Abstract:
A rotary chuck for processing wafer-shaped articles comprises a chuck body having a series of gripping pins that are movable by sliding horizontally and in unison relative to the chuck body from a first position in which the gripping pins are relatively more retracted into the chuck body to a second position in which the gripping pins are relatively more extended from the chuck body and in which the gripping pins are positioned so as to support a wafer-shaped article of a predetermined diameter.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to an apparatus for treating surfaces of wafer-shaped articles, such as semiconductor wafers. 
         [0003]    2. Description of Related Art 
         [0004]    Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668. 
         [0005]    Alternatively, a chuck in the form of a ring rotor adapted to support a wafer may be located within a closed process chamber and driven without physical contact through an active magnetic bearing, as is described for example in U.S. Pat. No. 8,490,634. 
         [0006]    For chucks of the type described in U.S. Pat. No. 8,490,634, the chuck body overlies a peripheral region of the wafer, such that for some processes this region cannot be adequately treated. U.S. Pat. No. 5,845,662 discloses a ring-shaped chuck that does not significantly overlap a supported wafer, but a basket-like configuration of pivotable or flexible fingers is required, which keeps the wafer spaced axially apart from the ring-shaped chuck, and increases the size and complexity of the device. 
       SUMMARY OF THE INVENTION 
       [0007]    In one aspect, the present invention relates to a rotary chuck for processing wafer-shaped articles, comprising a chuck body having a series of gripping pins that are movable by sliding horizontally and in unison relative to the chuck body from a first position in which the gripping pins are relatively more retracted into the chuck body to a second position in which the gripping pins are relatively more extended from the chuck body and in which the gripping pins are positioned so as to support a wafer-shaped article of a predetermined diameter. 
         [0008]    In preferred embodiments of the rotary chuck according to the present invention, each of the gripping pins comprises a proximal part mounted within the chuck body and a distal part that projects outwardly from the chuck body, the distal part sliding through a respective opening in the chuck body during movement between the first and second positions. 
         [0009]    In preferred embodiments of the rotary chuck according to the present invention, the distal parts slide horizontally through the respective openings toward a center of the chuck body during movement from the first position to the second position. 
         [0010]    In preferred embodiments of the rotary chuck according to the present invention, each of the distal parts comprises a respective distal end configured to contact and support a peripheral edge of a wafer-shaped article when held by the rotary chuck, and wherein the distal ends face one another in the first and second positions of the series of gripping pins. 
         [0011]    In preferred embodiments of the rotary chuck according to the present invention, each of the distal ends comprises a horizontal notch. 
         [0012]    In preferred embodiments of the rotary chuck according to the present invention, the chuck body is ring-shaped and adapted to be rotated about a central axis of rotation. 
         [0013]    In preferred embodiments of the rotary chuck according to the present invention, the ring-shaped chuck body has an inner diameter that is greater than or equal to the predetermined diameter. 
         [0014]    In preferred embodiments of the rotary chuck according to the present invention, each of the gripping pins comprises a proximal part mounted within the chuck body and a distal part that projects outwardly from the chuck body, the distal part sliding horizontally through a respective opening in the chuck body toward the central axis of rotation during movement from the first position to the second position. 
         [0015]    In preferred embodiments of the rotary chuck according to the present invention, a drive ring is mounted coaxially within the chuck body for limited rotation relative thereto, the drive ring comprising a series of cam surfaces each of which engages a respective one of the series of gripping pins during relative rotation between the drive ring and the chuck body and moves the series of gripping pins from the second position to the first position. 
         [0016]    In preferred embodiments of the rotary chuck according to the present invention, each of the series of cam surfaces is comprised by a corresponding slot formed in the drive ring, each the slot extending obliquely to the central axis of rotation, and wherein a proximal part of each of the series of gripping pins is disposed within a corresponding one of the slots. 
         [0017]    In preferred embodiments of the rotary chuck according to the present invention, the drive ring comprises at least one permanent magnet affixed thereto, to permit the drive ring to be held stationary in relation to rotation of the chuck body, thereby to move the series of gripping pins from the second position to the first position. 
         [0018]    In preferred embodiments of the rotary chuck according to the present invention, the rotary chuck is configured to hold a wafer-shaped article of a predetermined diameter D2, and wherein the chuck body defines a central opening having a diameter D1, wherein D1≧D2−10 mm, whereby an overlap between a peripheral region of a wafer-shaped article of diameter D2 and the rotary chuck is at most 5 mm. 
         [0019]    In preferred embodiments of the rotary chuck according to the present invention, the chuck body is a magnetic ring rotor adapted to be drive in rotation without contact by a surrounding magnetic stator. 
         [0020]    In another aspect, the present invention relates to a device for processing wafer-shaped articles, comprising a process chamber and a rotary chuck disposed within the process chamber, the rotary chuck comprising a chuck body having a series of gripping pins that are movable by sliding horizontally and in unison relative to the chuck body from a first position in which the gripping pins are relatively more retracted into the chuck body to a second position in which the gripping pins are relatively more extended from the chuck body and in which the gripping pins are positioned so as to support a wafer-shaped article of a predetermined diameter. 
         [0021]    In preferred embodiments of the device according to the present invention, each of the gripping pins comprises a proximal part mounted within the chuck body and a distal part that projects outwardly from the chuck body, the distal part sliding through a respective opening in the chuck body during movement between the first and second positions. 
         [0022]    In preferred embodiments of the device according to the present invention, the distal parts slide horizontally through the respective openings toward a center of the chuck body during movement from the first position to the second position. 
         [0023]    In preferred embodiments of the device according to the present invention, each of the distal parts comprises a respective distal end configured to contact and support a peripheral edge of a wafer-shaped article when held by the rotary chuck, and wherein the distal ends face one another in the first and second positions of the series of gripping pins. 
         [0024]    In preferred embodiments of the device according to the present invention, the chuck body is ring-shaped and adapted to be rotated about a central axis of rotation, and further comprising a drive ring mounted coaxially within the chuck body for limited rotation relative thereto, the drive ring comprising a series of cam surfaces each of which engages a respective one of the series of gripping pins during relative rotation between the drive ring and the chuck body and moves the series of gripping pins from the second position to the first position. 
         [0025]    In preferred embodiments of the device according to the present invention, each of the series of cam surfaces is comprised by a corresponding slot formed in the drive ring, each the slot extending obliquely to the central axis of rotation, and wherein a proximal part of each of the series of gripping pins is disposed within a corresponding one of the slots. 
         [0026]    In preferred embodiments of the device according to the present invention, the drive ring comprises at least one permanent magnet affixed thereto, to permit the drive ring to be held stationary in relation to rotation of the chuck body, thereby to move the series of gripping pins from the second position to the first position 
         [0027]    In preferred embodiments of the device according to the present invention, the rotary chuck is configured to hold a wafer-shaped article of a predetermined diameter D2, and wherein the chuck body defines a central opening having a diameter D1, wherein D1≧D2−10 mm, whereby an overlap between a peripheral region of a wafer-shaped article of diameter D2 and the rotary chuck is at most 5 mm. 
         [0028]    In preferred embodiments of the device according to the present invention, the chuck body is a magnetic ring rotor, and wherein the process chamber comprises a magnetic stator mounted to an exterior surface of the process chamber and surrounding the magnetic ring rotor with a cylindrical wall of the process chamber being disposed between the magnetic stator and the magnetic ring rotor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which: 
           [0030]      FIG. 1 a    is a perspective view in section of a rotary chuck and device for processing wafer-shaped articles according to a preferred embodiment of the present invention; 
           [0031]      FIG. 1 b    is an enlarged view of the detail Ib in  FIG. 1   a;    
           [0032]      FIG. 1 c    is a fragmentary sectional view showing a preferred drive configuration of the chuck of  FIG. 1   a;    
           [0033]      FIG. 2 a    is a partial plan view along the line IIa-IIa of  FIG. 2   b;    
           [0034]      FIG. 2 b    is a fragmentary sectional view showing a preferred configuration for the gripping pin mechanism of the chuck of  FIG. 1   a;  and 
           [0035]      FIG. 2 c    is a view similar to that of  FIG. 2 b   , showing the pins in their first or retracted position, in which a wafer W may be unloaded from or loaded onto the rotary chuck. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0036]    The device  200  of  FIG. 1 a    comprises a chamber, an annular chuck  220  for gripping and rotating a wafer (disc-like article) and a stator  280  ( FIG. 1 b   ) disposed within a stator housing  290 . 
         [0037]    The chamber comprises a cylindrical wall  260 , a bottom plate  265  and a top plate (not shown). An upper dispensing tube  263  is led through the top plate and a lower dispensing tube  267  through the bottom plate  265 . 
         [0038]    The stator  280  is mounted to a stator base plate  205  concentric to the cylindrical wall  260 . The stator base plate  205  can be moved in axial direction with respect to the cylinder axis of the cylindrical wall  260 , e.g. with pneumatic jacks (not shown). The stator base plate  205  and the stator  280  mounted thereto have central openings, whose diameter is greater than the outer diameter of the cylindrical wall  260 . The top plate can also be moved in axial direction in order to open the chamber. In closed position the top plate is sealed against the cylindrical wall. 
         [0039]    The stator  280  comprises several coils for axial and radial bearing and for driving the rotor  285 , which is part of the annular chuck. Such arrangement is called active bearing and is further described in U.S. Pat. No. 6,485,531. 
         [0040]    The diameter of the annular chuck  220  is smaller than the inner diameter of the cylindrical wall so that it can freely levitate and rotate within the cylindrical wall  260 . The annular chuck  220  comprises an inner chuck base body  221  with an annular groove circumferentially surrounding the outside of the inner chuck base body  221 , the annular groove serving as the bearing for the drive ring  230 . 
         [0041]    The drive ring  230  is embodied as a cam ring  230  with obliquely-oriented slots  232 . The slots  232  receive the upwardly projecting proximal end parts  227  of gripping pins  226  ( FIG. 2 a   ). 
         [0042]    This embodiment has six gripping pins  226 , each of which has a proximal end  227  that is received in a corresponding slot  232  of the drive ring  230 . For securely gripping the wafer W, each gripping pin  226  is equipped with a horizontal notch at its distal end  228  ( FIGS. 2 b  and 2 c   ). 
         [0043]    The drive ring  230  may be mounted into the annular groove of the chuck base body  221  by forming the chuck base body  221  in two halves that join at the sectional plane IIa-IIa of  FIG. 2 b   , positioning the gripping pins  226  and drive ring  230  into the lower half of the chuck base body  221 , and then securing together the two halves of the chuck base body  221 . Thus, the drive ring  230  may be formed in one piece, and may if desired be completely encapsulated by the assembled upper and lower halves of the chuck base body  221 . 
         [0044]    Alternatively, the drive ring  230  may be formed of two separate segments, which are fixed together when inserted into the annular groove. The chuck base  221  and the drive ring  230  are connected via a helical spring  240  so that the drive ring  230  urges the pins  226  toward positions that are relatively closer to the center of the annular chuck  220 . 
         [0045]    Two permanent magnets  233  are mounted to the drive ring  230 . A plurality of at least twenty-four rotor magnets  285 , which are permanent magnets, are evenly arranged around the chuck base body  221 . These rotor magnets  285  are part of the drive and bearing unit namely part of the rotor (elements of the active bearing), which is mounted to the chuck base body  221 . 
         [0046]    The plurality of rotor magnets  285  and the drive ring  230  carrying the permanent magnets  233  are encapsulated in a hollow annular space provided by the chuck base body  221 , outer lower chuck cover  222 , and the rotor magnet cover  229 . Such rotor magnet cover  229  can be a stainless steal jacket. The covers  222  and  229  are annular and concentric with the chuck base body  221 . 
         [0047]    Attached to the stator base plate  205  is the stator and active bearing unit  280  which is concentrically arranged with respect to the cylindrical wall  260 . The bearing unit  280  corresponds with the rotor magnets  285  therefore levitating, bearing and rotating the chuck  220 . 
         [0048]    Below the active bearing unit  280  there are two pneumatic cylinders  250  mounted to the stator base plate  205 . On the distal ends of the rods of the pneumatic cylinders  250  locking magnets  255  (permanent magnets) are arranged. The locking magnets correspond to the permanent magnets  233  of the drive ring  230 . The pneumatic cylinders  250  are arranged so that the locking magnets  255  can be radially moved with respect to the axis of the cylindrical wall  260 . 
         [0049]    When the pins  226  shall be opened e.g. to release a wafer the following procedure is conducted. The pneumatic cylinders  250  move the locking magnets  255  in close proximity to the chuck  220  and the chuck is turned so that the permanent magnets  233  and therewith the drive ring  230  is locked by the locking magnets. A robotic transfer arm is inserted into the chamber through a side opening thereof (not shown), and an end effector of the transfer arm is moved upwardly into a position wherein it grips the peripheral edge of the wafer W at regions between the distal ends  228  of gripping pins  226 . Next the chuck is turned while the drive ring stands still and thus the pins  226  open, as shown in  FIG. 2 c   , such that the wafer W is supported entirely by the end effector of the robotic transfer arm, which may then remove the wafer from the chamber. Alternatively the chuck base body  221  might stand still while the pneumatic cylinders  250  are moved so that the locking magnets  255  tangentially turn (along the circumference of the chuck), whereby the drive ring  230  is turned. 
         [0050]    In particular, as the chuck  220  is rotated relative to the drive ring  230 , the proximal ends  227  of gripping pins  226  are moved radially inwardly by the slots  232  formed in drive ring  230 , which in turn causes the distal ends  228  of the gripping pins  226  to slide horizontally into a relatively more retracted position within chuck base body  221 , as shown in  FIG. 2 c   . For easing the movement of the gripping pins  226  additional sleeves can be inserted in the chuck base body  221 . Such sleeves can be further equipped with bearings in order to prevent liquids and/or gases from leaking into the chuck base body. 
         [0051]    When a wafer W is positioned for loading into the chuck, the locking magnets are withdrawn, which allows spring(s)  240  to cause the drive ring  230  and the chuck base body  221  to rotate relative to one another in the opposite direction. Slots  232  thereby drive the proximal ends  227  of gripping pins  226  radially inwardly of the chuck base body, such that the distal ends  228  of the gripping pins  226  move radially inwardly of the chuck and assume the relatively more extended position shown in  FIG. 2 b   , in which pins  226  contact and support the peripheral edge of wafer W. 
         [0052]    The novel configuration of gripping pins  226  and the manner in which they are mounted in chuck base body  221 , represents an improvement over the configurations shown in U.S. Pat. No. 8,490,634. In particular, the horizontal orientation of the distal ends  228  of pins  226 , and the ability of drive ring  230  to move those distal ends between the relatively more retracted and relatively more extended positions shown in  FIGS. 2 b  and 2 c    by a horizontal sliding motion of those distal ends relative to the chuck base body  221 , allows the chuck to be designed so that more of the wafer W can be exposed during processing. 
         [0053]    In the chucks of U.S. Pat. No. 8,490,634, where the distal ends of the pins are oriented vertically or substantially vertically, the chuck base body necessarily overlaps the wafer W to a greater extent than is necessary for the novel chuck designs described herein. In particular, for the chucks described in U.S. Pat. No. 8,490,634, the chuck base body will often overlie an annular peripheral region of the wafer W whose width is approximately 10 mm, which, in the case of a wafer whose diameter is 300 mm, represents about 13% of the wafer area. 
         [0054]    By contrast, it will be appreciated that the novel gripping pin and drive configuration described herein does not require such an overlap between a wafer and the chuck base body. Chucks for processing semiconductor wafers are designed to hold wafers of a predetermined diameter. If that diameter is taken as D2, then the central opening of the chuck base body of the preferred embodiments of the present invention may be taken as D1, and the chuck may be sized so that D1≧D2−10 mm, which is to say that the overlap between the peripheral region of a wafer of diameter D2 and the rotary chuck preferably is at most 5 mm. However, a lesser extent of overlap may be selected, for example, 2 mm, or there can be no overlap at all, by appropriate selection of the diameter D1 in relation to D2, and the lengths of the distal ends of the gripping pins. 
         [0055]    It will be understood that the foregoing description and specific embodiments shown herein are merely illustrative of the invention and the principles thereof, and that modifications and additions may be easily made by those skilled in the art without departing from the spirit and scope of the invention, which is therefore understood to be limited only by the scope of the appended claims.