Patent Publication Number: US-6666948-B2

Title: Silicon wafer polisher

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part application of U.S. patent application Ser. No. 09/840,506 filed on Apr. 23, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to devices for polishing workpieces and, more specifically, to a device for polishing silicon wafers including a planar template having a plurality of cavities wherein a silicon wafer is placed within a respective cavity for polishing to a thickness equivalent to the depth of the template cavity. 
     2. Description of the Prior Art 
     The prior art discloses numerous templates for lapping and polishing wafers to a desirable thickness determined by the depth of the template cavity. However, the prior art devices and methods each contain one or more undesirable characteristics that render them unsuitable for repeated use. 
     A prior art process of lapping and polishing blank wafers includes placing the workpieces into a template and placing the template upside down between a rotating pneumatic head and a table. A controlled flow of abrasive slurry flows onto the table surface during rotation of the pneumatic head whereby the wafer blanks are honed and polished to the thickness of the template. 
     There are two undesirable side effects that can occur with this method. As the wafers approach the thickness of the template cavity, the amount of fluid between the template and table decreases causing spotted changes in the surface temperature of the template and thereby burnishing the template. In addition, the cross sectional thickness of the finished wafer is affected. The wafers rotate within the cavity causing the wafers to continuously butt up against the wall of the cavity and rise from the cavity base. This potentially causes the edge thickness of the wafer to vary from the center thickness, especially in applications where tolerances are measured in the +/− tens of picometers. 
     It is thus desirable to provide a method and apparatus for polishing a wafer which overcomes both of the above discussed shortcomings with the prior art. It is further desirable to provide a method and apparatus for polishing a wafer which is able to increase the efficiency of present methods by reducing the number of templates used. It is even further desirable to provide a method and apparatus for polishing a wafer which is able to account for the varied thickness&#39; required within the end product. 
     Therefore because of the aforementioned problem it is felt that a need exists for the present invention and while the prior art may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention relates generally to devices for polishing workpieces and, more specifically, to a device for polishing silicon wafers including a planar template having a plurality of cavities wherein a silicon wafer is placed for polishing to a thickness equivalent to the depth of the template cavity. 
     A primary object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers that will overcome the shortcomings of prior art devices. 
     Another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers that can be used repeatedly. 
     Yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the apparatus includes templates substantially comprised of fiberglass-epoxy laminates. 
     Still yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the templates have a backing material adhesively affixed thereto. 
     Another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the templates include a backing adhesively affixed thereto formed from mylar or other suitable frictionless material. 
     Still yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers having a plurality of shims preferably manufactured from a suitable material such as polyurethane. 
     Yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the shim is affixed to the base of the plurality of cavities within said template thereby adjusting the depth of the cavity. 
     Still yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the affixed shim is of smaller diameter than the diameter of the plurality of workpiece cavities within the template and the periphery of the wafer contained within the workpiece cavity extends beyond the circumference of the shim. 
     Yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers able to reduce tapering of the wafer. 
     Another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the plurality of shims are of various thickness&#39; that can be removably inserted into each of the plurality of cavities within the template. 
     Yet another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers wherein the template can be used to produce wafers of various and/or calculated thickness&#39;. 
     Additional objects of the present invention will appear as the description proceeds. 
     A method and apparatus for forming wafers of varying thickness&#39; is disclosed by the present invention. The apparatus includes a template. The template is formed of a main disk including a plurality of cavities extending into a first side thereof and a backing plate positioned on a side of the main disk opposite the first side. Holding disks are moistened and positioned within respective cavities for releasably securing a wafer in the cavity. When the template is releasably secured to and rotatable with a rotating head and positioned such that the first side faces a lapping and polishing surface, wafers received by the cavities are lapped and polished upon rotation of the rotating head. A plurality of shims are selectively received within respective cavities between a base of the cavity and the holding disk for adjusting a depth of the cavity thereby adjusting an amount of a wafer to be lapped and polished. The shims have varying thickness&#39; and are color coated, each color being representative of a predetermined thickness for the shim. A mylar layer is bonded to a side of the backing plate opposite the main disk. A liquid is provided atop the lapping and polishing surface upon rotation of the templates. 
     The present invention overcomes the shortcomings of the prior art by providing a method and device whereby employing the reusable workpiece template and selectively inserting shims of various thickness&#39; produce semiconductor wafers of varying thickness&#39;. 
     In addition, the workpiece template having a shim centrally affixed and positioned within the base of the workpiece cavities reduce tapering of the wafer. Furthermore, having a suitable frictionless material, such as mylar, induce rotation of the wafer thereby reducing tapering. 
     The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawing, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawing, like reference characters designate the same or similar parts throughout the several views. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     In order that the invention may be more fully understood, it will now be described, by way of example, with reference to the accompanying drawing in which: 
     FIG. 1 is a perspective view of the silicon wafer polishing holder of the present invention; 
     FIG. 2 is a bottom side view of a workpiece template used with the silicon wafer polishing holder of the present invention; 
     FIG. 3 is a perspective view of the workpiece template of the silicon wafer polishing holder of the present invention; 
     FIG. 4 is a cross sectional view of the workpiece template of the silicon wafer polishing holder of the present invention; 
     FIG. 5 is an exploded view of the workpiece template of the silicon wafer polishing holder of the present invention; 
     FIG. 6 is a top exploded view of a holding disk of the silicon wafer polishing holder of the present invention; 
     FIG. 7 is a perspective view of a plurality of color-coded shims for use with the silicon wafer polishing holder of the present invention; 
     FIG. 8 is an exploded perspective view of the workpiece cavity of the silicon wafer polishing holder of the present invention; 
     FIG. 9 is an exploded perspective view of a workpiece cavity of the silicon wafer polishing holder of the present invention including a shim positioned therein for adjusting the depth of the cavity; 
     FIG. 10 is an exploded view of the workpiece cavity of the silicon wafer polishing holder of the present invention including a plurality of shims positioned therein for adjusting the depth of the cavity; 
     FIG. 11 is a bottom side view of the workpiece template the silicon wafer polishing holder of the present invention showing workpiece cavities in exploded form; 
     FIG. 12 is a cross-sectional view of a workpiece cavity of the silicon wafer polishing holder of the present invention; 
     FIG. 13 is a cross-section side view of the silicon wafer polishing holder of the present invention including more than one shim within the cavity; 
     FIG. 14 is a bottom side view of the workpiece template of the silicon wafer polishing holder of the present invention; 
     FIG. 15 is a bottom side view of an alternate workpiece template embodiment for use with the silicon wafer polishing holder of the present invention; and 
     FIG. 16 is a perspective view of an alternate embodiment of the silicon wafer polishing holder of the present invention; 
     FIG. 17 is a cross sectional view of an alternate workpiece template for use in the silicon wafer polishing holder of the present invention; 
     FIG. 18 is an exploded view of the alternate workpiece template for use in the silicon wafer polishing holder of the present invention; 
     FIG. 19 is a top side view of the holding disk for use in the silicon wafer polishing holder of the present invention; 
     FIG. 20 is a back side view of the holding disk for use in the silicon wafer polishing holder of the present invention; 
     FIG. 21 is a cross sectional view of the holding disk for use in the silicon wafer polishing holder of the present invention; 
     FIG. 22 is cross sectional view of the holding disk and a shim with an adhesive layer positioned therebetween for use in the silicon wafer polishing holder of the present invention; 
     FIG. 23 is cross sectional view of the holding disk positioned atop a shim for use in the silicon wafer polishing holder of the present invention; 
     FIG. 24 is a cross sectional view of one shim positioned atop a second shim with an adhesive layer positioned therebetween for use in the silicon wafer polishing holder of the present invention; and 
     FIG. 25 is a top side view of an alternative main plate for use in the silicon wafer polishing holder of the present invention. 
    
    
     DESCRIPTION OF THE REFERENCED NUMERALS 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the Figures illustrate the silicon wafer polishing holder of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures. 
       10  silicon wafer polishing holder of the present invention 
       12  rotating pneumatic heads 
       14  lapping and polishing surface 
       16  workpiece template 
       18  tube 
       20  supply of moistening liquid 
       22  top side of lapping and polishing surface 
       24  arrows indicating rotation of the rotating pneumatic head 
       26  cavity within workpiece template 
       28  bottom surface of workpiece template 
       30  shim 
       32  top side of the workpiece template 
       34  backing plate 
       36  main plate 
       38  base of cavity 
       40  mylar layer 
       42  adhesive layer 
       44  aperture in main disk 
       46  adhesive layer 
       47  top side of holding disk 
       48  holding disk 
       49  bottom side of holding disk 
       50  wafer 
       51  grooves 
       52  portion of wafer remaining after lapping and polishing 
       54  portion of wafer removed by lapping and polishing 
       56  plurality of grooves extending along the top surface of main plate 
       58  center of workpiece template 
       60 . Alternate workpiece template 
       62 . Alternate main plate 
       63 . Top Side of main plate 
       64 . Adhesive layer 
       66 . Recessed cavity 
       68 . Base of the recessed cavity 
       70 . Adhesive layer 
       72 . Adhesive layer 
       73 . Recessed cavity 
       74 . Second alternate main plate 
       76 . Grooves 
       78 . Top side of second alternate main plate 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, FIGS. 1 through 25 illustrate the silicon wafer polishing holder of the present invention indicated generally by the numeral  10 . 
     The silicon wafer polishing holder  10  of the present invention is shown polishing a wafer in FIG.  1 . As can be seen from this view, the silicon wafer polishing holder  10  includes a plurality of rotating pneumatic heads  12 . The plurality of rotating pneumatic heads  12  are positioned above a lapping and polishing surface  14 . A workpiece template  16  is positioned between the lapping and polishing surface  14  and a respective one of each of the plurality of rotating pneumatic heads  12 . The rotating heads rotate as indicated by the arrows labeled with the numeral  24 . Each workpiece template  16  includes a main plate  36  having a plurality of cavities extending therein. The cavities extend at least partially through the main plate and possible entirely through the main plate  36 . Each cavity is able to receive a silicon wafer, not shown in this figure. Each workpiece template  16  is positioned under and rotated by the respective rotating pneumatic head  12 . The workpiece templates  16  place the silicon wafers in communication with the lapping and polishing surface  14  and rotate the silicon wafers generating a frictional force between the silicon wafers and the lapping and polishing surface  14 . The frictional force acts to polish the silicon wafers. A tube  18  is positioned above the lapping and polishing surface  14  for providing a supply of moistening liquid  20  to a top side  22  of the lapping and polishing surface and between the lapping and polishing surface  14  and the workpiece template  16 . The supply of the moistening liquid  20  reduces the heat produced by the friction between the wafer and the lapping and polishing surface  14  while also aiding in producing a suction force to maintain the position of the wafer within the cavity. 
     A bottom side view of the workpiece template  14  of the silicon wafer polishing holder  10  of the present invention is shown in FIG.  2 . From this view, the workpiece template  14  is shown having a main plate  36  including the plurality of cavities  26  extending into a bottom surface  28  thereof. Positioned within each cavity  26  is a shim  30  having a diameter smaller than the diameter of the workpiece cavity  26 . Each shim  30  has a predetermined thickness and insertion of a shim  30  within a cavity  26  adjusts the depth of the cavity  26  in which it is positioned. The adjustment of the depth of the cavity  26  allows a user to determine the amount of lapping and polishing to be performed on a wafer positioned within the cavity  26 . 
     A perspective bottom side view of the workpiece template  14  is illustrated in FIG.  3 . This figure shows the bottom side  28  of the planar main plate  36  including the plurality of cavities  26  extending therein. Positioned on a top side  32  of the main plate  36  opposite the bottom side  28  is a backing plate  34 . The main plate  36  is preferably formed of fiberglass-epoxy laminates. 
     A cross sectional view of the workpiece template  14  is shown in FIG.  4 . This figure shows the main plate  36  formed from heat and moisture resistant material such as fiberglass-epoxy laminates. Extending into the bottom side  28  of the main plate  36  and possibly extending through the main plate  36  are the plurality of cavities  26 . The cavities  26  extend at least partially and possibly fully through the main plate  36 . The backing plate  34  is adhesively bonded to the top side  32  of the main plate  36 . The backing plate acts as a base  38  for the cavities  26  should the cavity  26  extend entirely through the main plate  36 . On a side of the backing plate  34  opposite the main plate  36  is a mylar layer  40 . The mylar layer  40  is adhesively bonded to the backing plate by an adhesive layer  42 . 
     An exploded view of the workpiece template  14  is illustrated in FIG.  5 . As can be seen from this view, the workpiece template  14  includes the main plate  36  having a plurality of apertures  44  extending therethrough. When the backing plate  34  is secured to the top side  32  of the main plate  36 , the apertures  44  each form a respective one of the cavities  26  having a depth defined by the base  38 . The backing plate  36  is bonded to the main plate  36  by an adhesive layer  46 . Bonded to the backing plate  34  on a side opposite the main plate  36  is a mylar layer  40 . A second adhesive layer  40  secures the mylar layer  40  to the backing plate  34 . A shim  30  having a desired thickness may be adhesively bonded within the apertures  44  of the main plate  36  to adjust the depth of the cavity  26 . The shim  30  may be of any desired thickness to adjust the depth of the cavity  26  in which it is positioned. The shims  30  can be of varying thickness&#39; therefore, a shim  30  in one cavity  26  need not be of the same thickness as a shim  30  in any other cavity  26 . 
     Within each cavity  26  a holding disk  48  is positioned atop the shim  30 . A top side view of a holding disk  48  is shown in FIG.  6 . The holding disk  48  is formed from a felt material and acts to hold a wafer within the workpiece template cavity  26 . Positioned within the cavity between the holding disk  48  and the base of the cavity  38  is a shim  30  for adjusting the depth of the cavity  26 . The shim  30  may be adhesively fixed to the backside of the holding disk  48 . Prior to insertion of the wafer the felt material of the holding disk  48  is moistened with a liquid. The liquid is partially forced out when the wafer is placed in the cavity  26  forming a suction bond between the wafer and workpiece template  14 . 
     A plurality of shim disks  30  are illustrated in FIG.  7 . The shim disks  30  are color-coded. Each color is associated with a particular thickness for the shim  30 . For each color shim disk  30  a face side view and perspective view is shown in this figure. The perspective view illustrates an exemplary thickness for each color shim disk  30 . The differing colors are used to identify a specific thickness for each shim disk  30  and thus be able to accurately adjust the depth of each cavity  26 . 
     FIGS. 8,  9  and  10  each illustrate an exploded perspective view of the elements within a workpiece cavity  26 . FIG. 8 illustrates a cavity  26  without a shim disk  30  therein. FIG. 9 illustrates a cavity  26  with a single shim disk  30  therein. FIG. 10 illustrates a cavity  26  with three shim disks  30  therein. As can be seen from these figures, the main disk  36  is positioned atop the backing plate  34  with the adhesive layer  46  positioned therebetween. Positioned within the cavity  26  and atop the base  38  is positioned the holding disk  48 . If use of shim disks  30 , as is shown in FIGS. 9 and 10, is desired to adjust the depth of the cavity  26 , the shim disks  30  are positioned between the base  38  and the holding disk  48 . A wafer  50  to be lapped and polished is positioned atop the holding disk  48 . The holding disk  48  is moistened and the wafer  50  is placed atop the holding disk  48 . Moistening of the holding disk  48  creates a suctional force within the cavity  26 . Placement of the wafer  50  atop the moistened holding disk  48  utilizes the suction to maintain the wafer  50  in a stationary position within the cavity  26 . The placement of a shim disk  30  within the cavity as shown in FIG. 9 decreases the depth of the cavity  26  thereby raising the height of the wafer within the workpiece cavity  26 . This creates a cavity having a smaller depth and thus, upon lapping and polishing produces a thinner wafer  50 . The placement of additional shim disks  30  within the cavity  26  as shown in FIG. 10 decreases the depth of the cavity  26  more so than as shown in FIG.  9 . This raises the height of the wafer within the workpiece cavity  26  to a greater extent thereby creating a cavity  26  having an even smaller depth. Upon lapping and polishing a wafer  50  within a cavity  26  having a depth as shown in FIG. 10, an even thinner wafer  50  is produced. Using variable amounts of shim disks  30  of differing thickness&#39; allows the creation of a cavity having a desired depth. 
     FIG. 11 illustrates an exploded view of the cavities  26  of an entire template  14 . Each of the cavities  26  has a plurality of shim disks  30  positioned therein to adjust the thickness of the cavity  26 . It is thus shown that by positioning differing amounts of shim disks  30  having varying thickness&#39; within each cavity  26 , a number of wafers  50  are able to be produced at a single time using a single template  14  whereby each wafers  50  produced can be varied to be a desired thickness. This allows for numerous wafers  50  of varying thickness&#39; to be produced at a single time. 
     A cross-sectional view of a workpiece cavity  26  is shown in FIGS. 12 and 13. These figures illustrate the template  14  and elements positioned therein prior to lapping and polishing. Positioned within the cavity  26  and above the base  38  are shims  30 . Positioned above the shims  30  is the holding disk  48 . The wafer  50  is then positioned and held above the holding disk  48  by the suctional force created when the holding disk  48  is moistened. As can be seen from these figures, prior to lapping and polishing, the wafer  50  extends above the top of the cavity  26 . The wafer  50  is thus divided into two portions, a portion remaining after lapping and polishing  52  and a portion removed by lapping and polishing  54 . Thus, when the template  14  is secured to the rotating pneumatic head  12  and against the lapping and polishing surface  16 , the portion  54  extending above the top of the cavity  26  will be removed. The thickness of the portion being removed  54  is dependent upon the number of shims  30  positioned within the cavity  26  and the thickness of the shims  30 . In order to calculate the thickness of the wafer  50  to be remaining after lapping and polishing, “X” represents the workpiece cavity depth. While “A”, “B” and “C” represent the components placed within the cavity. “A” being the shims, “B” being the holding disk and “C” being the wafer  50 . “D” or  54  represents the material that will be removed from the wafer  50  by lapping and polishing. This results in a finished lapped and polished wafer  52  having a thickness of “E”. 
     The main plate  36  is illustrated in FIG.  14 . As can be seen from this figure, the main plate  36  includes a plurality of grooves  56  extending along the top surface  28  thereof. The plurality of grooves  56  draw liquid toward a center  58  of the workpiece template  14  while in operation. The drawing of the liquid towards the center of the workpiece template  14  aids in retaining the wafers within their respective cavities  26  during lapping and polishing. 
     A workpiece template including an increased number of workpiece cavities  26  is illustrated in FIG.  15 . The template  14  illustrated herein also includes an increased surface area. Increasing the number of cavities  26  enables the lapping and polishing of a greater number of wafers  50  at a single time thereby increasing production limits. 
     A perspective view of the workpiece template  14  shown in FIG. 15 is illustrated in FIG.  16 . This workpiece template  14  includes an increased number of workpiece cavities  26  and increased surface area. This backing plate secured to the main disk  36  is of an increased size to match the dimensions of the workpiece template  14  for use with larger polishing machines. 
     A cross sectional view of an alternate embodiment for the workpiece template  60  is shown in FIG.  17 . The alternate workpiece template  60  includes an alternate main plate  62 . The alternate main plate  62  is preferably formed from heat and moisture resistant material such as fiberglass-epoxy laminates. However, any material able to perform the functions necessitated by the alternate main plate  62  may be used. The alternate main plate  62  includes a top side  63  having at least one recessed cavity  66  extending at least partially therethrough. An adhesive layer  64  having a circumference substantially equal to the circumference of the recessed cavity  66  is positioned within each recessed cavity  66 . In order to adjust the depth of the recessed cavity  66 , a shim  30  can be added thereto. The shim  30  is placed on top of the adhesive layer  64  and secured within the recessed cavity  66 . The adhesive layer is described for purposes of example. However, any method of releasably securing the shim  30  to the base of the recessed cavity  68  may also be used. The alternate main plate  62  is bonded to a mylar layer  40  by the adhesive layer  42 . The mylar layer  40  is bonded to a side of the main plate  62  opposite the top side. 
     An exploded view of the alternate workpiece template  60  is illustrated in FIG.  18 . The alternate workpiece template  60  consists of the alternate main plate  62  having at least one and preferably a plurality of recessed cavities  66 . The depth of each recessed cavity  66  is determined during construction of the alternate main plate  62 . The cavities  66  are provided to extend at least partially through the main plate  62 . The mylar layer  40  is bonded to a side of the alternate main plate  62  opposite the top side  63 . The aforementioned mylar layer  40  is preferably bonded to the main plate  62  by adhesive layer  42 . An adhesive layer  64  is placed within the recessed cavity  66 . The adhesive layer  64  preferably has a circumference substantially equivalent to the circumference of the recessed cavity  66 . A shim  30  having a desired thickness is selectively secured within the recessed cavity  66  by the adhesive layer  64 . Placement of the shim  30  within the cavity  66  allows for adjustment of the depth of the recessed cavity  66  to a desired level. Alternatively the shim  30  may be releasably held in place by any material able to be placed within the cavity  66  that functions to hold the shim  30  in place. To further alter the depth of recessed cavity  66 , a second shim  30  can be placed directly on top of the shim  30  adhesively bonded to the base of the recessed cavity  68 . If multiple shims  30  are used to alter the depth of the recessed cavity, the shims  30  may be held together by additional adhesive layers  64  positioned therebetween. However, the shims  30  can also be stacked on top of the shim  30  bonded to the base of the recessed cavity  68 . The shim  30  or combination of shims  30  can be of varying thickness. As previously discussed the shims  30  may be color coated, each color identifying a respective shim thickness. Therefore, a shim  30  or combination thereof may produce recessed cavities  66  having differing depths within a single main plate  62 . 
     Positioned within the recessed cavity  66  atop the base of the cavity  68  is the holding disk  48 . The holding disk  48  is moistened and a wafer  50  is placed atop the moistened holding disk  48 . Placement of the wafer  50  atop the moistened holding disk  48  utilizes a suctional force to maintain the wafer  50  in a stationary position within the recessed cavity  66 . If use of shim disks  30 , as shown in FIGS. 16 and 17, is desired to adjust the depth of the cavity  66 , the shim disks are positioned between the base of the cavity  68  and the holding disk  48 . The placement of a shim disk as shown in FIGS. 16 and 17 decreases the depth and thus, upon lapping and polishing produces a thinner wafer  50 . Using variable amounts of shim disks  30  of differing thickness allows the creation of a cavity  66  having a desired depth. 
     The holding disk  48  is illustrated in FIGS. 19 and 20 with FIG. 19 showing a view of the top side thereof and FIG. 20 showing a view of the bottom side thereof. The bottom side  49  of the holding disk  48  includes grooves  51 . The grooves  51  are preferably cut into the bottom side  49  of the holding disk  48  in a graph-like pattern. The grooves  51  are provided for increasing the suctional force created between the holding disk  48  and shims  30  positioned therebelow after the holding disk  48  is moistened and inserted into the cavity. Although the grooves are shown in the form of a graph like pattern, grooves having any desired pattern may be cut into the bottom side as long as the grooves are able to increase the suctional force created with the shims  30  positioned therebelow. The grooves  51  cut in the bottom side  49  of the holding disk  48  are better illustrated by the cross sectional view of the holding disk  48  in FIG.  21 . FIG. 21 shows alternating indentations in the bottom side  49  of the holding disk  48  representative of the grooves  51 . 
     FIGS. 22 and 23 show the different methods by which the holding disk  48  can be releasably secured to a shim  30 . FIG. 22 shows the holding disk  48  positioned atop the shim  30 . Positioned between the bottom side  49  of the holding disk  48  and the top side of the shim  30  is an adhesive layer  70 . When applied, the adhesive layer  70  fills the spaces created by any grooves  51  cut into the bottom side  49  of the holding disk  48  to thereby increase the force holding the holding disk  48  and the shim positioned therebelow together. Should the holding disk  48  not have grooves cut therein, the adhesive layer  70  provides the sole force securing the holding disk  48  and shim  30  positioned therebelow together. FIG.  23  shows an alternative method by which the holding disk  48  can be releasably secured to the shim  30 . FIG. 23 shows the holding disk  48  positioned atop the shim  30 . In this embodiment, there is no adhesive layer, rather, upon being moistened the holding disk  48  uses the grooves  51  cut in the bottom side  49  to create an increased suctional force. The increased suction force acts to releasably secure the holding disk  48  to the shim  30 . 
     FIG. 24 illustrates a cross sectional view of two shims  30 . The shims  30  function to alter the depth of the recessed cavity  68  thereby altering the thickness of the wafer  50  being polished. Using multiple shims  30  allows for greater variance in the depths of the recessed cavity  68 . FIG. 24 shows a first shim  30  positioned atop a second shim  30 . These shims  30  are releasably secured together via an adhesive layer  72  positioned therebetween. Upon being secured together the newly created thicker shim  30  is ready to be received by the cavity  68 . 
     FIG. 25 is a top side view of a second alternate main plate  74 . The main plate  74  is preferably formed from heat and moisture resistant material such as fiberglass-epoxy laminates. However, any material able to perform the functions necessitated by the main plate  74  may be used. The main plate  74  includes a top side  78  having at least one recessed cavity  73  extending at least partially therethrough. The base  75  of each at least one recessed cavity  73  having grooves  76  carved therein. The grooves  76  function to increase the suctional force created between the base of the recessed cavity  75  and a shim  30  or the holding disk  48  positioned within the cavity  75 . The grooves  76  present an alternative means for releasably securing the shim  30  or the holding disk  48  to the base of the cavity  75 . 
     The operation of the workpiece template and apparatus for lapping and polishing silicon wafers  10  will now be described with reference to the figures. In operation, the workpiece template and apparatus for lapping and polishing silicon wafers  10  is prepared for use. In preparing the workpiece template and apparatus for lapping and polishing silicon wafers  10 , a backing piece  34  is secured to the bottom side  28  of the main disk  36  by an adhesive layer  46 . The backing piece  34  forms a base  38  for the cavities  26 . On a side of the backing piece  34  opposite the main disk  36 , a mylar layer  40  is secured by a second adhesive layer  42 . Alternatively a first main plate  62  that contains recessed cavities  66  can be utilized to lap and polish wafers  50 , as well as a second main plate  74  that contains recessed cavities  75 . A mylar layer  40  is bonded to a side opposite the top side of the main plate  62  preferably by means of an adhesive layer  42 . Each cavity  26 , 66 , 73  is now prepared by placing a desired number of shims  30  of varying thickness therein. The number and thickness of the shims  30  placed within each cavity  26 , 66 , 73  determines the depth of the cavity  26  and the height to which the wafer  50 , when placed within the cavity  26 , 66 , 73  will extend thereabove. After placing the shims  30  in each cavity  26 , 66 , 73  a holding disk  48  is moistened and positioned within each cavity  26 , 66 , 73  above the shims  30 . The template  14  is now prepared to receive wafers  50  within respective cavities  26 , 66 , 73 . The wafers  50  are positioned within a predetermined cavity  26 , 66 , 73  having a predetermined depth determined by the number and thickness of shims  30  positioned therein. A portion of the wafer  52  is seated within the cavity below the bottom side  28  thereof. A portion of the wafer  54  is positioned extending through the rim of the cavity  26 , 66 , 73  and above the bottom side  28 . 
     The wafers are now prepared to be lapped and polished. The template is now received by the rotating pneumatic head  12  of the apparatus for lapping and polishing silicon wafers  10 . When connected to the rotating pneumatic head  12 , the template  14  is positioned such that the bottom side  28  and the wafers  50  are directly above the lapping and polishing surface  16 . The portion of the wafer  54  is positioned extending through the rim of the cavity  26 , 66 , 73  and above the bottom side  28  is placed in contact with the lapping and polishing surface  16 . Upon turning on the portion of the wafer  54  is positioned extending through the rim of the cavity  26 , 66 , 73  and above the bottom side  28 , the rotating pneumatic heads  12  begin to rotate thereby rotating the template and the wafers  50  positioned within the cavities  26 , 66 , 73 . Rotation of the wafers  50  causes a frictional force to develop between the portion of the wafer  54  is positioned extending through the rim of the cavity  26 , 66 , 73  and above the bottom side  28  and the lapping and polishing surface  16 . The frictional force causes lapping and polishing of the wafer  50  to occur. The lapping and polishing of the wafer  50  continues until the portion of the wafer  54  is positioned extending through the rim of the cavity  26 , 66 , 73  and above the bottom side  28  is removed and the thickness of the wafer  50  equals the thickness of the portion of the wafer  54  is positioned within the cavity  26 , 66 , 73 . Throughout the rotation of the rotating pneumatic heads  12 , a liquid is deposited on top of the lapping and polishing surface thereby cooling the surface. As each wafer  50  within respective cavities  26 , 66 , 73  are polished to the same level, i.e. the level of the bottom surface of the main disk  36 , the production of all wafers is complete simultaneously. Furthermore, the thickness of each wafer  50  is dependent on the portion of the wafer which extends into the cavity  26 , 66 , 73 . Thus, wafers  50  of various sizes are able to be produced simultaneously. 
     From the above description it can be seen that the method and apparatus for lapping and polishing silicon wafers of the present invention is able to overcome the shortcomings of prior art devices by providing a method and apparatus for lapping and polishing silicon wafers which is able to be used repeatedly to produce a plurality of silicon wafers. The apparatus for lapping and polishing silicon wafers includes templates having a main disk substantially comprised of fiberglass-epoxy laminates and including cavities extending therein. A backing material adhesively affixed to the main disk and a layer formed of mylar or other suitable frictionless material is affixed to the backing material. A plurality of shims manufactured from a suitable material such as polyurethane may be affixed to the base of the cavities for adjusting the depth of the cavity. The shims are removably inserted into each of the plurality of cavities within the template. Another object of the present invention is to provide a method and apparatus for lapping and polishing silicon wafers having a plurality of shims of various thickness&#39; that can be removably inserted into each of the plurality of cavities within the template whereby the template can be used to produce wafers of various and/or calculated thickness&#39;. The method and apparatus for lapping and polishing silicon wafers is also able to reduce tapering of the wafer. Furthermore, the method and apparatus for lapping and polishing silicon wafers of the present invention is simple and easy to use and economical in cost to manufacture. 
     It will be understood the each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
     While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.