METHODS AND APPARATUS TO CONTROL SUBSTRATE BEVEL AND EDGE POLISHING PROFILES OF FILMS

Abstract

Methods and apparatus are provided for polishing a film on an edge of a substrate. In some embodiments, a polishing head is provided having a backing plate adapted to press polishing material against a film on an edge of a substrate. The backing plate has a profiled portion adapted to provide a pre-set film profile. Numerous other aspects are provided.

Description

FIELD OF THE INVENTION

The present invention relates generally to substrate processing, and more particularly to methods and apparatus for controlling substrate edge film profiles.

BACKGROUND OF THE INVENTION

Substrates are used in electronic device manufacturing. During processing, a film may be deposited on the surface of a substrate. However, it may be undesirable to have this film on the edge of the substrate. As such, methods and apparatus adapted to partially or completely remove films from an edge of a substrate are desired.

SUMMARY OF THE INVENTION

In aspects of the invention, an apparatus is provided for polishing a film on an edge of a substrate. The apparatus comprises a polishing head having a backing plate adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profiled portion adapted to provide a pre-set film profile during polishing.

In other aspects of the invention, a system for polishing a film on an edge of a substrate is provided. The system comprises a substrate support, adapted to support and rotate a substrate; a polishing head having a backing plate adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profiled portion adapted to provide a pre-set film profile during polishing; and a controller adapted to operate the movement of the polishing head.

In yet other aspects of the invention, a method for polishing a film on an edge of a substrate is provided. The method comprises selecting a rocking start angle and a rocking end angle for a profiled backing plate; contacting a film on an edge of a substrate with the backing plate; and rocking the backing plate against the film on the substrate edge during polishing.

In another aspect of the invention, a backing plate is provided that is adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profiled portion adapted to provide a pre-set film profile during polishing. Numerous other aspects are provided.

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 FIGURES

FIG. 1 is a schematic illustration of a cross-section of a portion of a substrate.

FIG. 2 is a schematic plan view of an example embodiment of a system for polishing parts of a substrate according to the present invention.

FIG. 3 is a schematic perspective view depicting an embodiment of a polishing apparatus for polishing a substrate according to the present invention.

FIG. 4 is a schematic perspective view of an exemplary embodiment of a polishing apparatus including a backing plate according to the present invention.

FIG. 5A is a schematic cross-sectional view depicting an example embodiment of a backing plate according to the present invention.

FIG. 5B is an illustration of the backing plate shown in FIG. 5A according to the present invention.

FIG. 6A is a schematic cross-sectional view depicting an alternative example embodiment of a backing plate according to the present invention.

FIG. 6B is an illustration of the backing plate shown in FIG. 6A according to the present invention.

FIG. 7 is a schematic cross-sectional view depicting an additional example embodiment of a backing plate according to the present invention.

FIG. 8 is a flowchart describing the application of an example embodiment of the present invention.

DETAILED DESCRIPTION

The present invention provides improved methods and apparatus for polishing the edge of a substrate. In the present application, the term “polish” is used to mean wearing away of a layer of film deposited on the substrate. The wearing away may be partial, such that a thinner layer of film remains or may be complete, such that no film remains. The present invention provides a backing plate having a shape that substantially matches a desired film shape to remain at the substrate edge. Backing plates having different shapes may be used, depending on the desired film profile. The backing plate may also be rocked against the film to achieve the desired film profile. In some embodiments, the backing plate may press a backing pad against the film on the substrate to optimize film removal.

With reference to FIG. 1, a substrate 100 may include two major surfaces 102, 102′ and an edge 104. Each major surface 102, 102′ of the substrate 100 may include a device region 106, 106′ and an exclusion region 108, 108′. (Typically however, only one of the two major surfaces 102, 102′ will include a device region and an exclusion region.) The exclusion regions 108, 108′ may serve as buffers between the device regions 106, 106′ and the edge 104. The edge 104 of a substrate 100 may include an outer edge 110 and bevels 112, 114. The bevels 112, 114 may be located between the outer edge 110 and the exclusion regions 108, 108′ of the two major surfaces 102, 102′. The substrate 100 may have a film 116 deposited on at least one major surface 102 and the edge 104, including at least one bevel 112 and the outer edge 110 during processing. The present invention is adapted to polish the outer edge 110 and at least one bevel 112, 114 of a substrate 100 without affecting the device regions 106, 106′. In some embodiments, all or part of the exclusion regions 108, 108′ may be cleaned or polished as well.

FIG. 2 is a perspective view depicting an exemplary embodiment of a substrate polishing system 200 according to the present invention. The system 200 of FIG. 2 may be adapted to polish a substrate 100, including, for example, the substrate edge 104. In an edge polishing process, the substrate edge 104 may be polished to remove defects or contaminants, to reduce film thickness and more generally to improve surface uniformity.

The system 200 shown herein includes three polishing heads 202 which, in turn, may each be part of a plurality of polishing apparatus 204 for cleaning and polishing the above-mentioned parts of the substrate 100. Any number and type of polishing heads 202 may be used in any practicable combination. The apparatus 204 may be supported by a frame. The frame may be constructed from any practicable materials such as aluminum, stainless steel, etc. In addition, in such multi-head embodiments, each head 202 may use a differently contoured backing plate 316 (FIG. 3) (e.g., parallel or perpendicular to the backing plate rocking plane, different shaped cut-off joints, different widths for the flat region, etc.). Any number of heads 202 may be used concurrently, individually, and/or in any sequence. The heads 202 may be disposed in different positions, and in different orientations (e.g., aligned with the substrate edge 104, normal to the substrate edge 104, angled relative to the substrate edge 104, etc.), to allow the polishing heads 202 (and backing pads and/or polishing tape described further below) to polish different portions of the substrate edge 104. The substrate 100 may be stationary or rotate as it is polished.

In some embodiments, one or more of the heads 202 may be adapted to be oscillated or moved (e.g., be angularly translated about a tangential axis of the substrate 100 and/or circumferentially relative to the substrate 100) around or along the substrate edge 104 by any suitable means so as to polish different portions of the substrate 100. In some embodiments, one or more of the heads 202 may continuously oscillate around or along the rotating edge 104 of the substrate 100. Different heads 202 may be used for different substrates 100, different types of substrates 100, or different polishing operations.

As shown herein, substrate polishing may be performed using one or more polishing apparatuses 204. In one or more embodiments, a plurality of polishing apparatuses 204 may be employed, in which each polishing apparatus 204 may have similar or different characteristics and/or mechanisms. In the latter case, particular polishing apparatuses 204 may be employed for specific operations. For example, one or more of a plurality of polishing apparatuses 204 may be adapted to perform relatively rough polishing and/or adjustments while another one or more of the plurality of polishing apparatus 204 may be adapted to perform relatively fine polishing and/or adjustments. Polishing apparatuses 204 may be used in sequence so that, for example, a rough polishing procedure may be performed initially and a fine polishing procedure may be employed subsequently to make adjustments to a relatively rough polish as needed or according to a polishing recipe. The plurality of polishing apparatuses 204 may be located in a single chamber or module, as shown herein, or alternatively, one or more polishing apparatuses may be located in separate chambers or modules. Where multiple chambers are employed, a robot or another type of transfer mechanism may be employed to move substrates 100 between the chambers so that polishing apparatuses 204 in the separate chambers may be used in series or otherwise.

The system 200 may also include a programmed and/or user operated controller 206. The controller 206 may direct the operation and movement of the one or more heads 202, as well as the other system components, as will be further described below.

FIG. 3 is a schematic perspective view of an embodiment of a polishing apparatus 300 for polishing a substrate edge 104. The polishing apparatus 300 may include a substrate driver 302 (e.g., a servomotor, gear, belt, chain, etc.), which may be mounted on a pedestal 304. A support 306 (e.g., a vacuum chuck) may be coupled (e.g., rigidly) to a shaft (not shown) of the substrate driver 302. The support 306 may support a substrate 100, for example. The substrate driver 302 may rotate the substrate 100, via the support 306, about a center 308 of the substrate 100 or another suitable axis. The substrate driver 302 may be connected to a substrate driver control unit (not shown) and/or the controller 206, which may control the angular displacement, angular velocity, and/or angular acceleration of the substrate 100. The polishing apparatus 300 may further include a polishing arm 310 aligned in the horizontal plane approximately tangential to the edge 104 (shown in FIG. 1) of the substrate 100 and supported by a frame 312. In other embodiments, the polishing arm 310 may be aligned differently, for example, vertically or at an angle with respect to the horizontal plane. The polishing arm 310 may include a polishing head section 314 (‘head’). The polishing head 314 may include a backing plate 316. A backing pad 318, for example, may cover the backing plate 316. In some embodiments the backing pad 318 may include an abrasive surface adapted to polish the substrate edge 104. The backing pad 318 may also be used to further lower the local pressure on the substrate 100 and increase the conformity of the backing plate 316 to a particular film profile. The backing plate 316 may be moved toward or away from the substrate 100 by an actuator (e.g., hydraulic actuator, pneumatic actuator, servomotor, etc.) (not shown). In some embodiments, polishing tape 320, may wrap around the polishing head 314, and over the backing plate and pad 316, 318, and be tensioned between spools 322, 324. The spools 322, 324 may be driven by spool drivers 326, 328 (e.g., servomotors), respectively. The spool drivers 326, 328, may be indexed to precisely control the amount of the polishing tape 320 that is advanced over the polishing head 314 from, for example, spool 322 to spool 324 in order to polish the substrate edge 104. In other embodiments, a polishing pad or other polishing material may be employed in place of the polishing tape 320.

In some embodiments, the backing pad 318 may be pushed against the substrate 100, via the backing plate 316, with an amount of force ranging from about 0.5 lbs. to about 2.0 lbs. Other amounts of force may be used. The backing pad 318 may be soft and/or include or develop contours to conform with a desired film profile. The tight contact between the backing pad 318 and the substrate edge 104 combined with the particular rotation speed of the substrate 100, may provide relative movement between the backing pad 318 and the substrate edge 104, resulting in polishing of the film 116 deposited on the substrate edge 104.

In some embodiments, the substrate 100 may contact the backing pad 318 for about 15 to 150 seconds depending on the resiliency of the pad selected, the rate of rotation, and/or the amount of polishing required. More or less time may be used. Depending on the amount of force applied by the actuator and the resiliency of the pad selected, for example, a controlled amount of pressure may be applied to the film 116. Other parameters may be used to control the applied pressure.

The backing pad 318 may be made of material such as, for example, an acetal resin (e.g., Delrin® manufactured by DuPont Corporation), PVDF, polyurethane closed cell foam, silicon rubber, etc. Other suitable materials may be used. Such materials may have resilience or an ability to conform that is a function of the thickness or density of the pad. The material may be selected based upon its resilience. The desired resilience may be selected based upon the type of polishing required. In some embodiments, the backing pad 318 may have an adjustable amount of ability to conform to the substrate's edge 104, such as by including an inflatable bladder.

In one or more embodiments, the polishing tape 320 and/or the backing pad 318 may be made from and/or include many different materials, such as aluminum oxide, silicon oxide, silicon carbide, etc. Other materials may also be used. In some embodiments, abrasives used may range from about 0.5 microns up to about 3 microns in size, although other sizes may be used. Different widths of polishing tape 320 ranging from about 0.2 inches to about 1.5 inches may be used, although other polishing tape widths may be used. In one or more embodiments, the polishing tape 320 may be about 0.002 to about 0.02 inches thick and withstand about 1 to 5 lbs. in tension. Other tapes having different thicknesses and tensile strengths may be used. The spools 322, 324 may have a diameter of approximately 1 inch and be capable of holding about 500 inches of polishing tape 320 or may be a diameter of approximately 3 inches and be capable of holding about 30,000 inches of polishing tape. Other spool dimensions may be used. The spools 322, 324 may be constructed from materials such as polyurethane, polyvinyl difluoride (PVDF), etc. Other materials may also be used.

In some embodiments, as the substrate 100 rotates, the polishing head 314 may rock around the substrate edge 104 to polish the entire edge 104. In operation, this may be achieved by angularly translating the head 314 and consequently, the backing plate 316 and backing pad 318 in contact with, and contoured to, the edge 104 of the substrate 100, around an axis that is tangential to the outer edge 110 of the substrate 100 as the substrate 100 is rotated. In some embodiments, the head 314 may be adapted to continuously or intermittently oscillate between the various positions. The head 314 may be moved by drivers (not shown) under the direction of the controller 206 (FIG. 2). Alternatively, the head 314 may be fixed and/or only adjusted while the substrate 100 is not being rotated. In yet other embodiments, the substrate 100 may be held fixed while the head 314 is oscillated (as described above) as well as rotated circumferentially around the substrate 100.

In some embodiments, the substrate 100 may be rotated in a horizontal plane. The substrate edge 104 may be aligned with, or normal to, the backing pad 318 (and backing plate 316) and/or polishing head 314. In additional or alternative embodiments, the substrate 100 may be rotated in a vertical plane, another non-horizontal plane, and/or be moved between different planes of rotation. The substrate 100 may be rotated at a rate ranging from about 50 to 300 RPM, for example, although other rates may be used.

Additionally or alternatively, the present invention may include facilities (e.g., a spray nozzle or bar) to deliver fluids to the substrate edge 104 being polished. In some embodiments, one or more channels may be provided, to direct chemicals or water to the substrate edge 104 to assist in the polishing and/or to wash away particles resulting from the polishing. The chemicals may be sprayed directly onto the substrate 100, at the substrate/backing pad interface, and/or may be applied to and/or through the backing pad 318. In some embodiments, sonic (e.g., megasonic) nozzles may be used to deliver sonicated fluids to the substrate edge 104 to supplement the cleaning. The fluids may be sprayed from either or both sides of the substrate 100 and the present invention may employ gravity or suction to cause the runoff not to contaminate or contact other parts of the substrate 100 or apparatus of the invention. Further, energy (e.g., megasonic energy) may be applied to the substrate edge 104 via fluid carrying such energy.

As described above, in some embodiments, the controller 206 (e.g., a programmed computer, a programmed processor, a gate array, a logic circuit, an embedded real time processor, etc.) may control the driver(s) used to rotate the substrate 100 and the actuator used to push the backing plate 316 and backing pad 318 against the film 116 on the substrate edge 104. Note that the controller 206 may be coupled (e.g., electrically, mechanically, pneumatically, hydraulically, etc.) to each of a plurality of actuators. Likewise, operation of the fluid channels may also be under the direction of the controller 206. Under direction of the controller 206, various fluids may be selectively delivered to the backing pad 318 and/or the substrate edge 104 via the fluid channels. The controller 206 may be adapted to receive feedback signals from driver(s) and/or actuator(s) that indicate the amount of energy being exerted to drive the substrate 100 (e.g., rotate a vacuum chuck holding the substrate 100) and/or actuate the actuator to push the backing plate 316 and therefore backing pad 318, respectively. These feedback signals may be employed to determine when a particular layer of film 116 has been removed and/or whether a sufficient amount of polishing has occurred.

Turning to FIG. 4, a schematic perspective view of a backing plate 316 according to the present invention is provided. As described above, the driver 302 may cause the substrate support 306 to rotate the substrate 100, as indicated by the directional arrow or in the opposite direction. As the substrate 100 rotates, the backing plate 316 may contact and press the backing pad 318 (and/or polishing tape or a polishing pad) against the substrate edge 104, as indicated by the directional arrow, dotted line of the backing pad and backing plate, thereby creating a particular film profile. In some embodiments the backing pad 318 may conform, or be conformable, to the shape of the backing plate 316, and be affixed thereto. In other embodiments, as shown herein, the backing pad 318 may not conform to the shape of the backing plate 316, per se, but the direction and force of the movement of the backing plate 316 against the backing pad 318 may create the desired film profile in accordance with the shape of the backing plate 316.

Turning to FIG. 5A, a schematic cross sectional view of an exemplary backing plate 316 according to the present invention is depicted. The backing plate 316 may rock in a particular pre-set plane, including between a rocking start angle and an end angle, further described below. The backing plate 316 may have a surface 400 adapted to contact the backing pad 318 (FIG. 3) and/or polishing tape or a polishing pad. In the embodiment shown herein, the backing plate 316 may further include a profiled portion having a first flat region 402 and a second curved region 404. The surface 400 of the curved region 404 of the backing plate 316 adapted to contact the backing pad 318 and/or polishing tape or a polishing pad, may have a spherical shape parallel with the backing plate rocking plane, for example. The curved region 404 may have a radius of R1. The radius (R1) of the backing plate 316 may range from 5 mm to infinity (a flat surface), for example. Other suitable radius values may be used. The radius R1 may be selected to provide process optimization flexibility for polishing different types of films on the substrate 100. A cut-off joint 406 may be positioned at the conjunction of the flat region 402 and the curved region 404. The width of the cut-off joint 406 may range from 0 to 50 mm, for example. Other suitable widths may be used. The width of the cut-off joint may provide another control over the width of the substrate edge 104 being polished.

Turning to FIG. 5B, an illustration of the backing plate 316 shown in FIG. 5A is provided. As is further depicted in FIG. 5B, the shape of the cut-off joint 406, may provide control over the profile of the film 116 on the substrate edge 104. The polishing profile may be the shape created when the film 116 is removed, as further described below. In addition, by choosing rocking start and end angles in combination with the radius R1 of the curved region 404, the width of the substrate edge 104 being polished is controlled. The film 116 may be partially or completely removed as per pre-set profiles from 0 to 50 mm from the substrate outer edge 110, for example. Other suitable removal areas may be used.

As described above, the cut-off joint 406 may be positioned at the conjunction of the flat region 402 and the curved region 404. The curved region 404 may contact the major (or top) surface 102 of the substrate edge 104. As shown herein, the curved region 404 may completely remove the film 116 from that portion of the major surface 102. The flat region 402 may also contact the film 116 on the major surface 102 of the substrate edge 104, but may only partially remove the film 116. The use of the cut-off joint 406 may create a sharp angled profile in the film 116 at the location where the curved region 404 and flat region 402 made contact with the film 116. The shape of the cut-off joint 406 may provide control over the profile of the film edge.

Turning to FIG. 6A, another exemplary embodiment of a backing plate 500 according to the present invention is provided. In the embodiment shown herein, a surface 502 of a backing plate 500 has a smooth spherical shape or profile. Unlike the backing plate 316 of FIG. 5A, the spherical shape of the backing plate 500 shown herein may be perpendicular to the backing plate rocking plane, and may have a radius of R2. The perpendicular orientation may allow a backing pad 318 (and/or polishing tape and/or polishing pad) contact with the backing plate surface 502 at all times during the polishing, for example. The value of R2 may range from 50 mm to 500 mm, for example, depending on the backing plate, polishing tape and/or polishing pad properties. Other suitable values may be used. The smooth curvature change of the surface 502 of the backing plate 500 may also provide for a smooth film profile. By varying the cut-off joint 406 shape from a sharp corner (FIG. 5A) to a smooth curvature change (FIG. 6A), the profile of film 116 may have a sharp or gradually-diminished edge.

The backing plate 316, 500 may be made of a plurality of materials, such as metal and plastic, for example. Other suitable materials may be used. The type of material used to form the backing plate 316, 500 may depend on the type of film 116 being polished. For example, when the film 116 is hard, like silicon nitride, the backing plate 316, 500, may be made of hard materials, such as metal or the like, to improve the polishing efficiency. On the other hand, a soft film 116, such as an amorphous carbon film, for example, may require the use of a backing plate 316, 500 made from plastic materials to prevent damage to the substrate 100. In some embodiments, the backing pad 318 surface may be further covered by a cushion to further lower the local pressure, and increase conformity to the desired film profile.

Turning to FIG. 6B, an illustration of the backing plate 500 shown in FIG. 6A is provided. As shown herein, the surface 502 of the backing plate 500 has a smooth spherical shape. Thus, unlike the sharp angled profile of the film 116 formed with the cut-off joint 406, shown in FIG. 5B, the film 116 profile created with the smooth backing plate 500 is smooth and shows a smooth curvature change and gradually diminished edge.

Turning to FIG. 7, a schematic cross-sectional view of another example embodiment of a backing plate 600 according to the present invention is depicted. The backing plate 600 shown herein may include two cut-off joints 602a, 602b. Other backing plate 600 shapes may be used. As shown herein, a top surface of the backing plate 604 may have a flat region 606, delineated between the cut-off joints 602a and 602b. The flat region 606 may have a length or width ranging from about 0 to 50 mm, for example. Other suitable lengths may be used. A smaller flat region 604 may result in a larger local pressure on the film 116 and substrate edge 104 (FIG. 1). The smaller flat region 604 may also facilitate the alignment of the backing plate 600 (and therefore alignment of a backing pad, polishing tape or polishing pad) with the substrate edge 104. A larger flat region 604 width may result in a more efficient usage of the backing pad 318, polishing tape and/or polishing pad, as a larger surface area may contact the film 116 and substrate edge 104. The different benefits associated with a larger and smaller flat region 604 may provide flexibility in optimizing the process according to targeting particular films and desired film profiles.

Turning to FIG. 8, a flowchart is provided depicting an exemplary method 800 for polishing the substrate edge 104. The appropriate backing plate 316 is selected and attached, or coupled, to the polishing head 314 in step S802. An appropriate backing plate may be the backing plate 316 used to create a particular desired film profile. The rocking start and end angles are selected in step S804. As described above, the rocking start and end angles may indicate a path of movement of the backing pad 316. For example, if the rocking start angle is zero degrees, and the rocking end angle is 15 degrees, the backing plate 316 rocks in a path from zero to 15 degrees as it contacts the film 116. The backing plate 316 contacts and applies a force to the backing pad 318, polishing tape and/or polishing pad in step S806. The backing plate 316 contacts the substrate edge 104 via the backing pad 318, polishing tape and/or polishing pad in step S808 (e.g., while the substrate rotates) to create the particular film 116 profile. The contact may be via a rocking motion, as indicated by the rocking start and end angles. The polishing stops when the pre-set film profile is created in step S810.

It should be understood that the inventive edge polishing apparatus described herein may be employed in apparatuses other than those adapted for bevel and edge polishing and/or removal of films on substrates. Further, as will be apparent to those of ordinary skill in the art, the apparatus describe herein may be employed to polish and/or remove films on an edge of a substrate supported in any orientation (e.g., horizontal, vertical, diagonal, etc).

Further, it should be understood that although only examples of cleaning a round substrate are disclosed, the present invention could be modified to clean substrates having other shapes (e.g., a glass or polymer plate for flat panel displays). Further, although processing of a single substrate by the apparatus is shown above, in some embodiments, the apparatus may process a plurality of substrates concurrently.

The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, other backing plates with other profiles may be used (e.g., elliptical, hexagonal, or other profiles). 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.

Claims

1. An apparatus for polishing a film on an edge of a substrate comprising: a polishing head having:a backing plate adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profile portion adapted to provide a pre-set film profile during polishing of the substrate.

2. The apparatus of claim 1 wherein the profile portion is smooth.

3. The apparatus of claim 2 wherein the profile portion is adapted to provide a gradual curvature to the film profile.

4. The apparatus of claim 1 wherein the profile portion is formed by a flat region and a curved region.

5. The apparatus of claim 4 wherein the flat region and the curved region are conjoined at a cut-off joint.

6. The apparatus of claim 5 wherein the cut-off joint is adapted to provide a sharp and angled film profile.

7. The apparatus of claim 1 wherein the backing plate is adapted to rock about the substrate edge.

8. A system for polishing a film on an edge of a substrate comprising: a substrate support, adapted to support and rotate a substrate;a polishing head having:a backing plate adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profile portion adapted to provide a pre-set film profile during polishing of the substrate; anda controller adapted to operate the movement of the polishing head.

9. The system of claim 8 wherein the profile portion is smooth.

10. The system of claim 9 wherein the profile portion is adapted to provide a gradual curvature to the film profile.

11. The system of claim 8 wherein the profile portion is formed by a flat region and a curved region.

12. The system of claim 11 wherein the flat region and the curved region are conjoined at a cut-off joint.

13. The system of claim 12 wherein the cut-off joint is adapted to provide a sharp and angled film profile.

14. The system of claim 8 wherein the backing plate is adapted to rock about the substrate edge.

15. The system of claim 14 wherein the controller is adapted to control the rocking of the backing plate.

16. The system of claim 15 wherein the backing plate is adapted to rock in a path between a rocking start angle and a rocking end angle.

17. The system of claim 8 further comprising a backing pad adapted to conform to the shape of the backing plate.

18. A method for polishing a film on an edge of a substrate comprising: selecting a rocking start angle and a rocking end angle for a profiled backing plate;contacting a film on an edge of a substrate with the backing plate and a polishing material; androcking the backing plate against the film on the substrate edge during polishing.

19. An apparatus for polishing a film on an edge of a substrate comprising: a backing plate adapted to press polishing material against a film on an edge of a substrate, wherein the backing plate has a profile portion adapted to provide a pre-set film profile during polishing of the substrate.