Abstract:
A robot is provided which comprises a wafer blade ( 105 ) having a pocket ( 109 ) therein for receiving a semiconductor wafer, and a retractable protrusion ( 107 ) which is movable from a first position in which said protrusion prevents the removal of said wafer from said pocket, to a second position in which said protrusion permits the removal of said wafer from said pocket.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Ser. No. 61/137,416, entitled “Edge Grip End Effector”, which was filed on Jul. 30, 2008, and which is incorporated herein by reference in its entirety; and to U.S. Ser. No. 61/118,755, entitled “Edge Grip End Effector”, which was filed on Dec. 1, 2008, 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 robots equipped with mechanisms for securing a wafer within an end effector. 
       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]    Modern 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, cool-down 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 cool-down chamber  165 , a pre-clean 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 wafer blade having a pocket therein for receiving a semiconductor wafer; and at least one retractable protrusion which is movable from a first position in which said protrusion prevents the removal of said wafer from said pocket, to a second position in which said protrusion permits the removal of said wafer from said pocket. 
         [0011]    In another aspect, an end effector is provided which comprises a wafer blade having a pocket therein for receiving a semiconductor wafer; and a retractable protrusion which is movable from a first position in which it secures said wafer in said pocket, to a second position in which said wafer is removable from said pocket. 
         [0012]    In a further aspect, a robot is provided which comprises (a) a robotic arm which extends along a path including first, second and third points, wherein said arm is in a relatively retracted position at said first point and is in a relatively extended position at said third point, and wherein said second point is disposed between said first and third points; (b) an end effector which is attached to said arm; and (c) a mechanical actuator disposed in said end effector, said actuator assuming a first state when said robotic arm is at said first point, and assuming a second state when said robotic arm is at said second point. 
         [0013]    In still another aspect, a robot is provided which comprises (a) a robotic arm which extends along a path including first, second and third points; (b) an end effector which is attached to said arm; and (c) a mechanical actuator disposed in said end effector, said actuator assuming a first state when said robotic arm is at said first point, and assuming a second state when said robotic arm is at said second point; wherein said arm is in a more retracted position when it is at said first point compared to when it is at said third point, wherein said second point is disposed between said first and third points. 
         [0014]    In a further aspect, a robot is provided which comprises (a) a robotic arm which is extendible to assume at least first, second and third positions, wherein said arm is more extended when it is in the second position relative to the first position, and wherein said arm is more extended when it is in the third position relative to the second position; (b) an end effector which is attached to said arm; and (c) a mechanical actuator disposed in said end effector, said actuator assuming a first state when said robotic arm is in said first position, and assuming a second state when said robotic arm is in said second position. 
         [0015]    In yet another aspect, a robot is provided which comprises (a) a hub; (b) a robotic arm which is extendible from said hub to assume at least first, second and third positions, wherein said arm is more extended when it is in the second position relative to the first position, and wherein said arm is more extended when it is in the third position relative to the second position; (c) an end effector which is attached to said arm; and (d) a mechanical actuator disposed in said end effector, said actuator assuming a first state when said robotic arm is in said first position, and assuming a second state when said robotic arm is in said second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    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: 
           [0017]      FIG. 1  is an illustration of a prior art cluster tool. 
           [0018]      FIG. 2  is an illustration of a prior art robot. 
           [0019]      FIG. 3  is an illustration of a first particular, non-limiting embodiment of a wrist assembly made in accordance with the teachings herein, showing the upper slide in a disengaged position and the wafer hold finger in an engaged position. 
           [0020]      FIG. 4  is an illustration of the wrist assembly of  FIG. 3 , showing the upper slide in an engaged position, and the wafer hold finger in a disengaged position. 
           [0021]      FIG. 5  is an illustration of the wrist assembly of  FIG. 3 , in which the wrist assembly has been partially disassembled to show the details of the rack and pinion system. 
           [0022]      FIG. 6  is an illustration of the upper rack and slide of the wrist assembly of  FIG. 3 , with the cover removed and the wafer hold finger in a retracted position. 
           [0023]      FIG. 7  is an illustration of the upper rack and slide of the wrist assembly of  FIG. 3 , with the cover removed and the wafer hold finger in an engaged position. 
           [0024]      FIG. 8  is an illustration of the wrist assembly of  FIG. 3  showing the location of the pinion. 
           [0025]      FIG. 9  is an illustration of the wrist plate of the wrist assembly of  FIG. 3 . 
           [0026]      FIG. 10  is an illustration of the components of the rack and pinion system of the wrist assembly of  FIG. 3 . 
           [0027]      FIG. 11  is an illustration of a wafer blade and wrist assembly incorporating the wrist assembly of  FIG. 3 , and showing the wafer hold finger in a retracted position (in this position, the plunger is forced inward by the forearm making contact where my thumb is). 
           [0028]      FIG. 12  is an illustration of a wafer blade and wrist assembly incorporating the wrist assembly of  FIG. 3 , and showing the wafer hold finger in an engaged position (in this position, plunger is in the outward direction, making contact with the wafer). 
           [0029]      FIG. 13  is an illustration of the wafer blade from the assembly of  FIG. 12 . 
           [0030]      FIG. 14  is a magnified view of REGION  14  of  FIG. 13 . 
           [0031]      FIG. 15  is a top view of the upper rack and slide of the wrist assembly of  FIG. 3 . 
           [0032]      FIG. 16  is a bottom view of the upper rack and slide of the wrist assembly of  FIG. 3 . 
           [0033]      FIG. 17  is an illustration of some of the components of a rack and pinion system utilized in some of the devices described herein. 
           [0034]      FIG. 18  is an illustration of a wrist assembly of a robotic arm made in accordance with the teachings herein, shown with a cover plate removed and with the arms in a retracted position. 
           [0035]      FIG. 19  is an illustration of a wrist assembly of a robotic arm made in accordance with the teachings herein, shown with a cover plate removed and with the arms in an extended position. 
           [0036]      FIG. 20  is a bottom view of  FIG. 18 . 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    While the robots depicted in  FIGS. 1-2  have some advantageous features, they also suffer from some infirmities. In particular, as semiconductor processing speeds have increased, it has become increasingly difficult for robots of this type to maintain the semiconductor wafer in a proper position within the pocket of the wafer blade. 
         [0038]    It has now been found that the foregoing problem may be addressed through the provision of a robot (or an end effector thereof) which is equipped with a wafer holding means for preventing a wafer from moving inside of a wafer blade pocket while the robot is moving at higher speeds. Preferably, the wafer holding means can be deactivated when the robot is moving at slower speeds, or when removal of the wafer blade from the wafer blade pocket is desired. 
         [0039]    In one preferred embodiment, for example, the wafer holding means is in the form of a finger which engages a wafer disposed in the wafer blade pocket while the wafer blade is moving at higher speeds. In this particular embodiment, the finger disengages the wafer when, and only when, the arms of the robot are extended a predefined distance k, where k is typically chosen to be sufficiently large such that, when k is reached, the wafer is nearing its target and/or the wafer blade is moving at a slower speed. The wafer blade is preferably fitted with a plurality of elastomeric pads and/or a plurality of elastomeric posts so that, at such slower speeds, the wafer is prevented from moving within the wafer blade pocket even when the finger is disengaged. 
         [0040]    The devices and methodologies disclosed herein may be further understood with reference to the first particular, non-limiting embodiment, depicted in  FIGS. 3-20 , of a robot and its associated end effector made in accordance with the teachings herein. As seen in  FIGS. 11-12 , an end effector assembly  101  is provided which includes a wrist assembly  103  and a wafer blade  105 . The wrist assembly  103  is equipped with a protrusion  107  which, in the present embodiment, is essentially cylindrical in shape. The protrusion  107 , which may comprise a metal and/or elastomeric material, extends into a circular wafer pocket  109  or depression provided in the surface of the wafer blade  105 . 
         [0041]    The protrusion  107  in the particular embodiment depicted is driven by a rack-and-pinion system  111  which is housed within the wrist assembly  103 . The rack-and-pinion system  111  moves the protrusion  107  between an extended position, as shown in  FIGS. 11 and 18 , and a retracted position, as shown in  FIGS. 12 and 20 . Although the difference in the amount by which the protrusion  107  moves in going from a retracted position to an extended position is typically small, the force exerted upon the wafer when the protrusion  107  is in the extended position is sufficiently high to secure the wafer within the wafer pocket  109  when the wafer blade  105  is moving at high speeds. As explained in greater detail below, in a preferred embodiment, the robotic arm is mechanically adapted such that the finger engages the wafer when the wafer blade is moving at higher speeds, and disengages the wafer as the arm extends and nears its target. 
         [0042]    The wrist assembly  103  (with cover plate removed) is shown in greater detail in  FIGS. 3 ,  4  and  18 - 20 . As seen therein, the rack-and-pinion system  111  serves to move the protrusion  107  from a first position in which the protrusion  107  prevents the removal of a wafer (not shown) from the wafer blade pocket  109  (see  FIGS. 12 ,  18  and  20 ), to a second position in which the protrusion  107  permits the removal of the wafer from the pocket  109  (see  FIGS. 11 and 19 ). Preferably, this is accomplished by moving the protrusion  107  axially along a diameter of the wafer pocket  109  so that the protrusion  107  engages a wafer disposed in the pocket  109  when the protrusion  107  is in the first position, and disengages the wafer when it is moved into the second position. 
         [0043]      FIGS. 5-10  show the details of the rack-and-pinion system  111 . With reference to  FIG. 5 , the wrist assembly  103  is shown with the lower rack  121  and cover plate  131  removed to reveal the details thereof, including the protrusion  107 .  FIG. 6  shows the upper rack  123  (with the cover removed) with the protrusion  107  in the retracted position.  FIG. 7  shows the upper rack  123  (with the cover removed) with the protrusion  107  in the extended position. 
         [0044]    In one possible configuration of a robot made in accordance with the teachings herein, the end effector assembly  101  of  FIG. 3  is mounted on first  151  and second  153  robotic arms as shown in  FIGS. 18-20 . In operation, as the robotic arms  151 ,  153  extend, plates  157  and  159  rotate in a counterclockwise manner to engage the upper rack  123  of the rack-and-pinion system  111 . Since the upper rack  123  is in communication with the lower rack  121  by way of a pinion  125  (see  FIG. 10 ), the upper  123  and lower  121  racks move in opposite directions. Hence, since the lower rack has protrusion  107  mounted thereon, as the plates  157 ,  159  press against the upper rack  123 , the protrusion  107  retreats. Conversely, as the arms  151 ,  153  retract, the plates  157 ,  159  are withdrawn from the upper rack  123  (see  FIGS. 6-7 ). Since an internal spring  161  is attached to the upper rack  123 , as the plates  157  and  159  are withdrawn from the upper rack  123 , the upper rack  123  pulls back, thus causing the protrusion  107  to extend into the wafer pocket  109 . The spring  161  is preferably equipped with one or more set screws which allow the tension of the spring to be adjusted. 
         [0045]      FIGS. 8-10  illustrate further details of the design of the wrist assembly. Thus,  FIG. 8  shows a bottom view of the wrist assembly  103  with the lower  121  and upper  123  racks removed to reveal the pinion gear  125 .  FIG. 9  shows the wrist assembly  103  alone.  FIG. 10  shows some of the components of the wrist assembly  103 . These include the pinion gear  125 , the right axle  127 , the left axle  129 , the upper rack  123 , the lower rack  121 , the cover plate  131 , and a plurality of fasteners  133 . 
         [0046]      FIGS. 13-14  depict the wafer blade  105  in greater detail. The wafer blade  105  in the particular embodiment depicted is machined from  6061  aluminum which is hard-coated with aluminum oxide. The aluminum oxide minimizes particle formation in the event of wafer-to-metal contact. The wafer blade  105  is equipped with a (preferably circular) pocket  109  on the surface thereof which is adapted to hold a complimentary-shaped wafer (not shown). The circular pocket  109  is provided with high temperature elastomeric O-rings  143  which support a wafer above the surface of the wafer blade  105  to ensure a clean, particle-free environment. The O-rings  143  may comprise an elastomeric material, such as a perfluoroelastomer. The combination of the O-rings  143 , the wafer pocket  109  and elastomeric posts  173  (described below) permits the protrusion  107  to disengage the wafer as the arms  151 ,  153  approach the end of their extension, without risking movement of the wafer at the slower speeds encountered there. 
         [0047]    The wafer pocket  109  is defined by opposing sidewalls  147  and  149 . Sidewall  147  is equipped with a notch  151  which permits the protrusion  107  (see  FIGS. 3-4 ) to extend therethrough. Sidewall  149  (shown in greater detail in  FIG. 14 ) is equipped with two elastomeric posts  173  which are generally rod-shaped and which protrude about 0.012 to about 0.015 inches into the pocket  141 . Protrusion  107  (see  FIGS. 3-4 ) is of a similar construction and also protrudes about 0.012 to about 0.015 inches into the pocket  141 . 
         [0048]    The use of elastomeric posts  173  in combination with protrusion  107  to grip the wafer allows the protrusion  107  to press against the wafer with greater force than would be the case if the wafer were being pressed against a rigid surface. Moreover, this force is adjustable by virtue of spring  161 . This arrangement maintains the wafer in the pocket while the protrusion is extended and prevents damage to the wafer which might otherwise result from the clamping force. The wafer is also engaged and disengaged much more slowly than pneumatic clamps of the type used in the prior art, thus preventing damage to the wafer from “knocking”. As a further benefit, the wafer is gripped from at least three points along its edges. Since the wafer typically has the greatest momentum along an axis parallel to its major surfaces when the wafer blade is in motion, this arrangement minimizes the force required to maintain the wafer in the wafer blade pocket. 
         [0049]    One advantage of the foregoing embodiment is that the wrist assembly can be configured so that the point at which the finger  107  engages the wafer can be adjusted over a wide range. This allows the robot to accommodate a wide variety of tool settings. In a cluster tool, where the robotic arm may have to interact with several chambers, this point may be set in reference to the closest chamber (that is, the chamber requiring the least extension of the robotic arm). By contrast, conventional robots equipped with actuating mechanisms typically have fixed set points, and thus cannot accommodate a need for changes in the set point. 
         [0050]    It will be appreciated that the devices and methodologies disclosed herein may be utilized for other purposes besides maintaining wafers within a wafer pocket. For example, in many retrofit applications involving existing robots, it is desirable to add functionality to the robot. However, such modifications are often constrained by available assets. For example, it may be challenging to retrofit a robotic arm with a pneumatic tool if the robotic arm lacks wiring or other means to control the tool. However, the approach described herein may be utilized to mechanically activate the tool when the robotic arm is extended a certain distance (or range of distances). For example, a rack and pinion system of the type described above may be used in such a robot as a mechanical actuator to move the tool between a first and second state which may be, for example, an “on” state and an “off” state. 
         [0051]    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.