Abstract:
A robotic hub assembly is provided which comprises a spacer configuration ( 101 ) that includes first ( 103 ) and second ( 105 ) spacers disposed in opposing relation to each other, and a device, such as a pin ( 111 ), for restricting the relative motion of the first and second spacers in a lateral direction.

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention pertains generally to wafer processing equipment, and more particularly, to end effectors for such equipment.  
       BACKGROUND OF THE INVENTION  
       [0002]     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.  
         [0003]     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.  
         [0004]     One example of a fabrication system is the cluster tool disclosed in U.S. Pat. No. 6,222,337 (Kroeker et al.), and reproduced in  FIGS. 1 and 2  herein. The magnetically coupled robot disclosed therein comprises a frog-leg type connection or arms between the magnetic clamps and the wafer blade to provide both radial and rotational movement of the robot blade within a fixed plane. Radial and rotational movements can be coordinated or combined in order to pickup, transfer and deliver substrates from one location within the cluster tool to another, such as from one chamber to an adjacent chamber.  
         [0005]      FIG. 1  is a schematic diagram of the integrated cluster tool  10  of Kroeker et al. Substrates are introduced into and withdrawn from the cluster tool  10  through a cassette loadlock  12 . A robot  14  having a blade  17  is located within the cluster tool  10  to transfer the substrates from one process chamber to another, for example cassette loadlock  12 , degas wafer orientation chamber  20 , preclean chamber  24 , PVD TiN chamber  22  and cooldown chamber  26 . The robot blade  17  is illustrated in the retracted position for rotating freely within the chamber  18 .  
         [0006]     A second robot  28  is located in transfer chamber  30  to transfer substrates between various chambers, such as the cooldown chamber  26 , preclean chamber  24 , CVD A 1  chamber (not shown) and a PVD A 1 Cu processing chamber (not shown). The specific configuration of the chambers illustrated in  FIG. 1  comprises an integrated processing system capable of both CVD and PVD processes in a single cluster tool. A microprocessor controller  29  is provided to control the fabricating process sequence, conditions within the cluster tool, and the operation of the robots  14 ,  28 .  
         [0007]      FIG. 2  is a schematic view of the magnetically coupled robot of  FIG. 1  shown in both the retracted and extended positions. The robot  14  (see  FIG. 1 ) includes a first strut  81  rigidly attached to a first magnet clamp  80  and a second strut  82  rigidly attached to a second magnet clamp  80 ′. A third strut  83  is attached by a pivot  84  to strut  81  and by a pivot  85  to a wafer blade  86 . A fourth strut  87  is attached by a pivot  88  to strut  82  and by a pivot  89  to wafer blade  86 . The structure of struts  81 - 83 ,  87  and pivots  84 ,  85 ,  88 , and  89  form a “frog leg” type connection of wafer blade  86  to magnet clamps  80 , 80 ′.  
         [0008]     When magnet clamps  80 , 80 ′ rotate in the same direction with the same angular velocity, then the robot also rotates about axis x in this same direction with the same velocity. When magnet clamps  80 ,  80 ′ rotate in opposite directions with the same absolute angular velocity, then there is no rotation of assembly  14 , but instead there is linear radial movement of wafer blade  86  to a position illustrated by dashed elements  81 ′- 89 ′.  
         [0009]     A wafer  35  is shown being loaded on wafer blade  86  to illustrate that the wafer blade can be extended through a wafer transfer slot  810  in a wall  811  of a chamber  32  to transfer such a wafer into or out of the chamber  32 . The mode in which both motors rotate in the same direction at the same speed can be used to rotate the robot from a position suitable for wafer exchange with one of the adjacent chambers  12 ,  20 ,  22 ,  24 ,  26  (see  FIG. 1 ) to a position suitable for wafer exchange with another of these chambers. The mode in which both motors rotate with the same speed in opposite directions is then used to extend the wafer blade into one of these chambers and then extract it from that chamber. Some other combination of motor rotation can be used to extend or retract the wafer blade as the robot is being rotated about axis x.  
         [0010]     To keep wafer blade  86  directed radially away from the rotation axes x, an interlocking mechanism is used between the pivots or cams  85 ,  89  to assure an equal and opposite angular rotation of each pivot. The interlocking mechanism may take on many designs. One possible interlocking mechanism is a pair of intermeshed gears  92  and  93  formed on the pivots  85  and  89 . These gears are loosely meshed to minimize particulate generation by these gears. To eliminate play between these two gears because of this loose mesh, a weak spring  94  (see  FIG. 4 ) may be extended between a point  95  on one gear to a point  96  on the other gear such that the spring tension lightly rotates these two gears in opposite directions until light contact between these gears is produced.  
         [0011]     Although robots of the type depicted in U.S. Pat. No. 6,222,337 (Kroeker et al.) have some desirable properties, robots of this type also have some shortcomings. In particular, it has been found that robots of this type often suffer excessive wear in the hub assembly  14  and in the wrist  85 ′,  89 ′ and elbow  84 ′,  88 ′ joints, and exhibit deviations from parallelism between the opposing arms. These problems result in excessive maintenance requirements and in deviations in the manufacturing process. There is thus a need in the art for a robotic assembly which overcomes these infirmities, and for a method for making the same. These and other needs are met by the devices and methodologies disclosed herein and hereinafter described.  
       SUMMARY OF THE INVENTION  
       [0012]     In one aspect, a robotic hub assembly is provided which comprises first and second spacers disposed in opposing relation to each other, and a device, such as a plurality of pins, for restricting the relative motion of the first and second spacers in a lateral direction. The device preferably comprises first and second sets of pins which extend through the first and second spacers. Preferably, the first set of pins extend through holes in the first spacer and rotatingly engage threaded apertures provided in said second spacer, and the second set of pins extend through holes in said second spacer and rotatingly engage threaded apertures provided in said first spacer.  
         [0013]     One skilled in the art will appreciate that the various aspects of the present disclosure may be used in various combinations and sub-combinations, and each of those combinations and sub-combinations is to be treated as if specifically set forth herein.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     For a more complete understanding of the present invention 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:  
         [0015]      FIG. 1  is an illustration of a cluster tool equipped with a robotic wafer handling system;  
         [0016]      FIG. 2  is an illustration of the arm assembly of the robot depicted in  FIG. 1 , and illustrates the retracted and extended positions of the arm assembly;  
         [0017]      FIG. 3  is an illustration of the wrist assembly of the robot depicted in  FIG. 1 ;  
         [0018]      FIG. 4  is an illustration of a prior art robotic arm assembly and illustrates the retracted and extended positions of the arm assembly;  
         [0019]      FIG. 5  is a side view, partially in section, of a spacer configuration made in accordance with the teachings herein; and  
         [0020]      FIG. 6  is a side view of the spacer configuration of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The aforementioned needs are met by the devices and methodologies disclosed herein. In particular, after careful investigation, it has now been found that, in conventional robotic arms of the type illustrated in  FIGS. 1-4 , the hub assembly can undergo nutation (that is, it can move out of concentricity with its piece parts) and force the lower arm to roll away from the rotating hub axis. For example, in such a configuration, the hub contains two halves, each of which is attached to one of the arms, and these halves are separated by opposing spacers. In use, these spacers can deviate from concentricity, thus causing the aforementioned roll.  
         [0022]     In a frog-leg construction such as that depicted in  FIGS. 1-4 , this roll is transferred along the beam of the lower arm such that the arm is now out of parallelism with the second half of the frog arm. This condition induces stress within the wrist, elbow and hub assemblies, causing premature wear and adding abnormal motions in the z-direction (the direction perpendicular to the plane in which the arms extend and retract) as the arm is in motion. The devices and methodologies disclosed herein provide a means for eliminating this roll, thus preventing such premature wear and allowing the robotic arm to operate properly.  
         [0023]      FIGS. 5 and 6  illustrate one non-limiting embodiment of a spacer configuration  101  for a robotic hub made in accordance with the teachings herein. Some of the details of the spacer configuration have been eliminated for simplicity of illustration. The spacer configuration shown therein comprises first  103  and second  105  opposing spacers which are spaced apart from each other by a predetermined distance.  
         [0024]     In a completed hub assembly, the first  103  and second  105  spacers are disposed between first and second bearing rings (not shown), and one arm of the robot is attached to each bearing ring. The spacers  103 ,  105  maintain the first and second bearing rings (not shown) in a proper orientation with respect to each other. The first and second bearing rings rotate in the same direction when the robotic arms (not shown) are to be moved in a lateral direction, and rotate in opposing directions when the robotic arms are to be extended or retracted.  
         [0025]     As noted above, in hub assemblies of the prior art which contain spacer configurations somewhat similar in design to the configuration depicted in  FIGS. 5 and 6 , the two spacers often deviate from concentricity. This frequently happens, for example, when the two bearing rings rotate in opposite directions, and the resulting force pulls the spacers away from concentricity. This causes the hub to undergo nutation, which places stress on the bearings inside the hub and causes premature wear.  
         [0026]     The spacer configuration  101  depicted in  FIGS. 5 and 6  is adapted to eliminate such nutation by stiffening the hub assembly. This configuration  101  utilizes a series of pins  111  to stiffen the spacer configuration, thereby eliminating lateral motion and maintaining the first  103  and second  105  spacers in a concentric relation to each other.  
         [0027]     The through holes  113  for the pins in the spacers are constructed such that the pins can move in a vertical direction, but are restricted in their motion in the lateral direction. In one particular embodiment, for example, the pins are 18/8 hardened steel pins, and the through holes are designed to permit motion of less than about 0.001 inches in the lateral direction.  
         [0028]     The pins may be disposed in various manners throughout the spacers. Preferably, however, four pins are utilized, with the pins being spaced 90° apart. It is also preferred that the pins are arranged in pairs such that the pairs are facing opposing directions, and such that each of the pins in the pair are disposed on opposite sides of a spacer.  
         [0029]     Although the present invention is described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention.