface  248 C of the distribution plate assembly  48 . Further, the fluid distribution network  28  is directly attached to the distribution fluid passageways  248 B in the distribution plate assembly  48 . With this design, the circulation fluid  30  (illustrated in  FIG. 1 ) flows only through the fluid distribution network  28  and a small portion of the distribution plate assembly  48 , and not the rest of the countermass assembly  26  (illustrated in  FIG. 1 ). 
       FIG. 2B  is a perspective view of the coil unit  40  including the lower body circulation plate  240 A, the coil set  240 C, the upper body circulation plate  240 D, and the upper surface circulation plate  240 F. Additionally,  FIG. 2B  illustrates that the coil unit  40  includes (i) a body plate inlet  240 H that transfers the supply circulation fluid  30  (illustrated in  FIG. 1 ) received from the body fluid source  32  (illustrated in  FIG. 1 ) via the fluid distribution network  28  (illustrated in  FIG. 2A ) and the distribution plate assembly  48  (illustrated in  FIG. 2A ) to the body circulation plates  240 A,  240 D; (ii) a body plate outlet  2401  that transfers the return circulation fluid  30  received from the body circulation plates  240 A,  240 D to the body fluid source  32  via the distribution plate assembly  48  and the fluid distribution network  28 ; (iii) a surface plate inlet  240 J that transfers the supply circulation fluid  30  received from the surface fluid source  34  via the fluid distribution network  28  and the distribution plate assembly  48  to the surface circulation plate  240 F; and (iv) a surface plate outlet  240 K that transfers the return circulation fluid  30  received from the surface circulation plate  240 F to the surface fluid source  34  via the distribution plate assembly  48  and the fluid distribution network  28 . 
       FIG. 3A  is a top plan view of the distribution plate assembly  48  of  FIG. 2A . In this embodiment, the distribution plate assembly  48  defines a plurality of coil sites  348 A that are each designed to receive, retain, and direct fluid  30  (illustrated in  FIG. 1 ) to one of the coil units  40  (illustrated in  FIG. 1 ). In this embodiment, the distribution plate assembly  48  defines two hundred and sixty-four coil sites  348 A. Alternatively, the distribution plate assembly  48  can be designed to have more than or fewer than two hundred and sixty-four coil sites  348 A. 
     As illustrated in  FIG. 3A , for each coil site  348 A, the distribution plate assembly  48  includes four distribution fluid passageways  248 B and a separate unit aperture  248 D. In this embodiment, the fluid distribution plate assembly  48  is a modular unit that includes eleven fluid distribution plates  48 A that are secured together in a side-by-side manner so as to provide a supporting mechanism to support the plurality of coil units  40 . 
     As noted above, in certain applications, different areas of the stage mover  18  (illustrated in  FIG. 1 ) are used more often than others, thus generating more heat during the movement of the stage  14  (illustrated in  FIG. 1 ). Accordingly, differing amounts of heat can be generated near each of the distribution plate  48 A, and, thus, each of the distribution plate  48 A can require a differing amount of cooling (which can be controlled in any suitable manner, some of which are noted herein below). For example, in certain applications, the distribution plates  48 A can be designated as low use, medium use, or high use, depending on the required usage of the adjacent coil units  40  during movement of the stage  14 . 
       FIG. 3B  is a top plan view of one of the distribution plates  48 A of  FIG. 3A . In this embodiment, each fluid distribution plates  48 A is generally rectangular plate shaped and defines twenty-four separate each coil site  348 A arranged in two rows of twelve. As provided above, for each coil unit  40 , the four distribution fluid passageways  248 B can be referred to as (i) a body inlet passageway  348 B that is in fluid communication with the body plate inlet  240 H (illustrated in  FIG. 2B ) of the coil unit  40 ; (ii) a body outlet passageway  348 C that is in fluid communication with the body plate outlet  2401  (illustrated in FIG.  2 B) of the coil unit  40 ; (iii) a surface inlet passageway  348 D that is in fluid communication with the surface plate inlet  240 J (illustrated in  FIG. 2B ) of the coil unit  40 ; and (iv) a surface outlet passageway  348 E that is in fluid communication with the surface plate outlet  240 K (illustrated in  FIG. 2B ) of the coil unit  40 . 
     In this embodiment, (i) the body inlet passageway  348 B and the surface inlet passageway  348 D extend completely through the distribution plate  48 A, and (ii) the body outlet passageway  348 C and the surface outlet passageway  348 E extend only partly through the distribution plate  48 A. 
       FIG. 3B  also illustrates that each distribution plate  48 A includes (i) a body longitudinal passageway  348 F (illustrated in phantom) that is in fluid communication with the body outlet passageways  348 C; and a spaced apart surface longitudinal passageway  348 G (illustrated in phantom) that is in fluid communication with the surface outlet passageways  348 E. Further, the longitudinal passageways  348 F,  348 G extend along the distribution plate  48 A. With this design, (i) the fluid  30  (illustrated in  FIG. 1 ) that enters the body outlet passageways  348 C is transferred to the body longitudinal passageway  348 F, and (ii) the fluid  30  that enters the surface outlet passageways  348 E is transferred to the surface longitudinal passageway  348 G. 
     Thus, in certain embodiments, (i) the fluid  30  that has been circulated in each body circulation plate  240 A,  240 D (illustrated in  FIG. 2A ) is returned to the common body longitudinal passageway  348 F; and (ii) the fluid  30  that has been circulated in each surface circulation plate  240 F (illustrated in  FIG. 2A ) is returned to the common surface longitudinal passageway  348 G. This simplifies the pluming for the returning fluid  30 . With this design, for each distribution plate  48 A, (i) the common body longitudinal passageway  348 F functions as a manifold that receives and collects the circulation fluid  30  exiting the body circulation plates  240 A,  240 D of each coil unit  40 ; and (ii) the common surface longitudinal passageway  348 G functions as a manifold that receives and collects the circulation fluid  30  exiting the surface circulation plate  240 F of each coil unit  40 . 
     In certain embodiments, one or more of the passageways  348 B,  348 C,  348 D,  348 E can include one or more flow regulators (not illustrated) that regulate the volume and rate of fluid flow to the individual coil units  40 . Additionally and/or alternatively, such flow regulators can be included within the structure of the coil units  40  themselves. In one non-exclusive embodiment, one or more of the passageways  348 B,  348 C,  348 D,  348 E can be sized and shaped to function as a flow regulator that is sized to provide the desired flow rate based on the planned movement of the mover  18 . With this design, the coil units  40  that are used more will be affiliated with flow regulators having larger diameter channels (orifices), and coil units  40  that are used less will be affiliated with flow regulators having smaller diameter channels (orifices). Thus, one or more of the passageways  348 B,  348 C,  348 D,  348 E can be sized to suit the flow (cooling) requirements of the respective coil units  40  with the projected usage of the mover  18 . Moreover, in one embodiment, the passageways  348 B,  348 C,  348 D,  348 E can be sized during the design phase of the mover  18  based on the projected usage of the mover  18  to provide the appropriate flow rate to respective coil units  40 . 
     As a non-exclusive example, four different sizes can be used for the passageways  348 B,  348 C,  348 D,  348 E. In this design, (i) the first (largest) diameter can be used for coil units  40  that are used the most; (ii) the second (next largest) diameter can be used for coil units  40  that are used the second most; (iii) the third (largest) diameter can be used for coil units  40  that are used the third most; and (iv) the fourth (largest) diameter can be used for coil units  40  that are used the least. It should be noted that more than four or fewer than four channel diameters can be used. 
     Alternatively, one or more of the flow regulators can be an adjustable valve that is controlled to adjust and/or regulate the volume and rate of fluid flow depending on the specific cooling requirements for each of the individual coil units  40 . In various applications, the control system  22  (illustrated in  FIG. 1 ) can be utilized to provide the necessary and desired regulation of the valves to provide the desired and selective cooling of the individual coil units  40 . 
     As noted above, by providing the relatively short plate passageways  348 B,  348 C,  348 D,  348 E,  348 F,  348 G which are the only fluid paths through the physical structure of the stage assembly  10  (illustrated in  FIG. 1 ), the fluid distribution network  28  (illustrated in  FIG. 1 ) can be more effectively decoupled from the physical structure of the stage assembly  10 , so as to more effectively manage the thermal strain that may otherwise exist within the stage assembly  10 , e.g., within the stage mover  18  (illustrated in  FIG. 1 ). 
       FIG. 3C  is a bottom plan view of the portion of the distribution plate assembly  48 A of  FIG. 3B , including the body inlet passageway  348 B, the surface inlet passageway  348 D, the body longitudinal passageway  348 F (illustrated in phantom), and the surface longitudinal passageway  348 G (illustrated in phantom). 
       FIG. 3C  also illustrates that, in this non-exclusive embodiment, (i) the body longitudinal passageway  348 F includes four outlet passageways  349 A that are used to connect the body longitudinal passageway  348 F to the body fluid source  32  (illustrated in  FIG. 1 ); and (ii) the surface longitudinal passageway  348 G includes two outlet passageways  349 B that are used to connect the surface longitudinal passageway  348 G to the surface fluid source  34  (illustrated in  FIG. 1 ). 
       FIG. 3D  is a cut-away view of the distribution plate  48 A taken on line  3 D- 3 D in  FIG. 3C  that illustrates the first transverse passageway  348 E, the second transverse passageway  348 F, one outlet passageways  349 A, and one outlet passageway  349 B (illustrated in phantom). 
     In certain embodiments, the distribution plate  48 A can be formed from multiple plate members that can be fusion bonded together. In one embodiment, each of the plate members can be formed from a stainless steel material. Alternatively, one or more of the plate members can be formed from another suitable material. 
       FIG. 4A  is a bottom view of the distribution plate  48 A, and a portion of the fluid distribution network  28  positioned adjacent to the bottom surface  248 C of the distribution plate  48 . As provided herein, the majority of the fluid distribution network  28  is positioned below, near and/or substantially adjacent to the bottom surface  248 C of the distribution plate assembly  48 . With this design, the circulation fluid  30  (illustrated in  FIG. 1 ) does not flow through the bulk of the countermass assembly  26 . 
     In this embodiment, for each distribution plate  48 A, the fluid distribution network  28  includes a separate, adjacent conduit assembly  460  that is positioned directly adjacent to the bottom surface  248 C of the distribution plate  48 A. In one embodiment, the adjacent conduit assembly  460  provides a path below the distribution plate  48 A and near and/or substantially adjacent to the bottom surface  248 C for directing the circulation fluid  30  (illustrated in  FIG. 1 ) into the distribution plate  48 A. For example, the adjacent conduit assembly  460  can include (i) a body supply conduit  462  that is in fluid communication with the body inlet passageway  348 B (illustrated in  FIG. 3C ) of each coil site  348 A of the distribution plate  48 A; and (ii) a surface supply conduit  464  that is in fluid communication with the surface inlet passageway  348 D (illustrated in  FIG. 3C ) of each coil site  348 A of the distribution plate  48 A. 
     With this design, the adjacent conduit assembly  460  is designed to broadly distribute the circulation fluid  30  for the coil sites  348 A substantially adjacent to the distribution plate  48 A prior to the circulation fluid  30  being directed through the distribution plate  48 A in order to provide the desired cooling of the coil units  40  (illustrated in  FIG. 1 ). By effectively distributing the circulation fluid  30  below the distribution plate  48 A (i.e. not within the distribution plate assembly  48 A), the fluid distribution network  28  can be more effectively decoupled from the physical structure of the countermass assembly  26  (illustrated in  FIG. 1 ), so as to more effectively manage the thermal strain that may otherwise exist. 
     As provided herein, the adjacent conduit assembly  460  functions as a manifold for the cool inlet circulation fluid  30  into the distribution plate  48 A. More specifically, in this embodiment, (i) the body supply conduit  462  is used as a manifold to distribute the inlet circulation fluid  30  of each coil site  348 A; and (ii) the surface supply conduit  464  is used as a manifold to distribute the inlet circulation fluid  30  of each coil site  348 A. It should be noted that (i) the circulation fluid  30  distributed by the body supply conduit  462  is directed to the body circulation plates  240 A,  240 D (illustrated in  FIG. 2A ) of each coil unit  40 ; and (ii) the circulation fluid  30  distributed by the surface supply conduit  462  is directed to the surface circulation plate  240 F (illustrated in  FIG. 2A ) of each coil unit  40 . 
     It should be noted that the adjacent conduit assembly  460  does not route the heated circulation fluid  30  that has exited each coil unit  40 . Thus, because only the adjacent conduit assembly  460  of the fluid distribution network  28  is illustrated in  FIG. 4A , (i) the four outlet passageways  349 A that are in fluid communication with the body longitudinal passageway  348 F (illustrated in  FIG. 3C ) are still open; and (ii) the two outlet passageways  349 B that are in fluid communication with the surface longitudinal passageway  348 G (illustrated in  FIG. 3C ) are still open. Thus, in this embodiment, the adjacent conduit assembly  460  does not route the returning fluid  30  from the coil units  40 . 
     With this design, the adjacent conduit assembly  460  provides a stand alone means for distribution of the circulation fluid  30  (illustrated in  FIG. 1 ) below, near and/or substantially adjacent to the bottom surface  248 C of the individual distribution plate  48 A. Stated in another fashion, an individual and separate adjacent conduit assembly  460  is utilized to effectively distribute the circulation fluid  30  substantially adjacent to the bottom surface  248 C of each distribution plate  48 A prior to the circulation fluid  30  being directed through the distribution plate  48 A. 
       FIG. 4B  is a bottom view of the adjacent conduit assembly  460  including the body supply conduit  462  and the surface supply conduit  464  from  FIG. 4A . In this embodiment, the body supply conduit  462  includes a main body conduit  462 A and a plurality of substantially parallel and spaced apart, branch body conduits  462 B that cantilever away from and that are in fluid communication with the main body conduit  462 A. In this embodiment, each branch body conduit  462 B (or the main body conduit  462 A near the branch) provides circulation fluid  30  to two coil sites  348 A. Thus, the number of branch body conduits  462 B is equal to the number of pairs of coil sites  348 A for the distribution plate  48 A. In  FIG. 4B , the body supply conduit  462  includes twelve branch body conduits  462 B. Moreover, in this embodiment, the main body conduit  462 A includes three spaced apart body conduit inlets  462 C to receive the supply circulation fluid  30  (illustrated in  FIG. 1 ) from the body fluid source  32  (illustrated in  FIG. 1 ). 
     Somewhat similarly, in this embodiment, the surface supply conduit  464  includes a main surface conduit  464 A and a plurality of substantially parallel and spaced apart, branch surface conduits  464 B that cantilever away from and that are in fluid communication with the main surface conduit  464 A. In this embodiment, each branch surface conduit  464 B (or the main surface conduit  464 A near the branch) provides circulation fluid  30  to two coil sites  348 A. Thus, the number of branch surface conduits  464 B is equal to the number of pairs of coil sites  348 A for the distribution plate  48 A. In  FIG. 4B , the surface supply conduit  464  includes twelve branch surface conduits  464 B. Moreover, in this embodiment, the surface body conduit  464 A includes two spaced apart surface conduit inlets  464 C to receive the supply circulation fluid  30  (illustrated in  FIG. 1 ) from the body fluid source  34  (illustrated in  FIG. 1 ). 
     It should be noted that in this embodiment, with reference to  FIGS. 4A and 4B , each of the distribution plates  48 A includes eleven, separate fluid connection openings, namely four separate body outlet passageways  349 A, two separate surface outlet passageways  349 B, three body conduit inlets  462 C, and two surface conduit inlets  464 C (4+2+3+2=11). As a result thereof, the rest of the fluid distribution network  28  must provide fluid connections for the eleven, separate fluid connection openings for each distribution plate  48 A. 
       FIG. 4C  is a top view of the adjacent conduit assembly  460  of  FIG. 4B . Additionally,  FIG. 4D  is an enlarged cut-away perspective view of a portion of the adjacent conduit assembly  460  from  FIG. 4C . As shown in this embodiment, (i) the body supply conduit  462  include a separate body conduit outlet  462 D for each coil site  348 A serviced (e.g. twenty four in this example); and (ii) the surface supply conduit  464  include a separate surface conduit outlet  464 D for each coil site  348 A serviced (e.g. twenty four in this example). For each coil site  348 A, (i) the body conduit outlet  462 D is in fluid communication with the corresponding body inlet passageway  348 B (illustrated in  FIG. 3C ) of the distribution plate  48 A; and (ii) the surface conduit outlet  464 D is in fluid communication with the corresponding surface inlet passageway  348 D (illustrated in  FIG. 3C ) of the distribution plate  48 A. 
     It should be noted that (i) half of the branch body conduits  462 B include two body conduit outlets  462 D, and (ii) half of the branch body conduits  462 B include only one body conduit outlet  462 D, with the other body conduit outlets  462 D being positioned in the main body conduit  462 A near the respective branch body conduit  462 B. Similarly, (i) half of the branch surface conduits  464 B include two surface conduit outlets  464 D, and (ii) half of the branch surface conduits  464 B include only one surface conduit outlet  464 D, with the other surface conduit outlets  464 D being positioned in the surface body conduit  464 A near the respective branch surface conduit  464 B. 
     It should be understood that in certain embodiments, that the body supply conduit  462  and/or the surface supply conduit  464  can include one or more flow regulators (not illustrated) that individually (or as a group) regulate the volume and rate of the circulation fluid  30  to one or more of the coil sites  348 A. 
     As provided above, the design of the fluid distribution network  28  can be varied to suit the specific requirements of the stage assembly  10  (illustrated in  FIG. 1 ) with which the fluid distribution network  28  is utilized.  FIG. 5A  is a perspective view of another portion of the fluid distribution network  28 . In one embodiment, the portion of the fluid distribution network  28  illustrated in  FIG. 5A  is used to connect in fluid communication the (i) the body fluid source  32  (illustrated in  FIG. 1 ) to the body supply conduit  462  (illustrated in  FIG. 4A ) for each distribution plate  48 A to supply the body circulation fluid  30  (illustrated in  FIG. 1 ) to each coil unit  40  (illustrated in  FIG. 1 ); (ii) the outlet passageways  349 A (illustrated in  FIG. 3C ) for each distribution plate  48 A to the body fluid source  32  to return the body circulation fluid  30  from each coil unit  40 ; (iii) the surface fluid source  34  (illustrated in  FIG. 1 ) to the surface supply conduit  464  (illustrated in  FIG. 4A ) for each distribution plate  48 A to supply the surface circulation fluid  30  (illustrated in  FIG. 1 ) to each coil unit  40  (illustrated in  FIG. 1 ); and (iv) the outlet passageways  349 B (illustrated in  FIG. 3C ) for each distribution plate  48 A to the surface fluid source  34  to return the surface circulation fluid  30  from each coil unit  40 . 
     In one embodiment, the portion of the fluid distribution network  28  illustrated in  FIG. 5A  is positioned below and adjacent to the body supply conduit  462  and the surface supply conduit  464  for each distribution plate  48 A. With this design, the fluid distribution network  28  is substantially thermally decoupled from the rest of the countermass assembly  26 . 
     In the non-exclusive embodiment illustrated in  FIG. 5A , the fluid distribution network  28  includes (i) a first distribution hub  570  (also sometimes referred to as a “first gorgon”), (ii) a second distribution hub  572  (also sometimes referred to as a “second gorgon”) that is a spaced apart from and that is a mirror image of the first distribution hub  570 ; and (iii) a distribution conduit array  574  (also sometimes referred to as “qanats”) that is in fluid communication with the distribution hubs  570 ,  572 . In this embodiment, (i) the distribution hubs  570 ,  572  are connected to and are in fluid communication with the fluid sources  34 ,  36 ; and (ii) the distribution conduit array  574  is in fluid communication with the eleven, separate fluid connection openings, namely four separate body outlet passageways  349 A, two separate surface outlet passageways  349 B, three body conduit inlets  462 C, and two surface conduit inlets  464 C (see  FIGS. 4A and 4B ) for each distribution plate  48 A. As provided above, in the embodiment illustrated in  FIG. 3A , the distribution plate assembly  48  includes eleven separate distribution plates  48 A. Further, each distribution plate  48 A includes eleven separate fluid connection openings. Thus, in this embodiment, the distribution conduit array  574  is designed provide a separate fluid connection  576  to the one hundred and twenty-one different fluid connection openings of the distribution plate assembly  48 . In  FIG. 5A , the distribution conduit array  574  includes eleven separate, substantially equally spaced apart and substantially parallel, distribution conduits  578  and each distribution conduit  578  includes eleven separate fluid connections  576  to provide fluid connections to the one hundred and twenty-one different fluid connection openings of the distribution plate assembly  48 . 
     Each of the eleven separate fluid connections  576  of each of the distribution conduits  578  is connected in fluid communication to a different one of the distribution plates  48 A. Stated in another fashion, for each distribution plate  48 A, each distribution conduits  578  provides a single separate fluid connection  576 . Thus, in this design, the distribution conduits  578  are positioned transverse to the long axis of each distribution plate  48 A. As a result thereof, each of the distribution conduits  578  extends over each of the distribution plates  48 A. 
     It should be noted that with the present design, the fluid distribution network  28  can easily be scaled to fit a distribution plate assembly  48  that is sized differently than provided herein. 
       FIG. 5B  is a top view of the first distribution hub  570 , the second distribution hub  572  and the distribution conduit array  574 . Additionally, one of the eleven side-by-side distribution plates  48 A and its corresponding adjacent conduit assembly  460  is illustrated in phantom for reference. As provided above, each distribution conduit  578  is in fluid communication once via the eleven separate fluid connections  576  to each distribution plate  48 A. 
     In this embodiment, as provided above, the distribution conduit array  574  includes eleven distribution conduits  578  that are substantially parallel to one another, and each of the distribution conduits  578  extends along (or parallel to) a first axis, e.g., the Y axis (transverse to the distribution plates  48 A); and the distribution conduits  578  are spaced apart from one another along (or parallel to) a second axis, e.g., the X axis. Alternatively, the fluid distribution network  28  can be designed to include greater than eleven or less than eleven distribution conduits  578 , and/or the distribution conduits  578  can have a different positioning and/or orientation relative to one another. 
     As provided herein, the fluid distribution network  28  is in fluid communication with the fluid sources  34 ,  36  to provide the necessary and desired fluid path for (i) the inlet body circulation fluid  30  (illustrated in  FIG. 1 ) from the body fluid source  32  that is to be delivered to body circulation plates  240 A,  240 D of each coil unit  40 ; (ii) the returning body circulation fluid  30  from the body circulation plates  240 A,  240 D of each coil unit  40  to the body fluid source  32 ; (iii) the inlet surface circulation fluid  30  from the surface fluid source  34  that is to be delivered to surface circulation plate  240 F of each coil unit  40 ; and (iv) the returning surface circulation fluid  30  from the surface circulation plate  240 F of each coil unit  40  to the surface fluid source  34 . 
     In  FIG. 5B , the first distribution hub  570  and the second distribution hub  572  cooperate to be in fluid communication twice with each distribution conduit  578 . Further, in the non-exclusive embodiment illustrated in  FIG. 5B , the fluid distribution network  28  is designed and plumed so that (i) three of the distribution conduits  578  (labeled  578 B 1 ) carry inlet body circulation fluid  30  from the body fluid source  32 ; (ii) four of the distribution conduits  578  (labeled  578 BR) carry returning body circulation fluid  30  from the distribution plates  48 A; (iii) two of the distribution conduits  578  (labeled  578 S 1 ) carry inlet surface circulation fluid  30  from the surface fluid source  34 ; and (iv) two of the distribution conduits  578  (labeled  578 SR) carry returning surface circulation fluid  30  from the distribution plates  48 A. With this embodiment, the eleven distribution conduits  578  can each be coupled once for each of the distribution plates  48 A at the eleven, separate fluid connection openings, namely four separate body outlet passageways  349 A, two separate surface outlet passageways  349 B, three body conduit inlets  462 C, and two surface conduit inlets  464 C (see  FIGS. 4A and 4B ). 
     The arrangement of the distribution conduits  578  can vary. In the non-exclusive embodiment illustrated in  FIG. 5B , moving from the top to bottom, the distribution conduits  578  are arranged as follows: (i) the first distribution conduit  578  is labeled  578 BR because it is carrying returning body circulation fluid  30 ; (ii) the second distribution conduit  578  is labeled  578 SS because it is carrying inlet (supply) surface circulation fluid  30 ; (iii) the third distribution conduit  578  is labeled  578 SR because it is carrying returning surface circulation fluid  30 ; (iv) the fourth distribution conduits  578  is labeled  578 BS because it is carrying inlet (supply) body circulation fluid  30 ; (v) the fifth distribution conduit  578  is labeled  578 BR because it is carrying returning body circulation fluid  30 ; (vi) the sixth distribution conduit  578  is labeled  578 BS because it is carrying inlet (supply) body circulation fluid  30 ; (vii) the seventh distribution conduit  578  is labeled  578 BR because it is carrying returning body circulation fluid  30 ; (viii) the eighth distribution conduit  578  is labeled  578 BS because it is carrying inlet (supply) body circulation fluid  30 ; (ix) the ninth distribution conduit  578  is labeled  578 SR because it is carrying returning surface circulation fluid  30 ; (x) tenth distribution conduit  578  is labeled  578 SS because it is carrying inlet (supply) surface circulation fluid  30 ; and (xi) the eleventh distribution conduit  578  is labeled  578 BR because it is carrying returning body circulation fluid  30 ; 
     Further, the first distribution hub  570  is connected (i) twice to the first distribution conduit  578 , the second distribution conduit  578 , the third distribution conduit  578 , the fourth distribution conduits  578 , and the fifth distribution conduit  578 ; and (i) once to the sixth distribution conduit  578 . 
     Somewhat similarly, the second distribution hub  572  is connected (i) once to the sixth distribution conduit  578  and (i) twice to the seventh distribution conduit  578 , the eighth distribution conduit  578 , the ninth distribution conduit  578 , the tenth distribution conduits  578 , and the eleventh distribution conduit  578 . 
     It should be noted that fluid distribution network  28  can include one or more valves or regulars (not shown) that can be used to regulate flow. 
       FIG. 6A  is a bottom perspective view,  FIG. 6B  is a top view, and is an inverted side view of the distribution conduit array  574 . As provided above each distribution conduit  578  includes eleven, spaced apart, separate fluid connections  576 , with one fluid connector from each distribution conduit  578  being connected each distribution plate  48 A or corresponding adjacent conduit assembly  460 . Additionally, in this embodiment, each distribution conduit  578  includes one or more hub connectors  680  for fluid connection to the respective distribution hub  570 ,  572 . In the specific illustrated embodiment, each distribution conduit  578  includes two space apart hub connectors  680 , which can function as either an inlet to or an outlet from the respective distribution conduit  578  depending on whether the individual distribution conduit  578  is part of the fluid supply trip or the fluid return trip. 
       FIG. 6C  illustrates the size and positioning of the hub connectors  680  and the fluid connections  576  along the length of one of the distribution conduits  578 . 
       FIG. 7A  is a bottom perspective view, and  FIG. 7B  is a bottom view of the distribution hubs  570 ,  572  of the fluid distribution network  28 . In this embodiment, the first distribution hub  570  includes (i) a first manifold  782  having a plurality of manifold openings  784  that are connected to and that are in fluid communication with the fluid sources  34 ,  36 , and (ii) eleven, first manifold conduits  786  that are in fluid communication with the first manifold  782 . Similarly, the second distribution hub  572  includes (i) a second manifold  788  having a plurality of manifold openings  790  that are connected to and that are in fluid communication with the fluid sources  34 ,  36 , and (ii) eleven, second manifold conduits  792  that are in fluid communication with the second manifold  786 . 
     The number of manifold openings  784 ,  790 , and manifold conduits  786 ,  792  can be varied to suit the requirements of the system. In one embodiment, the first distribution hub  570  include eleven manifold openings  784 , and eleven manifold conduits  786 ; and the second distribution hub  572  include eleven manifold openings  790 , and eleven manifold conduits  792 . 
     The fluid distribution network  28  is designed and plumed so that (i) three of the first manifold openings  784  and three of the first manifold conduits  786  carry inlet body circulation fluid  30  from the body fluid source  32 ; (ii) four of the first manifold openings  784  and four of the first manifold conduits  786  carry returning body circulation fluid  30  from the distribution plates  48 A; (iii) two of the first manifold openings  784  and two of the first manifold conduits  786  carry inlet surface circulation fluid  30  from the surface fluid source  34 ; (iv) two of the first manifold openings  784  and two of the first manifold conduits  786  carry returning surface circulation fluid  30  from the distribution plates  48 A; (v) three of the second manifold openings  790  and three of the second manifold conduits  792  carry inlet body circulation fluid  30  from the body fluid source  32 ; (vi) four of the second manifold openings  790  and four of the second manifold conduits  792  carry returning body circulation fluid  30  from the distribution plates  48 A; (vii) two of the second manifold openings  790  and two of the second manifold conduits  792  carry inlet surface circulation fluid  30  from the surface fluid source  34 ; and (viii) two of the second manifold openings  790  and two of the second manifold conduits  792  carry returning surface circulation fluid  30  from the distribution plates  48 A 
       FIG. 8A  is a perspective view of a connector  894  that can be used to connect a portion of the fluid distribution network  28  (illustrated in  FIG. 1 ) to the distribution plate  48 A (illustrated in  FIG. 1 ). Additionally,  FIG. 8B  is a perspective view of a portion of the distribution plate  48 A and the connector  894 . In one embodiment, the connector  894  can be a hollow bolt that extends into and partially through a plate aperture  848 A to provide the desired feed-through for connection of the fluid conduits. 
     As illustrated the connector  894  can be annular-shaped, with a substantially circular cross-section, and having an upper section  894 A and a lower section  894 B that is slightly smaller in outer circumference than the upper section  894 A. Additionally, the plate aperture  848 A can also have a substantially circular cross-section, and have an upper portion  848 B through which the entire connector  894  can fit, and a lower portion  848 C through which only the lower section  894 B of the connector  894  can fit. With this design, the connector  894  can effectively sit on a ledge within the plate aperture  848 A in order to provide the desired feed-through connection with the conduits. 
     In certain embodiments, the orifice of the connector  894  can be sized to regulate the volume and rate of fluid flow between the distribution plates  48 A. In this embodiment, the larger diameter orifices can be used for distribution plates  48 A that are used more and that require more cooling, while smaller diameter orifices are used for distribution plates  48 A that are used less and that require less cooling. Thus, the orifices can be sized to suit the flow (cooling) requirements of the respective distribution plate  48 A. Moreover, the orifices can be sized during the design phase of the mover  18  based on the projected usage of the mover  18  to provide the appropriate flow rate to respective distribution plates  48 A. 
       FIG. 9  is a schematic illustration of a precision assembly, namely an exposure apparatus  934  useful with the present invention. The exposure apparatus  934  includes an apparatus frame  987 , an illumination system  988  (irradiation apparatus), an optical assembly  989  (lens assembly), a reticle stage assembly  990 , a wafer stage assembly  991 , a measurement system  992 , and a control system  993 . The design of the various components of the exposure apparatus  934  can be varied to suit the specific requirements of the exposure apparatus  934 . In certain applications, the various stage assemblies, as described in detail herein, can be used as the wafer stage assembly  991 . Alternatively, with the disclosure provided herein, the stage assemblies provided herein can be modified for use as the reticle stage assembly  990 . 
     The exposure apparatus  934  is particularly useful as a lithographic device that transfers a pattern (not shown) of an integrated circuit from a reticle  994  onto a semiconductor wafer  995 . The exposure apparatus  934  mounts to a mounting base  924 , e.g., the ground, a base, or floor or some other supporting structure. 
     There are a number of different types of lithographic devices. For example, the exposure apparatus  934  can be used as a scanning type photolithography system that exposes the pattern from the reticle  994  onto the wafer  995  with the reticle  994  and the wafer  995  moving synchronously. Alternatively, the exposure apparatus  934  can be a step-and-repeat type photolithography system that exposes the reticle  994  while the reticle  994  and the wafer  995  are stationary. 
     However, the use of the exposure apparatus  934  and stage assemblies provided herein is not limited to a photolithography system for semiconductor manufacturing. The exposure apparatus  934 , for example, can be used as an LCD photolithography system that exposes a liquid crystal display device pattern onto a rectangular glass plate or a photolithography system for manufacturing a thin film magnetic head. Further, the present invention can also be applied to a proximity photolithography system that exposes a mask pattern by closely locating a mask and a substrate without the use of a lens assembly. Additionally, the present invention provided herein can be used in other devices, including other semiconductor processing equipment, elevators, machine tools, metal cutting machines, inspection machines and disk drives. 
     The apparatus frame  987  is rigid and supports the components of the exposure apparatus  934 . The design of the apparatus frame  987  can be varied to suit the design requirements of the rest of the exposure apparatus  934 . The apparatus frame  987  illustrated in  FIG. 9  supports the optical assembly  989 , the reticle stage assembly  990 , the wafer stage assembly  991 , and the illumination system  988  above the mounting base  924 . 
     The illumination system  988  includes an illumination source  996  and an illumination optical assembly  997 . The illumination source  996  emits a beam (irradiation) of light energy. The illumination optical assembly  997  guides the beam of light energy from the illumination source  996  to the optical assembly  989 . The beam of light energy selectively illuminates different portions of the reticle  994  and exposes the wafer  995 . In  FIG. 9 , the illumination source  996  is illustrated as being supported above the reticle stage assembly  990 . Alternatively, the illumination source  996  can be secured to one of the sides of the apparatus frame  987  and the energy beam from the illumination source  996  can be directed to above the reticle stage assembly  990  with the illumination optical assembly  997 . 
     The illumination source  996  can be a g-line source (436 nm), an i-line source (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), a F 2  laser (157 nm), or an EUV source (13.5 nm). Alternatively, the illumination source  996  can generate charged particle beams such as an x-ray or an electron beam. For instance, in the case where an electron beam is used, thermionic emission type lanthanum hexaboride (LaB 6 ) or tantalum (Ta) can be used as a cathode for an electron gun. Furthermore, in the case where an electron beam is used, the structure could be such that either a mask is used or a pattern can be directly formed on a substrate without the use of a mask. 
     The optical assembly  989  projects and/or focuses the light passing through the reticle  994  to the wafer  995 . Depending upon the design of the exposure apparatus  934 , the optical assembly  989  can magnify or reduce the image illuminated on the reticle  994 . The optical assembly  989  need not be limited to a reduction system. It could also be a 1× or magnification system. 
     The reticle stage assembly  990  holds and positions the reticle  994  relative to the optical assembly  989  and the wafer  995 . Similarly, the wafer stage assembly  991  holds and positions the wafer  995  with respect to the projected image of the illuminated portions of the reticle  994 . 
     The measurement system  992  monitors movement of the reticle  994  and the wafer  995  relative to the optical assembly  989  or some other reference. With this information, the control system  993  can control the reticle stage assembly  990  to precisely position the reticle  994  and the wafer stage assembly  991  to precisely position the wafer  995 . For example, the measurement system  992  can utilize multiple laser interferometers, encoders, autofocus systems, and/or other measuring devices. 
     The control system  993  is connected to the reticle stage assembly  990 , the wafer stage assembly  990 , and the measurement system  992 . The control system  993  receives information from the measurement system  992  and controls the stage assemblies  990 ,  991  to precisely position the reticle  994  and the wafer  995 . The control system  993  can include one or more processors and circuits. 
     As described above, a photolithography system according to the above described embodiments can be built by assembling various subsystems, including each element listed in the appended claims, in such a manner that prescribed mechanical accuracy, electrical accuracy, and optical accuracy are maintained. In order to maintain the various accuracies, prior to and following assembly, every optical system is adjusted to achieve its optical accuracy. Similarly, every mechanical system and every electrical system are adjusted to achieve their respective mechanical and electrical accuracies. The process of assembling each subsystem into a photolithography system includes mechanical interfaces, electrical circuit wiring connections and air pressure plumbing connections between each subsystem. Needless to say, there is also a process where each subsystem is assembled prior to assembling a photolithography system from the various subsystems. Once a photolithography system is assembled using the various subsystems, a total adjustment is performed to make sure that accuracy is maintained in the complete photolithography system. Additionally, it is desirable to manufacture an exposure system in a clean room where the temperature and cleanliness are controlled. 
     Semiconductor devices can be fabricated using the above described systems, by the process shown generally in  FIG. 10A . In step  1001  the device&#39;s function and performance characteristics are designed. Next, in step  1002 , a mask (reticle) having a pattern is designed according to the previous designing step, and in a parallel step  1003  a wafer is made from a silicon material. The mask pattern designed in step  1002  is exposed onto the wafer from step  1003  in step  1004  by a photolithography system described hereinabove in accordance with the present invention. In step  1005  the semiconductor device is assembled (including the dicing process, bonding process and packaging process), finally, the device is then inspected in step  1006 . 
       FIG. 10B  illustrates a detailed flowchart example of the above-mentioned step  1004  in the case of fabricating semiconductor devices. In  FIG. 10B , in step  1011  (oxidation step), the wafer surface is oxidized. In step  1012  (CVD step), an insulation film is formed on the wafer surface. In step  1013  (electrode formation step), electrodes are formed on the wafer by vapor deposition. In step  1014  (ion implantation step), ions are implanted in the wafer. The above mentioned steps  1011 - 1014  form the preprocessing steps for wafers during wafer processing, and selection is made at each step according to processing requirements. 
     At each stage of wafer processing, when the above-mentioned preprocessing steps have been completed, the following post-processing steps are implemented. During post-processing, first, in step  1015  (photoresist formation step), photoresist is applied to a wafer. Next, in step  1016  (exposure step), the above-mentioned exposure device is used to transfer the circuit pattern of a mask (reticle) to a wafer. Then in step  1017  (developing step), the exposed wafer is developed, and in step  1018  (etching step), parts other than residual photoresist (exposed material surface) are removed by etching. In step  1019  (photoresist removal step), unnecessary photoresist remaining after etching is removed. 
     Multiple circuit patterns are formed by repetition of these preprocessing and post-processing steps. 
     While a number of exemplary aspects and embodiments of a stage assembly  10  and a fluid distribution network  28  have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.