Abstract:
An apparatus for planarizing a workpiece has a web with a face which is positioned adjacent the workpiece during planarization. At least one tension assembly is configured to maintain tension of the web. An orbiting assembly is configured to orbit the web relative to the workpiece. The apparatus for planarizing a workpiece may include first and second polishing surfaces where the first polishing surface has a substantially horizontal web with a face which is positioned adjacent the workpiece during the planarization process. The apparatus may also have a rotatable carousel and at least two workpiece carriers suspended from the carousel. Each of the carriers is configured to carry a workpiece and press the workpiece against one of the polishing surfaces while causing relative motion between the workpiece and the polishing surface. An apparatus for planarizing a workpiece which includes a plurality of polishing stations is also disclosed. At least one of the polishing stations has a web with a first face which is positioned adjacent the workpiece during planarization . The apparatus also includes an orbiting assembly configured to orbit the web relative to the workpiece.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     This is a divisional application of and claims priority to U.S. Non-Provisional application Ser. No. 09/705,307, entitled “Orbiting Indexable Belt Polishing Station for Chemical Mechanical Polishing”, filed on Nov. 3, 2000, Now U.S. Pat. No. 6,793,565, which application is incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to systems for polishing or planarizing workpieces such as semiconductor wafers. More particularly, it relates to an improved apparatus and method for planarizing a wafer using an orbiting indexable fixed-abrasive web. 
     BACKGROUND OF INVENTION 
     Many electronic and computer-related products, such as semiconductors, CD-ROMs, and computer hard disks, require highly polished surfaces in order to achieve optimum operational characteristics. For example, high-quality and extremely precise wafer surfaces are often needed during the production of semiconductor-based integrated circuits. During the fabrication process, the wafers generally undergo multiple masking, etching, and dielectric and conductor deposition processes. Because of the high-precision required in the production of these integrated circuits, an extremely flat surface is generally needed on at least one side of the semiconductor wafer to ensure proper accuracy and performance of the microelectronic structures created on the wafer surface. As the size of integrated circuits decreases and the density of microstructures on integrated circuits increases, the need for accurate and precise wafer surface polishing increases. 
     Chemical Mechanical Polishing (“CMP”) machines have been developed to polish or planarize semiconductor wafer surfaces to the flat condition desired for integrated circuit components and the like. For examples of conventional CMP processes and machines, see U.S. Pat. No. 4,805,348, issued Feb. 21, 1989 to Arai et al; U.S. Pat. No. 4,811,522, issued Mar. 14, 1989 to Gill; U.S. Pat. No. 5,099,614, issued Mar. 31, 1992 to Arai et al; U.S. Pat. No. 5,329,732, issued Jul. 19, 1994 to Karlsrud et al; U.S. Pat. No. 5,498,196, issued Mar. 12, 1996 to Karlsrud et al; 
     U.S. Pat. No. 5,498,199, issued Mar. 12, 1996 to Karlsrud et al; U.S. Pat. No. 5,558,568, issued Sep. 24, 1996 to Talieh et al; and U.S. Pat. No. 5,584,751, issued Dec. 17, 1996 to Kobayashi et al. 
     Typically, a CMP machine includes a wafer carrier configured to hold, rotate, and transport a wafer during the process of polishing or planarizing the wafer. During a polishing operation, a pressure-applying element (e.g., a rigid plate, a bladder assembly, or the like), which may be integral to the wafer carrier, applies pressure such that the wafer engages the polishing surface with a desired amount of force. The carrier and the polishing pad are rotated, typically at different rotational velocities, to cause relative lateral motion between the polishing pad and the wafer and to promote uniform polishing. 
     Commercially available polishing pads may utilize various materials, as is known in the art. The hardness and density of the polishing pad depends on the material that is to be polished and the degree of precision required in the polishing process. Typically, conventional polishing pads may be formed from a blown polyurethane, such as the IC and GS series of polishing pads available from Rodel Products Corporation in Scottsdale, Ariz. 
     In conventional CMP apparatus, the platens use polishing pads the entire surface of which are used to planarize each wafer, with the result that the first wafer sees a totally fresh pad while the last wafer sees a pad in glazed condition. In addition, during polishing, the polishing pad wears unevenly, developing worn tracks that result in nonuniform polishing of the wafer. In order to minimize this problem, it is well known in the art to recondition the pad between each wafer, or a certain number of wafers, being processed. However, adding the pad-reconditioning step to the wafer planarization process typically slows the throughput of the apparatus. Also, while reconditioning the pad does assist in making a used pad appear more like a fresh pad, the pad nevertheless continues to deteriorate through its life introducing a variable that alters the planarization process from wafer to wafer. 
     Planarization of wafers using linear belts or indexable strips are known in the art. For examples of apparatus using such planarization devices, see U.S. Pat. No. 5,335,453, issued Aug. 9, 1994 to Baldy, et al., and International Application No. PCT/US98/06844, published Oct. 15, 1998. These apparatus typically include a belt which moves linearly relative to a wafer that is urged against the belt by a wafer carrier. The wafer carrier also causes rotary or oscillating movement of the wafer against the linear belt. 
     While prior art devices which use orbiting wafer carriers are known, such devices pose several disadvantages. The orbiting wafer carriers may generate vibrations which create noise that adversely effects endpoint detection devices, particularly acoustic endpoint detection devices. In addition, in multi-polishing station systems, the vibration generated by one wafer carrier may translate to other neighboring wafer carriers, thereby adversely affecting uniformity of the planarization performed by the neighboring wafer carriers. 
     A need therefore exists for an apparatus and method of planarizing wafers that enhances the planarization of the wafers. A need further exists for an apparatus and method of planarizing wafers that allows each wafer to experience similar pad conditions as all other wafers. 
     SUMMARY OF INVENTION 
     These and other aspects of the present invention will become more apparent to those skilled in the art from the following non-limiting detailed description of preferred embodiments of the invention taken with reference to the accompanying figures. 
     In accordance with an exemplary embodiment of the present invention, an apparatus for planarizing a workpiece includes a web with a face which is positioned adjacent the workpiece during planarization. At least one tension assembly is configured to maintain tension of the web. An orbiting assembly is configured to orbit the web relative to the workpiece. 
     In accordance with another exemplary embodiment of the present invention, an apparatus for planarizing a workpiece includes at least first and a second polishing surfaces wherein the first polishing surface has a substantially horizontal web with a face. The face is positioned adjacent the workpiece during the planarization process. The apparatus has a rotatable carousel and at least two workpiece carriers suspended from the carousel. The carriers are configured to carry a workpiece and press the workpiece against one of the polishing surfaces while causing relative motion between the workpiece and the polishing surface. 
     In accordance with yet another embodiment of the present invention, a compressible polishing pad is removably mounted to the second polishing surface. 
     In accordance with a further embodiment of the present invention, the apparatus has a third polishing surface having a low-compressibility polishing pad removably mounted thereto. 
     In accordance with yet another embodiment of the present invention, a method of planarizing a workpiece includes the steps of: loading a first workpiece on one of a plurality of workpiece carriers supported by a rotatable carousel; pressing the first workpiece against a horizontal web and causing relative motion between the first workpiece and the web so as to planarize the first workpiece; rotating the carousel to position the first workpiece adjacent a compressible polishing surface; and pressing the first workpiece against the compressible polishing surface and causing relative motion between the first workpiece and the compressible polishing surface so as to remove microscratches from the first workpiece. 
     In accordance with yet a further embodiment of the present invention, an apparatus for planarizing a workpiece includes a plurality of polishing stations wherein at least one of said plurality of polishing stations comprises a web with a first face which is positioned adjacent the workpiece during panarization. An orbiting assembly is configured to orbit the web relative to the workpiece. 
     These and other aspects of the present invention are described in the following description, claims and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Exemplary embodiments of the present invention will hereafter be described in conjunction with the appended drawing figures, wherein like designations denote like elements, and: 
         FIG. 1  is a side view illustration showing an orbiting indexable web polishing station according to an embodiment of the present invention. 
         FIG. 2  is a side view illustration showing an orbiting indexable web polishing station according to another embodiment of the present invention. 
         FIG. 3  is a perspective view illustration of a distribution manifold of an indexable web polishing station according to another embodiment of the present invention. 
         FIG. 4  is an oblique view illustration showing a carousel CMP apparatus employing an indexable web polishing station according to an embodiment of the present invention. 
         FIG. 5  is an underside view illustration of a carousel of a carousel CMP apparatus according to an embodiment of the present invention. 
         FIG. 6  is a side view of an exemplary embodiment of a CMP polishing station of the present invention. 
         FIG. 7  is a side view of an exemplary embodiment of a buffing/polishing station according to an embodiment of the present invention. 
         FIG. 8  is a block diagram of the method for polishing a wafer with the carousel CMP apparatus according to an embodiment of the present invention. 
         FIG. 9  is a top view illustration of another exemplary embodiment of a CMP apparatus employing orbiting indexable web polishing stations of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of exemplary embodiments only and is not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth. 
     A schematic representation of an exemplary embodiment of an indexable web polishing station  10  of the present invention is shown in  FIG. 1 . A polishing web  12  is provided with at least one side of web  12  having a fixed abrasive surface  14  (i.e., one onto which abrasives are fixedly mounted, formed or attached). One type of fixed abrasives that may be used with the present invention is discussed in detail in U.S. Pat. No. 5,958,794, issued Sep. 28, 1999 to Bruxvoort, et al., which is hereby incorporated by this reference. The web  12  preferably also has a smooth opposite surface  16  that may be laid across and supported by a supporting surface  18 . The web  12  is preferably 0.25 mm thick and may have at least one side, surface  14 , of the web  12  covered with microreplicated structures with fixed abrasives. The microreplicated structures may be randomly positioned on the web  12 , but preferably form a pattern. The minimum width of the web  12  is dependent on the size of the wafer W to be planarized. For example, a web  12  having a width of at least 300 mm is preferred for a wafer having a 200 mm diameter. An example of a method and apparatus for planarizing wafers using a polishing web is disclosed on U.S. Ser. No. 09/519,923, assigned to Speedfam-IPEC Corporation. One or more fluids (deionized water, slurry, etc.) may be applied through conduit  42  via a fluid pump (not shown). 
     The abrasive characteristics of web  12  tend to deteriorate very quickly, sometimes even during the planarization of a single wafer W. However, the short life of web  12  can be overcome by constructing the web  12  in a long sheet and only exposing an amount of web  12  necessary to planarize one wafer W. Web  12  may be advanced continuously, preferably automatically, so that the wafer W is exposed to fresh web  12  during the planarization process. Alternatively, web  12  may be advanced incrementally so that the wafer W is exposed to unused segment of web  12  at given periods during the planarization process. In a further alternative embodiment, after planarization of a wafer, web  12  may be advanced, either manually or, preferably, automatically so that a subsequent wafer to be planarized is subjected to a fresh, unused segment of web  12 . Web  12  may be indexed a predetermined amount, preferably between 5 mm and 300 mm, to expose fresh web  12  at indexable web polishing station  10 . If web  12  is of particularly high durability, or if the process used to planarize the previous wafers is sufficiently mild, it may be possible to only index web  12  after a certain number of wafers have been planarized. The amount and timing for indexing web  12  is highly dependent on the wafer planarization process being used. Factors such as the type and quality of web  12  used, the material on the wafer being planarized, the amount of material that is being removed from the wafer and the planarization quality necessary for the wafer all affect the amount and time required for indexing web  12 . 
     Web  12 , in the form of a long sheet, may advantageously be taken from a new roll cartridge  20  with the used web  12  being fed into, and stored by, a take-up cartridge  22 . The new roll cartridge  20  and take-up cartridge  22  allow a fresh web  12  to be exposed at the polishing station  10  by simply replacing the empty new roll cartridge  20  with a full new roll cartridge  20  and replacing the take-up cartridge  22 , containing the old web  12 , for an empty take-up cartridge  22 . Alternatively, after the long sheet of web  12  has been used, the web  12  may be taken from the take-up cartridge  22  and rewound back onto the new roll cartridge  20 . This would allow a fresh web  12  to be installed by simply replacing the new roll cartridge  20  containing the previously consumed web  12  with a “new” new roll cartridge  20  containing an unused web  12 . 
     The web  12 , in combination with a new roll cartridge  20  or take-up cartridge  22 , should be of suitable size to be housed within a housing  24  and should not be made so large or heavy as to make loading and unloading of the new roll cartridge  20  and take-up cartridge  22  difficult. However, the longer, and thus heavier, the web  12 , the fewer times the new roll cartridge  20  and take-up cartridge  22  will need to be replaced, thus increasing the CMP apparatus&#39; uptime and availability for use. If easy replacement is desired, web  12  may be made shorter; if longer periods of time are desired between web  12  replacement, web  12  may be made longer. 
     Web  12  with a fixed abrasive surface  14  has been found to give good within-die planarity by removing high spots quickly on structural semiconductor wafers W. The microreplicated structures on the web  12  are designed to contact the face of wafer W at the high spots on the face of wafer W, thus concentrating the abrasive action in these areas. A further advantage is that the removal rate of material slows as the face of wafer W becomes planarized. The pressure at surface contact points are reduced as the wafer&#39;s W face becomes more planar which reduces the rate of material removal. This is due to all the high spots on the face of wafer W being removed and thus more evenly distributing the abrasive action and down-force across the entire face of wafer W. 
     During planarization, wafer W is held by a wafer carrier  26 , which urges wafer W against web  12  with a desired amount of force. While wafer W is rotated by wafer carrier  26  about an axis  28 , indexable web polishing station  10  uses orbital motion to polish wafer W. Two rotatable shafts  30  and  32  are off-set from each other by the amount of a desired orbit. The radius of the orbit is preferably less than the radius of the wafer W. Shaft  30  may rotate in the direction indicated by arrow A 34  and shaft  32  may rotate at the same speed, but in the direction indicated by arrow A 36 . Eccentrics or cams (not shown) may be attached to shaft  32  to allow indexable web polishing station  10  to also dither (in one or more axes as indicated by arrows A 38  and A 40 ) while orbiting. An example of polishing a wafer by orbital motion is disclosed in U.S. Pat. No. 5,554,064, issued Sep. 10, 1996 to Breivogel et al., which patent is incorporated herein by reference. It is to be appreciated that a variety of other well-known means may be employed to facilitate the orbital motion of the indexable web in the present invention. 
     In an alternative embodiment, as illustrated in  FIG. 2 , an indexable web station  100  may comprise a new roll cartridge  102 , a first tension roller  104 , a first turnbar  106 , a second turnbar  108 , a second tension roller  110  and a take-up cartridge  112 . A web  114  may be threaded from new roll cartridge  102 , passing around a side of first tension roller  104 , around first turnbar  106 , across supporting surface  116 , around second turn bar  108 , passing around a side of second tension roller  110  and onto take-up cartridge  112 . First tension roller  104  and second tension roller  110  may be adjustable so that the tension of indexable web  114  may be increased or decreased as desired. It may be appreciated that while indexable web station  100  employs first tension roller  104  and second tension roller  110 , any suitable number of tension rollers may be employed to generate and maintain an appropriate amount of tension in web  114 . Further, web  114  may take a variety of paths through indexable web station  100  depending on the desired configuration and features desired to be interposed within the indexable web station. 
     In a further embodiment of the present invention, as shown in  FIG. 3 , an indexable web station  150  may be configured so that fluids, such as a slurry or deionized water may be distributed through an indexable web  152 . In contrast to rotating polishing stations, an orbiting polishing station provides the advantage that fluid may be supplied through the polishing station to the polishing surface, without the use of rotary unions or the like. A pump  154  may distribute the fluid through a distribution manifold  156  in the direction indicated by arrow A 158  to one or more conduits  162  formed within supporting surface  160 . Conduits  162  allow for easy transportation of the fluid through the supporting surface  160  as indicated by arrow A 168 . Conduits  162  may then distribute fluid to the top surface  164  of supporting surface  160 . Indexable web  152  is configured with a plurality of holes  166  through which the fluid may flow to reach the top surface of web  152 . In conventional applications, with the distribution system, the wafer typically acts like a squeegee preventing fluids from reaching the center of the wafer resulting in a nonuniform planarization process. This distribution system may be used to overcome the problem in the prior art of distributing fluids to the center of the wafer. In an alternative embodiment, pump  154  may distribute the fluid through distribution manifold  156  to one or more trenches formed on the top surface  164  of supporting surface  160 . The fluid flows through the trenches in the direction of arrow A 168  and through holes  166  of web  152 . 
     The indexable web station of the present invention may be used in a variety of CMP apparatus. For example, the indexable web station may be used in a carousel-type CMP apparatus, such as the one shown in  FIG. 4 . This CMP apparatus has a base unit  220  and a rotatable carousel  230 . Base unit  220  has a top surface  250  which surrounds three polishing stations, an indexable web polishing station  240  as described above, a conventional CMP polishing station  242 , and a buffing station  244 , and a wafer transfer station  260 . Base unit  220  supports a transparent walled cover  270  which surrounds polishing stations  240 ,  242  and  244  and wafer transfer station  260  to catch waste product thrown by the polishing stations during polishing. Walled cover  270  further houses multi-wafer-carrier carousel  230 , the number of wafer carriers of which may correspond to the number of polishing stations in addition to the wafer transport station. In the exemplary embodiment shown in  FIG. 4 , carousel  230  has four wafer carriers,  280   a ,  280   b ,  280   c  and  280   d . Wafer carriers  280   a –   280   d  receive and hold wafers W and polish them by pressing them against the respective polishing stations  240 ,  242  and  244 . Each of the wafer carriers are equally spaced about the center of carousel  230  to align vertically with polishing stations  240 ,  242  and  244 . Carousel  230  is supported by a center post  290  which is configured to permit carousel  230  to be rotated about its center axis by a motor (not shown) housed within base unit  220 . While three polishing stations and a transfer station are shown in this exemplary embodiment, it will be appreciated that more polishing stations and/or transfer stations, or only one or two polishing stations may be used in the CMP apparatus. Similarly, while four wafer carriers are shown, one, two, three, five or more carriers may be used to suitably correspond to the number of polishing stations and transfer stations that are used. 
     Each of the wafer carries  280   a –   280   d  is attached to the end of a cylindrical shaft  284  that is connected to a rotational drive mechanism by a gimbal assembly (not shown). When activated, the rotational drive mechanism causes the wafer carrier  280  to rotate about its own axis. In addition to rotation about their own axes, as shown in  FIG. 5 , wafer carriers  280   a–   280   d  are operatively connected to a carrier motor assembly (not shown) which may cause wafer carriers  280   a–   280   d  to translate radially along tracks  310  and laterally along tracks  320  formed in carousel  230 . Wafer carriers  280   a–   280   d  can rotate and translate independently as driven by their dedicated rotational drive mechanisms and carrier motor assemblies. 
     Each of the wafer carriers  280  has a wafer head  282 . The purposes of wafer head  282  is to help secure wafer W to wafer carrier  280  and also to prevent the wafer from becoming dislodged during planarization. Any of a number of different types of wafer heads can be used. For examples of suitable wafer heads, see the following patents, incorporated herein by this reference: U.S. Pat. No. 6,056,632, issued May 2, 2000 to Mitchel, et al.; U.S. Pat. No. 5,989,104, issued Nov. 23, 1999 to Kim, et al.; U.S. Pat. No. 6,024,630, issued Feb. 15, 2000 to Shendon et al.; U.S. Pat. No. 5,762,544, issued Jun. 9, 1998 to Zuniga et al.; U.S. Pat. No. 6,080,050, issued Jun. 27, 2000 to Chen et al; and U.S. Pat. No. 5,738,574, issued Apr. 14, 1998 to Tolles, et al. 
     Wafer carrier  280  may advance the wafer toward polishing stations  240 ,  242  and  244  and apply pressure such that the wafer engages the polishing surfaces of the polishing stations with a desired amount of force by a variety of mechanisms, for example, by expansion of a membrane assembly integral with wafer head  282 , as more fully disclosed in U.S. Pat. No. 6,056,632. Alternatively, wafer carrier  280  may be operatively connected to a pneumatic assembly (not shown) which moves shaft  284  vertically, thus advancing the wafer vertically down toward polishing stations  240 ,  242  and  244  for polishing and moving the wafer vertically up after polishing. 
     In use, as described below, the wafer carriers  280   a–   280   d  are each initially positioned above the wafer transfer station  260 . When the carousel  230  is rotated, it positions different wafer carriers  280   a–   280   d  over the polishing stations  240 ,  242  and  244  and the transfer station  260 . The carousel  230  allows each wafer carrier to be sequentially located first over the transfer station  260 , then over one or more of the polishing stations  240 ,  242  and  244  and then back to transfer station  260 . 
     Referring to  FIGS. 4 and 6 , CMP polishing station  242  includes a polishing platen  400  mounted for rotation by a drive motor (not shown). Alternatively, polishing platen  400  may be suitably configured for orbital motion, as described above. The polishing platen may be relatively large in comparison to wafer W so that, during the CMP process, wafer W may be moved across polishing platen  400  for planarizing and polishing wafer W. Polishing platen  400  may be formed of a hard incompressible material such as metal. 
     A polishing pad  420  is mounted to polishing platen  400 . In accordance with the present invention, a polishing pad  420  is used that is formed of a hard and low compressibility material to provide a flat planar contact surface  430  for planarizing the wafer W. According to the present embodiment, a hard polish pad IC1000 (product name) made by Rodele Nitta Company is used to polish wafer W, although it will be appreciated that any suitable polishing pad may be used. A polishing slurry containing an abrasive medium, such as silica or alumina, is deposited through a conduit  410  onto the surface of the polishing pad  420 . 
     Subsequent to planarizing wafer W with a hard low compressibility pad  420 , wafer W may be polished to remove microscratches formed by the indexable web and the hard pad. Referring to  FIGS. 4 and 7 , buffing station  244  includes a polishing platen  500  mounted for rotation by a drive motor (not shown). Alternatively, polishing platen  500  may be suitably configured for orbital motion, as described above. The polishing platen may be relatively large in comparison to wafer W so that, during buffing, wafer W may be moved across polishing platen  500  for buffing and polishing wafer W. A soft polish pad  520  is used to buff and polish wafer W. Soft polish pad  520  may be formed of a soft compressible material, such as blown polyurethane. A suitable polishing pad  520  may be obtained from Rodele Nitta Company and designated SUPREME (product name). One or more fluids (DI water, slurry, buffing solution, etc.) may be applied to polishing pad  520  through a conduit  540  via a fluid pump (not shown). 
     Next, with reference to  FIGS. 1 ,  4  and  8 , operations of the CMP apparatus thus structured using the indexable web polishing station of the present invention will be described. The description begins with the insertion of wafer W and continues with the subsequent movement of wafer carriers  280   a ,  280   b ,  280   c  and  280   d  supported by carousel  230 . 
     A first wafer W 1  is loaded from a loading apparatus (not shown) to transfer station  260 , which loads the wafer into wafer carrier  280   a . Carousel  230  is then rotated clockwise on center post  290  so as to position wafer carrier  280   a  and wafer W 1  over indexable web polishing station  240 . Indexable web polishing station  240  performs a first-stage polish of wafer W 1 . While indexable web polishing station  240  is polishing wafer W 1 , a second wafer W 2  is loaded from the loading apparatus to transfer station  260  and from there to wafer carrier  280   b , now positioned over transfer station  260 . 
     After the indexable web polishing of wafer W 1  is completed, and after wafer W 2  has been loaded into wafer carrier  280   b , carousel  230  is rotated clockwise so that wafer W 1  is positioned over conventional CMP polishing station  242 , wafer W 2  is positioned over indexable web polishing station  240 , and wafer carrier  280   c  is positioned over transfer station  260 . If new roll cartridge  20  contains sufficient unused web  12  to process another wafer, web  12  is advanced to expose an unused segment of web  12  at indexable web polishing station  240 . Alternatively, indexable web polishing station  240  may be configured so that web  12  is intermittently or continuously incremented during planarization of the wafers. 
     Indexable web polishing station  240  performs a first-stage polish of wafer W 2 , CMP polishing station  242  performs a second-stage CMP polishing of wafer W 1  and a third wafer W 3  is loaded from the loading apparatus to transfer station  260  and from there to wafer carrier  280   c , now positioned over transfer station  260 . 
     After the second-stage polishing of wafer W 1 , the first-stage polishing of wafer W 2  and loading of wafer W 3  into wafer carrier  280   c , carousel  230  is again rotated clockwise so that wafer W 1  is positioned over buffing station  244 , wafer W 2  is positioned over CMP polishing station  242 , wafer W 3  is positioned over indexable web polishing station  240 , and wafer carrier  280   d  is positioned over transfer station  260 . If new roll cartridge  20  contains sufficient unused web  12  to process another wafer, web  12  is advanced to expose an unused segment of web  12 . Indexable web polishing station  240  then performs a first-stage polish of wafer W 3 , CMP polishing station  242  performs a second-stage CMP polishing of wafer W 2 , buffing station  244  performs a third-stage buffing/polishing of wafer W 1  and a fourth wafer W 4  is loaded from the loading apparatus to transfer station  260  and from there to wafer carrier  280 d, now positioned over transfer station  260 . 
     After the third-stage polishing of wafer W 1 , the second-stage polishing of wafer W 2 , the first-stage polishing of wafer W 3  and the loading of wafer W 4  into wafer carrier  280   d , carousel  230  is rotated counterclockwise so that wafer carrier  280   a  and wafer W 1  are positioned above transfer station  260 , wafer carrier  280   b  and wafer W 2  are positioned above buffing station  244 , wafer carrier  280   c  and wafer W 3  are positioned above CMP polishing station  242  and wafer carrier  280   d  and wafer W 4  are positioned above indexable web polishing station  240 . Counterclockwise rotation back to carousel&#39;s  230  original starting position eliminates the need for rotary couplings to carousel  230 . Alternatively, carousel  230  may be configured to continue rotating in the clockwise direction so that wafer carrier  280   a  and wafer W 1  are positioned above transfer station  260 , wafer carrier  280   b  and wafer W 2  are positioned above buffing station  244 , wafer carrier  280   c  and wafer W 3  are positioned above CMP polishing station  242  and wafer carrier  280   d  and wafer W 4  are positioned above indexable web polishing station  240 . 
     If new roll cartridge  20  contains sufficient unused web  12  to process another wafer, web  12  is advanced to expose an unused segment of web  12 . Indexable web polishing station  240  then performs a first-stage polish of wafer W 4 , CMP polishing station  242  performs a second-stage CMP polishing of wafer W 3 , buffing station  244  performs a third-stage buffing/polishing of wafer W 2  and wafer W 1  is washed at the transfer station  260  by a washer (not shown) and is loaded from wafer carrier  280   a  back to the loading apparatus. A fifth wafer W 5  is then loaded onto transfer station  260  and then into wafer carrier  280   a . The process then repeats with clockwise rotation of carousel  230  after the first-, second- and third-stage polishings have been completed of wafers W 4 , W 3  and W 2 , respectively. 
     The indexable web polishing station of the present invention may also be used in an integrated, multiple polishing station system, such as the Avantgaard  776  CMP System by Speedfam-IPEC, Inc. Such multiple polishing station systems may have two or more polishing stations for performing CMP on wafers. Referring to  FIG. 10 , a multiple polishing station apparatus  600  is illustrated having four polishing stations  602 ,  604 ,  606  and  608 , although it will be appreciated that multiple polishing station  600  may have one, two or any other suitable number of polishing stations. Polishing stations  602 ,  604 ,  606  and  608  each may be indexable web polishing stations, according to the present invention, that are configured to move orbitally. 
     Indexable web polishing stations  602 ,  604 ,  606  and  608  are positioned within a base  610  having a top surface  612 . Top surface  612  is configured with a number of openings  614  to correspond to the number of polishing stations employed by multiple polishing station apparatus  600 . Openings  614  are large enough to permit the indexable web polishing stations to orbit without interference from base  610 . A wafer handling robot  616  is centered between the polishing stations and is configured to transport a wafer from a transfer station  618  to one of the polishing stations for polishing and back to the transfer station after polishing. 
     Multiple polishing station apparatus  600  employs wafer carriers (not shown), the number of which may correspond to the number of polishing stations. The wafer carriers receive wafers from the wafer handling robot  616  and hold the wafers and polish them by pressing them against the respective indexable web polishing stations  602 ,  604 ,  606  and  608 . Each of the wafer carriers aligns vertically with a corresponding polishing station and is attached to the end of a cylindrical shaft that is configured to rotate the wafer carriers and the wafer around a longitudinal axis of the shaft. In addition to rotation about the longitudinal axis, the wafer carriers may be configured to translate radially or otherwise oscillate. Alternatively, the wafer carriers may be suitably configured to move orbitally so that during polishing the wafer carrier and the indexable web polishing station both move orbitally, preferably in opposite directions. 
     During operation of multiple polishing station apparatus  600 , robot  616  receives a wafer W from transfer station  618 . Robot  616  then positions wafer W proximate to one of the polishing stations  602 ,  604 ,  606  or  608 . A wafer carrier aligned vertically about the respective polishing station receives wafer W from robot  616 . The wafer carrier then urges wafer W against an indexable web  620  of the indexable web polishing station. The wafer carrier presses wafer W against the indexable web  620  as it rotates or, alternatively, orbits. The indexable web polishing station orbits, as described above, to uniformly planarize and polish wafer W. After polishing of wafer W, the wafer carrier raises wafer W above the indexable web polishing station. Robot  616  then moves into a suitable position to receive wafer W from the wafer carrier. Robot  616  may then transport wafer W to a buffing station  622  for buffing of wafer W. After buffing of wafer W, robot  616  removes wafer W from buffering station  622  and back to transfer station  618 . If the new roll cartridge contains sufficient unused web to process another wafer, web  620  is advanced to expose an unused segment of web  620 . Alternatively, the indexable web polishing stations may be configured so that web  620  is intermittently or continuously incremented during planarization of the wafers. 
     While multiple polishing station apparatus  600  is illustrated in  FIG. 10  with all polishing stations  602 ,  604 ,  606  and  608  employing indexable web polishing stations, it will be appreciated that in an alternative embodiment only one of the multiple stations may employ an orbiting indexable web polishing station, with the other polishing stations employing any suitable polishing apparatus. For example, in one embodiment of the multiple polishing station  600 , only one indexable web polishing station may be employed, while the other polishing stations employ conventional rotating polishing platens. Accordingly, wafer W may be polished first at the indexable web polishing station and subsequently at a conventional CMP rotating or orbiting platen. In another embodiment, one orbital indexable web polishing station may be employed, while the other indexable web polishing stations do not orbit. 
     Although the subject invention has been described herein in conjunction with the appended drawing Figures, it will be appreciated that the scope of the invention is not so limited. Various modifications in the arrangement of the components discussed and the steps described herein for using the subject device may be made without departing from the spirit and scope of the invention as set forth in the appended claims.