Abstract:
In one aspect, a method for cleaning an edge of a substrate is provided. The method includes the steps of (a) supporting a substrate on a rotatable substrate support; (b) contacting an edge of the substrate with one or more rollers; (c) rotating the substrate support so as to rotate the substrate; and (d) rotating the one or more rollers so as to clean the edge of the substrate Numerous other aspects are provided.

Description:
[0001]     The present application claims priority from U.S. Provisional Patent Application Ser. No. 60/674,910, filed Apr. 25, 2005, which is hereby incorporated by reference herein in its entirety.  
       CROSS REFERENCE TO RELATED APPLICATION  
       [0002]     The present application is related to U.S. patent application Ser. No. ______, filed Apr. 24, 2006 and titled “METHODS AND APPARATUS FOR CLEANING AN EDGE OF A SUBSTRATE” (Attorney Docket No. 9861), which is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0003]     The present invention relates to semiconductor device fabrication, and more particularly to methods and apparatus for cleaning an edge of a substrate.  
       BACKGROUND OF THE INVENTION  
       [0004]     After chemical mechanical polishing, slurry residue conventionally is cleaned or scrubbed from substrate surfaces via a mechanical scrubbing device, such as a device which employs polyvinyl acetate (PVA) brushes, brushes made from other porous or sponge-like material, or brushes having bristles made from nylon or similar materials. Although these conventional cleaning devices may remove a substantial portion of the slurry residue which adheres to the edges of a substrate, slurry particles as well as photoresist or other pre-deposited and/or pre-formed layers nonetheless may remain and produce defects during subsequent processing.  
         [0005]     Accordingly a need exists within the field of substrate cleaning for methods and apparatus which effectively clean the edge surfaces of a substrate.  
       SUMMARY OF THE INVENTION  
       [0006]     In a first aspect of the invention, a first apparatus for cleaning an edge of a substrate is provided. The first apparatus includes (1) a substrate support adapted to support and rotate a substrate; and (2) one or more rollers positioned to contact an edge of a substrate supported by the substrate support. The one or more rollers are adapted to clean the edge of the substrate as the substrate support rotates the substrate relative to the one or more rollers.  
         [0007]     In a second aspect of the invention, a second apparatus for cleaning an edge of a substrate is provided. The second apparatus includes (1) one or more rollers of a first diameter adapted to contact an edge of a substrate and rotate the substrate; and (2) one or more rollers of a second diameter that is larger than the first diameter adapted to contact the edge of the substrate and to clean the edge of the substrate. The one or more rollers of the first diameter and the one or more rollers of the second diameter may be adapted to rotate at substantially the same speed. Numerous other aspects are provided.  
         [0008]     Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIGS. 1A and 1B  illustrate a top view and a side view, respectively, of a first exemplary edge cleaning apparatus provided in accordance with the present invention.  
         [0010]      FIG. 1C  is a front view of the first edge cleaning apparatus in which a single motor drives each roller.  
         [0011]      FIG. 2A  is a side view of a substrate showing a beveled edge region of the substrate and one or more rollers configured to clean the same in accordance with the present invention.  
         [0012]      FIG. 2B  is a side view of a roller having a flat surface for contacting a substrate in accordance with the present invention.  
         [0013]      FIG. 2C  is a side view of a roller having a grooved surface for contacting a substrate in accordance with the present invention.  
         [0014]      FIG. 3A  illustrates a top view of a roller in contact with a substrate during cleaning wherein the substrate and roller rotate in the same direction.  
         [0015]      FIG. 3B  illustrates a top view of a roller in contact with a substrate during cleaning wherein the substrate and roller rotate in opposite directions.  
         [0016]      FIGS. 4A and 4B  illustrate a top view and a side view, respectively, of a second exemplary edge cleaning apparatus provided in accordance with the present invention.  
         [0017]      FIG. 4C  is a front view of the second edge cleaning apparatus in which a single motor drives each roller.  
         [0018]      FIG. 5  is top view of an embodiment in which the second cleaning apparatus employs two drive rollers and two cleaning rollers.  
         [0019]      FIG. 6  is a top plan view of an exemplary embodiment of a planarization system provided in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]     In accordance with the present invention, one or more rollers may be employed to clean an edge of a substrate. Rotation of the substrate is independent and/or decoupled from edge cleaning. For example, in one embodiment of the invention, a substrate support stage is employed to support and rotate a substrate relative to one or more rollers so that the one or more rollers clean the edge of the substrate. In such an embodiment, each roller may be driven by the same motor to reduce cost and simplify implementation. Alternatively, a separate motor may be employed to rotate each roller.  
         [0021]     In a second embodiment of the invention, a substrate is rotated by one or more rollers of a first diameter, and cleaned by one or more rollers of a second, large diameter. As with the first embodiment of the invention, each roller may be driven by the same motor to reduce cost and simplify implementation. Alternatively, a separate motor may be employed to rotate each roller. These and other embodiments of the invention are described below with reference to  FIGS. 1A-6 .  
         [0022]      FIGS. 1A and 1B  illustrate a top view and a side view, respectively, of a first exemplary edge cleaning apparatus  100  provided in accordance with the present invention. With reference to  FIGS. 1A and 1B , the first edge cleaning apparatus  100  includes a substrate support  102  ( FIG. 1B ) adapted to support and rotate a substrate S, and a plurality of rollers  104   a - d  positioned to contact and clean an edge of the substrate S (as described further below). While four rollers  104   a - d  are shown in  FIGS. 1A-1B , it will be understood that fewer or more rollers may be used (e.g., 1, 2, 3, 5, 6, etc., rollers).  
         [0023]     In the embodiment of  FIGS. 1A and 1B , the substrate support  102  is rotated/driven by a first motor  106  and the rollers  104   a - d  are each rotated/driven by a separate motor  108   a - d . In another embodiment, each of the rollers  104   a - d  may be driven by the same motor. For example,  FIG. 1C  is a front view of the first edge cleaning apparatus  100  in which a single motor  108  drives each roller  104   a - d  (via a plurality of belts  110   a - d  coupled to respective shafts  112   a - d  of each roller  104   a - d , only two of which are shown in  FIG. 1C ). Note that such an implementation is less expensive and easier to implement. The substrate support  102  also may be driven by the motor  108  via appropriate belts and/or gearing.  
         [0024]     With reference again to  FIGS. 1A-1C , the first edge cleaning apparatus  100  may include a controller  114  that is adapted to control operation of the first edge cleaning apparatus  100 . For example, the controller  114  may be coupled to the first motor  106  and the motors  108   a - d  (or the motor  108  in the embodiment of  FIG. 4C ) and direct rotation of the substrate support  102  and rollers  104   a - d  as described further below. The controller  114  may include one or more microprocessors, microcontrollers, logic circuitry, a combination of the same, or any suitable hardware and/or software for controlling operation of the first edge cleaning apparatus  100 .  
         [0025]     In at least one embodiment of the invention, the rollers  104   a - d  may be adapted to move along the edge of the substrate S to more effectively clean the substrate S. For example,  FIG. 2A  is a side view of the substrate S showing a beveled edge region  200  of the substrate S. As shown in  FIG. 2A , the roller  104   a  is adapted to pivot from contact with the outer edge  202  of the substrate S into contact with a top bevel  204  of the substrate S or into contact with a bottom bevel  206  of the substrate S (as indicated by reference numerals  104   a ′ and  104   a ″, respectively). The rollers  104   b - c  may be similarly configured.  
         [0026]     As further shown in  FIG. 2A , one or more stationary rollers may be positioned so as to clean the top bevel  204  of the substrate S and/or the bottom bevel  206  of the substrate S as indicated by rollers  104   c ′,  104   c ″. In one embodiment, at least one roller may be positioned similar to roller  104   a  in  FIG. 2A  to clean an outer edge of the substrate S, at least one roller may be positioned similar to roller  104   c ′ in  FIG. 2A  to clean a top bevel of the substrate S and at least one roller may be positioned similar to roller  104   c ″ in  FIG. 2A  to clean a bottom bevel of the substrate S.  
         [0027]     Each roller  104   a - d  may have any shape suitable for cleaning the edge region  200  of the substrate S. For example,  FIG. 2B  is a side view of a roller  104   a  having a flat surface  208  for contacting the substrate S; and  FIG. 2C  is a side view of a roller  104   a  having a grooved surface  210  for contacting the substrate S. The flat surface  208  may be more effective at cleaning the outer edge  202  ( FIG. 2A ) of the substrate S, while the grooved surface  210  may be more effective at cleaning the beveled edges  204 ,  206  of the substrate S. Any other roller shapes may be used for the rollers  104   a - d , as may combinations of roller shapes.  
         [0028]     The rollers  104   a - d  may be formed from any material that effectively cleans the edge of the substrate S. For example, if a cleaning chemistry is to be employed during edge cleaning, a soft roller material such as polyvinyl acetate (PVA) or the like may be used for one or more of the rollers  104   a - d . However, if edge cleaning is to be predominately friction based (e.g., polishing), a harder roller material such as a fixed abrasive (e.g., a diamond impregnated polymer or metal matrix or another fixed abrasive), silicon carbide, etc., may be used for one or more of the rollers  104   a - d .  
         [0029]     In at least one embodiment of the invention, the drive rollers  104   a - d  have a diameter of about 1-5 inches. Other roller sizes may be used.  
         [0030]     In operation, to clean the edge of the substrate S, the substrate S is placed on the substrate support  102  as shown in  FIGS. 1A-1C . For example, the substrate S may be held against the substrate support  102  by vacuum, an electrostatic potential or by any other suitable chucking technique. Note that the rollers  104   a - d  may be retracted during placement of the substrate S onto the substrate support  102 , and then brought into contact with the substrate S (as shown). The controller  114  may be adapted to control substrate placement and/or retraction of the rollers  104   a - d.    
         [0031]     Once the substrate S has been placed on and held by the substrate support  102 , the controller  114  may direct the motor  106  to rotate the substrate S. Such rotation may occur before, during or after the rollers  104   a - d  contact the substrate S. In one embodiment, a substrate rotation rate of about 5 to 100 rotations per minute (RPM), and in one embodiment about 50 RPM, may be used for a 300 mm substrate. Other rotation rates may be used.  
         [0032]     Before, during or after the substrate S begins to rotate, the controller  114  may direct the motors  108   a - d  (or the motor  108  in  FIG. 1C ) to rotate each roller  104   a - d . In one embodiment, a roller rotation rate of about 1 to 500 rotations per minute (RPM) may be used for a 300 mm substrate. Other rotation rates may be used. In at least one embodiment, a positive pressure, such as less than about 20 psi, may be exerted against the substrate S by the rollers  104   a - d . Other pressures may be used.  
         [0033]     The rotation rates and/or directions of the substrate S and the rollers  104   a - d  are selected such that at the point (or points) of contact between each roller  104   a - d  and the substrate S, each roller  104   a - d  and the substrate S have a different tangential velocity. In this manner, sliding contact occurs between each roller  104   a - d  and the substrate S, and the edge of the substrate S is cleaned (e.g., by mechanical polishing or by chemically assisted polishing if a cleaning chemistry is employed). Cleaning may continue until any material to be removed from the edge of the substrate S has been removed.  
         [0034]     In one embodiment of the invention, the substrate S and the rollers  104   a - d  are rotated in the same direction. For example,  FIG. 3A  illustrates a top view of the roller  104   c  in contact with the substrate S during cleaning wherein the substrate S and roller  104   c  rotate in the same direction as indicated by arrows  300  and  302 . When the rollers  104   a - d  and substrate S rotate in the same direction, the tangential velocities of the rollers  104   a - d  and the substrate S are in opposite directions as shown by arrows  304  and  306  in  FIG. 3A , producing a large frictional force between each roller  104   a - d  and the substrate S at their point of contact.  
         [0035]     In another embodiment of the invention, the substrate S and the rollers  104   a - d  are rotated in opposite directions. For example,  FIG. 3B  illustrates a top view of the roller  104   c  in contact with the substrate S during cleaning wherein the substrate S and roller  104   c  rotate in opposite directions as indicated by arrows  308  and  310 . When the rollers  104   a - d  and substrate S rotate in opposite directions, the tangential velocities of the rollers  104   a - d  and the substrate S are in the same direction as shown by arrows  312  and  314 . Accordingly, the difference in tangential speed of the rollers  104   a - d  and the substrate S at their point of contact determines the frictional force generated between the rollers  104   a - d  and the substrate S.  
         [0036]      FIGS. 4A and 4B  illustrate a top view and a side view, respectively, of a second exemplary edge cleaning apparatus  400  provided in accordance with the present invention. With reference to  FIGS. 4A and 4B , the second edge cleaning apparatus  400  includes a substrate support  402  ( FIG. 1B ) adapted to support, but not actively rotate, a substrate S. The second cleaning apparatus  400  further includes a first plurality of drive rollers  404   a - c  positioned to contact and rotate the substrate S, and at least one additional cleaning roller  405  that has a larger radius than the drive rollers  404   a - c  (as described further below). While three drive rollers  404   a - c  are shown in  FIGS. 4A-4B , it will be understood that fewer or more drive rollers may be used (e.g., 1, 2, 4, 5, 6, etc., drive rollers). Likewise, more cleaning rollers may be used (e.g., 2, 3, 4, etc., cleaning rollers).  
         [0037]     In the embodiment of  FIGS. 4A and 4B , the substrate support  402  is not rotated/driven by a motor. However, the substrate support  402  may rotate freely, such as under the influence of the drive rollers  404   a - c . Each drive roller  404   a - c  is shown as each being rotated/driven by a separate motor  408   a - c , and the cleaning roller  405  is shown as being rotated/driven by a motor  409 . In another embodiment, each of the drive rollers  404   a - c  and the cleaning roller  405  may be driven by the same motor. For example,  FIG. 4C  is a front view of the second edge cleaning apparatus  400  in which a single motor  408  drives each roller  404   a - c ,  405  (via a plurality of belts  410   a - d  coupled to respective shafts  412   a - d  of each roller, only two of which are shown in  FIG. 1C ). Note that such an implementation is less expensive and easier to implement.  
         [0038]     As stated, more than one cleaning roller  405  may be employed by the second cleaning apparatus  400 . For example,  FIG. 5  is top view of an embodiment in which the second cleaning apparatus  400  employs two drive rollers  404   a - b  and two cleaning rollers  405   a - b . Other numbers of drive rollers and/or cleaning rollers may be used.  
         [0039]     With reference again to  FIGS. 4A-5 , the second edge cleaning apparatus  400  may include a controller  414  that is adapted to control operation of the second edge cleaning apparatus  400 . For example, the controller  414  may be coupled to the motors  408   a - c ,  409  (or the motor  408  in the embodiment of  FIG. 4C ) and direct rotation of the drive rollers  404   a - c  and the cleaning roller  405  as described further below. The controller  414  may include one or more microprocessors, microcontrollers, logic circuitry, a combination of the same, or any suitable hardware and/or software for controlling operation of the second edge cleaning apparatus  400 .  
         [0040]     In at least one embodiment of the invention, the cleaning roller(s)  405  may be adapted to move along the edge of the substrate S to more effectively clean the substrate S as described previously with reference to  FIG. 2A  and the roller  104   a . Likewise, one or more stationary cleaning rollers may be positioned so as to clean the top bevel of the substrate S and/or the bottom bevel of the substrate S as previously described with reference to the rollers  104   c ′,  104   c ″ of  FIG. 2A . In one embodiment, at least one cleaning roller may be positioned to clean an outer edge of the substrate S, at least one cleaning roller may be positioned to clean a top bevel of the substrate S and at least one cleaning roller may be positioned to clean a bottom bevel of the substrate S (see  FIG. 2A ).  
         [0041]     Each cleaning roller  405  may have any shape suitable for cleaning the edge region of the substrate S. For example, each cleaning roller  405  may have a flat surface similar to the flat surface  208  of the roller  104   a  shown in  FIG. 2B ; or a grooved surface similar to the grooved surface  210  of the roller  104   a  shown in  FIG. 2C . A flat surface may be more effective at cleaning the outer edge of the substrate S, while a grooved surface may be more effective at cleaning the beveled edges of the substrate S. Any other roller shapes may be used for the drive rollers  404   a - c  and/or the cleaning roller(s)  405 , as may combinations of roller shapes.  
         [0042]     The cleaning roller(s)  405  may be formed from any material that effectively cleans the edge of the substrate S. For example, if a cleaning chemistry is to be employed during edge cleaning, a soft roller material such as polyvinyl acetate (PVA) or the like may be used for one or more of the cleaning rollers  405 . However, if edge cleaning is to be predominately friction based (e.g., polishing), a harder roller material such as a fixed abrasive (e.g., a diamond impregnated polymer or metal matrix or another fixed abrasive), silicon carbide, etc., may be used for one or more of the cleaning rollers  405 . The drive rollers  404   a - c  may be formed from polyeurethane, rubber or any other suitable material.  
         [0043]     In at least one embodiment of the invention, the drive rollers  404   a - c  have a diameter of about 1-5 inches, and the cleaning rollers  405  have a diameter of about 2-10 inches. Other drive and/or cleaning roller sizes may be used. In other embodiments, each cleaning roller may have a smaller size than the drive rollers.  
         [0044]     In operation, to clean the edge of the substrate S, the substrate S is placed on the substrate support  402  as shown in  FIGS. 4A-4C . For example, the substrate S may be held against the substrate support  402  by vacuum, an electrostatic potential or by any other suitable chucking technique. In some embodiments, the substrate S may not be chucked by the substrate support  402 , and may be allowed to move laterally relative to the substrate support  402 . In still other embodiments, the substrate support  402  may be eliminated (e.g., the rollers  404   a - c  and/or  405  may support the substrate S). Note that the rollers  404   a - c ,  405  may be retracted during placement of the substrate S onto the substrate support  402 , and then brought into contact with the substrate S (as shown). The controller  414  may be adapted to control substrate placement and/or retraction of the rollers  404   a - c ,  405 .  
         [0045]     Once the substrate S has been placed on and held by the substrate support  402 , the controller  414  may direct the motors  408   a - c  (or  408  in  FIG. 4C ) to rotate the rollers  404   a - c  so as to rotate the substrate S. Such rotation may occur before, during or after each cleaning roller(s)  405  contact(s) the substrate S. In one embodiment, a substrate rotation rate of about 5 to 100 rotations per minute (RPM), and in one embodiment about 50 RPM, may be used for a 300 mm substrate. Other rotation rates may be used.  
         [0046]     Before, during or after the substrate S begins to rotate, the controller  414  may direct the motor  409  (or the motor  408  in  FIG. 1C ) to rotate each cleaning roller  405 . In one embodiment, a cleaning roller rotation rate of about 1 to 500 rotations per minute (RPM) may be used for a 300 mm substrate. For example, the same rotation rate may be used for the drive and cleaning rollers as described further below. Other rotation rates may be used. In at least one embodiment, a positive pressure, such as less than 20 psi, may be exerted against the substrate S by the rollers  104   a - d . Other pressures may be used.  
         [0047]     The rotation rates and/or directions of the substrate S and the rollers  404   a - c ,  405  are selected such that at the point (or points) of contact between each cleaning roller  405  and the substrate S, each cleaning roller  405  and the substrate S have a different tangential velocity. In this manner, sliding contact occurs between each cleaning roller  405  and the substrate S, and the edge of the substrate S is cleaned (e.g., by mechanical polishing or by chemically assisted polishing if a cleaning chemistry is employed). Cleaning may continue until any material to be removed from the edge of the substrate S has been removed.  
         [0048]     In one embodiment of the invention, the drive rollers  404   a - c  and the cleaning roller(s)  405  are rotated in opposite directions such that the substrate S and the cleaning roller(s)  405  are rotated in the same direction (in a manner similar to that shown in  FIG. 3A  with reference to the roller  104   c ). When the cleaning roller(s)  405  and substrate S rotate in the same direction, the tangential velocities of the cleaning roller(s)  405  and the substrate S are in opposite directions (see arrows  304  and  306  in  FIG. 3A ), producing a large frictional force between each cleaning roller  405  and the substrate S at their point of contact.  
         [0049]     In another embodiment of the invention, the drive rollers  404   a - c  and the cleaning roller(s)  405  are rotated in the same direction such that the substrate S and the cleaning roller(s)  405  are rotated in opposite directions (in a manner similar to that shown in  FIG. 3B  with reference to the roller  104   c ). When the cleaning roller(s)  405  and substrate S rotate in opposite directions, the tangential velocities of the cleaning roller(s)  405  and the substrate S are in the same direction at the point of contact between the cleaning roller(s)  405  and the substrate S (see arrows  312  and  314  in  FIG. 3B ). Accordingly, the difference in tangential speed of the cleaning roller(s)  405  and the substrate S at their point of contact determines the frictional force generated between the cleaning roller(s)  405  and the substrate S. Because the drive rollers  404   a - c  and the cleaning roller(s)  405  have different diameters, the drive rollers  404   a - c  and cleaning roller(s)  405  may be rotated at the same speed (and in the same direction) and still produce different tangential velocities for the substrate S and the cleaning roller(s)  405  at the point of contact therebetween. Accordingly, the implementation of such an embodiment is simplified since a single motor may be employed to drive the drive rollers  404   a - c  and the cleaning roller(s)  405 .  
         [0050]      FIG. 6  is a top plan view of an exemplary embodiment of a planarization system  600 . The planarization system  600  includes a processing subsystem  602  coupled to a factor interface  604 . The processing subsystem  602  may be similar to a Mirra Mesa™ planarization system manufactured by Applied Materials, Inc. (e.g., a 200 mm substrate planarization tool) and described in U.S. patent application Ser. No. 09/547,189, filed Apr. 11, 2000 and titled “METHOD AND APPARATUS FOR TRANSFERRING SEMICONDUCTOR SUBSTRATES USING AN INPUT MODULE”, which is hereby incorporated by reference herein in its entirety, or another similar system.  
         [0051]     The processing subsystem  602  includes a robot  606  that is movable along a track  608 , an input shuttle (not separately shown), a polishing system  612  and a cleaning system  614 . The polishing system  612  includes a load cup (not separately shown), a first polishing platen  618   a  (e.g., a bulk polishing platen), a second polishing platen  618   b  (e.g., an endpoint on barrier layer polishing platen) and a third polishing platen  618   c  (e.g., a barrier layer buff polishing platen). The cleaning system  614  includes an input module  620   a , a megasonic module  620   b , a scrubber module  620   c , and an output module  620   d . Other types of polishing platens and/or cleaning techniques/arrangements may be employed.  
         [0052]     The processing system  602  also includes an edge cleaning module  622  and a rinsing device  624 . The edge cleaning module  622  may include any of the edge cleaning apparatus described herein with reference to  FIGS. 1A-5 . The rinsing device  624  may include, for example, a spin rinse dryer or similar rinsing device.  
         [0053]     Factory interface  604  includes a buffer chamber  626 , a substrate handler  628  located within the buffer chamber  626  and a plurality of loadports  630   a - d  coupled to the buffer chamber  626 . In general, any number of substrate handlers and/or loadports may be employed within the factory interface  604 , and other configurations may be used.  
         [0054]     In operation, a cassette of substrates may be placed on one of the loadports  630   a - d , and the substrate handler  628  may extract a substrate from the cassette. The substrate handler  628  then may transfer the substrate to the robot  606 , and the robot  606  may deliver the substrate to the polishing system  612 . After the substrate has been polished within the polishing system  612 , the robot  606  may transfer the substrate to the input module  620   a , and the substrate may be cleaned using the megasonic module  620   b  and/or scrubber module  620   c . Thereafter, the robot  606  may transfer the substrate to the edge cleaning apparatus  622  and edge/bevel cleaning may be performed as described previously with reference to  FIGS. 1A-5 . Following edge cleaning, the substrate may be transferred to and cleaned within the rinsing device  624  and returned to a substrate cassette via the robot  606  and/or the substrate handler  628 .  
         [0055]     The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the present invention may be employed to remove slurry residue from substrate edges, as well as photoresist or other pre-formed and/or pre-deposited films or layers.  
         [0056]     While the present invention has been described as employing one or more rollers to clean and/or polish material from the bevel and/or edge region of a substrate, a fixed abrasive material, such as a fixed abrasive tape, also may be employed to contact an edge of a substrate as the substrate is rotated (e.g., whether the substrate is rotated by a substrate support, one or more drive rollers or another mechanism). In one embodiment, a stationary fixed abrasive such as a fixed abrasive tape may be indexed (e.g., moved up or down relative to a horizontal substrate or moved to the right or left relative to a vertical substrate) so as to introduce new fixed abrasive material during cleaning of a substrate and/or during cleaning of subsequent substrates. For example, after a pre-determined number of substrates have been cleaned, the fixed abrasive tape may be moved so as to introduce new fixed abrasive material to the edge of substrates to be cleaned. Indexing may be periodic and/or on an as-need basis.  
         [0057]     Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.