Abstract:
A robot is provided which comprises (a) a hub ( 311 ) disposed on a substrate ( 306 ); (b) a first motor ( 305 ) which operates a first arm by moving a first magnet ( 305 ) disposed within said hub; (c) a first housing element ( 331 ) for housing said first motor; (d) a first plate ( 321 ) disposed within said hub and attached to a first end of said housing element; and (e) a second plate ( 341 ) attached to a second end of said first housing element such that said substrate extends between said second plate and said hub.

Description:
[0001]    This application claims the benefit of priority from U.S. Provisional Application No. 61/127,446, filed May 12, 2008, having the same title, and having the same inventor, and which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates generally to robots, and more particularly to locking mechanisms for securing the motor of a robot in place. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    The use of robots is widespread in the semiconductor industry, due to their ability to process a large number of semiconductor wafers through many different processing technologies, and to perform repetitive tasks quickly and accurately. The use of robots is especially advantageous in portions of semiconductor fabrication lines where human handling of semiconductor wafers is inefficient or undesirable. For example, many semiconductor fabrication processes, such as etching, deposition, and passivation, occur in reaction chambers having sealed environments. The use of robots allows these environments to be carefully maintained in order to minimize the likelihood of contamination and to optimize processing conditions. 
         [0004]    Modem semiconductor processing systems include cluster tools that integrate a number of process chambers together in order to perform several sequential processing steps without removing the substrate from the highly controlled processing environment. These chambers may include, for example, degas chambers, substrate pre-conditioning chambers, cooldown chambers, transfer chambers, chemical vapor deposition chambers, physical vapor deposition chambers, and etch chambers. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which those chambers are run, are selected to fabricate specific structures using a specific process recipe and process flow. 
         [0005]    Once the cluster tool has been set up with a desired set of chambers and auxiliary equipment for performing certain process steps, the cluster tool will typically process a large number of substrates by continuously passing them, one by one, through a series of chambers or process steps. The process recipes and sequences will typically be programmed into a microprocessor controller that will direct, control and monitor the processing of each substrate through the cluster tool. Once an entire cassette of wafers has been successfully processed through the cluster tool, the cassette may be passed to yet another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing. 
         [0006]    One example of a known fabrication system of the type described above is the cluster tool  101  disclosed in U.S. Pat. No. 6,222,337 (Kroeker et al.), and reproduced in  FIGS. 1-2  herein. The magnetically coupled robots  103 ,  153  disclosed therein are equipped with upper  105  and lower  107  robotic arms having a frog-leg type construction that are adapted to provide both radial and rotational movement of the robot blade  109  within a fixed plane. The radial and rotational movements can be coordinated or combined to allow for pickup, transfer and delivery of substrates from one location within the cluster tool to another location. For example, the robotic arm may be used to move substrates from one processing chamber to an adjacent chamber. 
         [0007]      FIG. 1  is a schematic diagram of the integrated cluster tool  101  of Kroeker et al. Wafers or other substrates  102  are introduced into, and withdrawn from, the cluster tool  101  through a cassette loadlock  111 . A robot  103  having a blade  109  is located within a chamber  113  of the cluster tool  101  and is adapted to transfer the substrates from one process chamber to another. These process chambers may include, for example, a cassette loadlock  115 , a degas wafer orientation chamber  117 , a preclean chamber  119 , a PVD TiN chamber  121  and a cooldown chamber  123 . The robot blade  109  is illustrated in the retracted position in which it can rotate freely within the chamber  113 . 
         [0008]    A second robot  153  is located in transfer chamber  163 , and is adapted to transfer substrates between various chambers which may include, for example, a cooldown chamber  165 , a preclean chamber  167 , a CVD Al chamber  169  and a PVD AlCu processing chamber  171 . The specific configuration of chambers illustrated in  FIG. 1  is designed to provide an integrated processing system capable of both CVD and PVD processes in a single cluster tool. A microprocessor controller  171  is provided to control the fabricating process sequence, conditions within the cluster tool, and the operation of the robots  103 ,  153 . 
         [0009]    Robots of the type depicted in  FIGS. 1-2  above are utilized, for example, in the ENDURA® and CENTURA® 200 nm/300 nm platforms sold by Applied Materials (Santa Clara, Calif.). As seen in  FIG. 2 , these robots  103  include a central hub  131 , a pair of upper arms  105 , and a pair of lower arms  107 . The lower arms  107  are rotatingly attached to the hub  131  and are driven by servo drives housed within the hub  103 . 
       SUMMARY OF THE DISCLOSURE 
       [0010]    In one aspect, a robot is provided which comprises (a) a hub disposed on a substrate; (b) a first motor which operates a first arm by moving a first magnet disposed within said hub; (c) a first housing element for housing said first motor; (d) a first plate disposed within said hub and attached to a first end of said housing element; and (e) a second plate attached to a second end of said first housing element such that said substrate extends between said second plate and said hub. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein: 
           [0012]      FIG. 1  is an illustration of a prior art cluster tool. 
           [0013]      FIG. 2  is an illustration of a prior art robot. 
           [0014]      FIG. 3  is an illustration, partially in section, of a prior art robot. 
           [0015]      FIG. 4  is a top view of the robot of  FIG. 3 . 
           [0016]      FIG. 5  is a side view, partially in section, of the robot of  FIG. 3 . 
           [0017]      FIG. 6  is an enlarged view of the hub and magnetic ring of the robot of  FIG. 3 . 
           [0018]      FIG. 7  is an enlarged view of the motor and magnetic plate of the robot of  FIG. 3 . 
           [0019]      FIG. 8  is an illustration, partially in section, of one particular, non-limiting embodiment of a robot made in accordance with the teachings herein. 
           [0020]      FIG. 9  is an enlarged view of the motor and magnetic plate of the robot of  FIG. 8 . 
           [0021]      FIG. 10  is an enlarged view of the mounting assembly of the robot if  FIG. 8 . 
           [0022]      FIG. 11  is an enlarged view of the first housing element of the robot if  FIG. 8 . 
           [0023]      FIG. 12  is a top view of the first housing element of  FIG. 11 . 
           [0024]      FIG. 13  is a side view of the second plate of the robot if  FIG. 8 . 
           [0025]      FIG. 14  is a side view of the second plate of the robot if  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    While the robots depicted in  FIGS. 1-2  have some advantageous features, they also suffer from some infirmities. In particular, the design of these robots features a motor which is held in place by loose fitting contact positions created by the original equipment manufacturer. Because these contact positions are loose, they tend to wear over time, which causes the rotating motor assembly to position inaccurately. 
         [0027]    In addition, these robots have an error associated with their operation which arises when the motor assembly “hops” out of its mounting position due to motor torque as a result of the aforementioned loose fitting connections. This hopping action can cause a jamming of the rotating motor magnetic plate inside of the hub of the device. When this occurs, the rotation of the motor is inhibited, thus resulting in a condition in which the motor “commanded to position” counts will not equal the motor “encoder counts”. When such a state is achieved, a systems fault results which shuts down the motor. 
         [0028]    It has now been found that the foregoing problems may be addressed through the provision of a device that secures or locks down the motor assembly of the servo drive on such a robot (the robot may be, for example, the single arm robot known as the HP Robotic Arm). A device of this type may be utilized to improve the positional accuracy of the rotating motor assembly by tightening the original equipment manufacturer contact positions. Moreover, a device of this type may be utilized to prevent the motor assembly from hopping out of its mounting position due to loose fitting connections when it is subject to motor torque. 
         [0029]    The devices and methodologies disclosed herein may be further understood with reference to the attached drawings. For the sake of simplicity, this explanation focuses on the lower motor of an HP Robotic Arm and its associated mount. However, it will be appreciated that a robotic assembly may have two or more such motors, and that the devices and methodologies described herein may be applied to any, or all, of these motors to enhance operational performance. It will further be appreciated that these devices and methodologies may be applied to various other robot systems as well. 
         [0030]    The function of the lower motor assembly  201  may be further appreciated with reference to  FIGS. 3-4 , which depict, respectively, a top view and side view (partially in cross-section) of the lower motor assembly  201  of a prior art robot. The motor  203  within this assembly  201  has a rotating shaft  207  with a magnetic plate  205  connected thereto. A complimentary magnetic ring  209  is located in the vacuum area of the assembly  201 . A wall  211 , referred to as the “soup bowl”, is disposed between the two sets of magnets. 
         [0031]    In operation, the motor  203  rotates the magnetic plate  205 , and the complimentary vacuum magnetic ring  209  rotates at the same time and at the same speed. One side of the robotic frog arm (which includes one upper arm  105  and one lower arm  107 ; see  FIG. 2 ) is attached to the lower rotating vacuum magnetic ring  209 . The second motor assembly, known as the top motor assembly, is not shown here but has the second side of the robotic frog arm (which includes the other upper arm  105  and lower arm  107 ; see  FIG. 2 ) attached to it. The frog arm  103  (see  FIG. 2 ) extends when the lower motor  203  rotates clockwise while the upper motor (not shown) rotates counter clockwise. Retraction is accomplished by rotating in the opposite directions. Theta motions (i.e., rotation of the robot) occur when both motors rotate in the same directions. 
         [0032]    An example of the motor mount utilized in prior art motor mount assemblies is depicted in  FIGS. 3-7 . The assembly  201  shown therein utilizes a motor mount which comprises a thin plate  221  attached to the motor  203  and which has three dowel pins  223  extending from it. As seen in  FIG. 5 , these dowel pins  223  are utilized to register the lower motor assembly  203  to the soup bowl  211 . In particular, the motor  203  is lowered into the soup bowl  211  such that the three dowel pins  223  are inserted into three corresponding holes  224  located in the bottom of the soup bowl. As seen in  FIG. 3 , the soup bowl  211  is attached to a substrate  206  which is typically the bottom of a cluster tools chamber. 
         [0033]    It has now been found that there is an error in repeatability due to the way the lower motor  203  is mounted inside the soup bowl  211  in the prior art device of  FIGS. 3-7 . In particular, this connection is loose, thus permitting a certain amount of mechanical backlash. This backlash may be quantified as the distance one can rotate the arm  103 , while the motor  203  is enabled, and measure a side to side motion. This backlash represents a mechanical error that the motor cannot compensate for, and thus gives rise to an inability on the part of the robot to accurately repeat an extension position. 
         [0034]    A second type of error arises from motor torque. When this torque occurs, the entire motor assembly hops out of its location, and the rotating magnetic plate  205  jams inside of the soup bowl  211 . This situation creates an unrecoverable error which is unacceptable to users of the robot. 
         [0035]    In order to remedy the foregoing problems, devices and methodologies are described herein which utilize a mount which is adapted to lock the motor of a robotic arm into place, thereby reducing or eliminating the backlash and motor torque that gives rise to placement errors. In the preferred embodiment of these devices and methodologies, the mounting plate  221  of the prior art (see  FIG. 7 ) is replaced with a two-piece replacement mount that sandwiches the bottom portion of the soup bowl  211  and the substrate  206  between them, thereby locking the motor assembly into place. As explained in further detail below, the second plate of the mount may be attached to the bottom of the cluster tool so that, when the bottom plate is bolted to the mount, the two pieces sandwich the chamber floor between them, thereby creating a secure mounting condition for the entire motor assembly. In addition, one or more set screws may be provided for added security against lateral motion. 
         [0036]    The devices and methodologies disclosed herein may be further appreciated with respect to the particular, non-limiting embodiment depicted in  FIGS. 8-14 . As with the prior art assembly depicted in  FIGS. 3-7 , the motor mount assembly  301  depicted therein comprises a thin plate  321  (see  FIG. 9 ) attached to the motor  303  which has three dowel pins  323  extending from it. As seen in  FIG. 8 , these dowel pins  323  are utilized to register the lower motor assembly  303  to the soup bowl  311 . In particular, the motor  303  is lowered into the soup bowl  311  in such a way that the three dowel pins  323  are inserted into three corresponding holes  324  located in the bottom of the soup bowl  311 . As seen in  FIG. 8 , the soup bowl  311  is attached to a substrate  306  which is typically the bottom of a cluster tools chamber. 
         [0037]    Unlike the prior art assembly depicted in  FIGS. 3-7 , however, the motor mount assembly  301  depicted in  FIGS. 8-14  comprises a two-piece mount which, in addition to upper plate  321 , also comprises a lower plate  341  (shown in greater detail in  FIG. 14 ) which is disposed between the upper  331  and lower  333  portions of the motor assembly  303  (see, e.g.,  FIG. 9 ) and which is attached to the bottom of the cluster tool. As seen in  FIG. 8 , the bottom portion of the soup bowl  311  and the substrate  306  (typically the chamber floor) are sandwiched between the upper  321  and lower  341  plates, thereby securely locking the motor mount assembly  301  into place and eliminating the sources of error noted above which arise from motor torque and backlash. 
         [0038]    With reference to  FIG. 14 , the lower plate  341  has a central opening  365  through which the motor assembly  303  extends. The lower plate  341  further comprises first  361  and second  363  sets of apertures. The first set of apertures  361  accommodate a set of bolts  343  (see  FIG. 9 ) which bound the upper portion  331  of the motor assembly to the substrate  341 . The second set of apertures  363  accommodate a series of set screws which may be provided in some embodiments for added security against lateral motion. 
         [0039]    The above description of the present invention is illustrative, and is not intended to be limiting. It will thus be appreciated that various additions, substitutions and modifications may be made to the above described embodiments without departing from the scope of the present invention. Accordingly, the scope of the present invention should be construed in reference to the appended claims.