METHODS AND APPARATUS FOR USING A ROLLING BACKING PAD FOR SUBSTRATE POLISHING

Abstract

An apparatus and method are provided to polish an edge of a substrate. The invention includes a polishing head including a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge. 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 cleaning an edge of a substrate.

BACKGROUND OF THE INVENTION

Substrates are used in semi-conductor device manufacturing. During processing, the edge of the substrate may become dirty which may negatively affect the semi-conductor devices on the substrate. Conventional systems may contact a substrate edge with an abrasive film or tape, as the substrate rotates, to clean the edge. However, the substrate may include a notch in the edge to aide in the proper alignment of the substrate during processing. Conventional systems may not take the notch into account when cleaning the substrate edge, and the impact of the abrasive tape on the rotating substrate may result in damage to the notch. Accordingly improved methods and apparatus for cleaning an edge of a substrate are desired.

SUMMARY OF THE INVENTION

In aspects of the invention, an apparatus is provided for polishing an edge of a substrate. The apparatus comprises a polishing head including a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge. In some other aspects of the invention, a system is provided for polishing an edge of a substrate. The system comprises a substrate support adapted to rotate a substrate; a polishing head including a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge; and a controller adapted to control rotation of the substrate and the polishing head.

In yet other aspects of the invention, a method is provided for polishing an edge of a substrate. The method comprises rotating a substrate and contacting an edge of the substrate with a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge the backing pad.

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, including a notch.

FIG. 2 is a schematic plan view of an example embodiment of an edge cleaning system according to the present invention.

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

FIG. 4 is a perspective view of a backing pad according to the present invention.

FIG. 5 is a schematic illustration of the backing pad according to the present invention.

FIG. 6 is a flowchart depicting an example application of the present invention.

DETAILED DESCRIPTION

The present invention provides improved methods and apparatus for cleaning and/or polishing the edge of a substrate. The edge of a substrate may be polished by application of an abrasive polishing pad or abrasive polishing tape contacting the substrate edge via a polishing pad or head, for example, as the substrate is rotated or otherwise moved (e.g., oscillated). According to the present invention, the width of the polishing or backing pad may be large enough such that the backing pad spans beyond the width of the notch in the substrate edge. This extended width may prevent the backing pad from entering into and/or damaging the notch as the substrate edge is polished.

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′. A notch 116 may be located in the outer edge 110 of the substrate 100 and be used to align/position the substrate 100 during various processing steps (e.g., lithography, deposition, etching, cleaning, etc.). The present invention is adapted to clean and/or polish the outer edge 110 and at least one bevel 112, 114 of a substrate 100 without affecting the notch 116 or 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 schematic plan view of an embodiment of a system 200 for polishing parts of the substrate 100, including the major surfaces 102, 102′ and the substrate edge 104.

The system 200 of FIG. 2 includes three polishing apparatuses 202, each including a polishing head 204. However, any number and type of apparatus 202/heads 204 may be used in any practicable combination. In addition, in such multi-head embodiments, each head 204 may use a differently configured or different type of a polishing tape (e.g., different grits, materials, tensions, pressures, etc.) to contact and polish the substrate edge 104. Any number of heads 204 may be used concurrently, individually, and/or in any sequence. The heads 204 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 polishing tape, pushed by a pad in some embodiments (e.g., as depicted in FIG. 3), to polish different portions of the edge 104 of the substrate 100. In some embodiments, one or more of the heads 204 may be adapted to be oscillated or moved (e.g., 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 so as to polish different portions of the substrate edge 104. In some embodiments, one or more of the heads 204 may be adapted to continuously or intermittently oscillate between the various positions. Alternatively, one or more of the heads 204 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 one or more of the heads 204 oscillate (as described above) as well as rotate circumferentially around the substrate 100. This movement may be under the direction of a programmed or user operated controller 205, further described below. Different heads 204 may be used for different substrates 100 or different types of substrates 100. As described above, the system 200 may further include the controller 205, (e.g., a programmed computer, a programmed processor, a microcontroller, a gate array, a logic circuit, an embedded real time processor, etc.), which may control the driver(s) used to rotate the substrate 100 and/or the actuator(s) used to push a polishing pad(s) (FIG. 3) against the substrate edge 104. Note that the controller 205 may be coupled (e.g., electrically, mechanically, pneumatically, hydraulically, etc.) to each of a plurality of actuators. Likewise, the controller 205 may be adapted to receive feedback signals from one or more drivers and/or actuators, that indicate the amount of energy being exerted to rotate the substrate 100 (e.g., rotate a vacuum chuck holding the substrate 100) and/or actuate the actuator(s) to push the polishing pad(s) against the substrate 100. These feedback signals may be employed to determine when a particular layer of film has been removed and/or whether a sufficient amount of polishing has occurred.

As mentioned above, substrate polishing may be performed using one or more polishing apparatuses 202. In one or more embodiments, a plurality of polishing apparatuses 202 may be employed, in which each polishing apparatus 202 may have similar or different characteristics and/or mechanisms. In the latter case, particular polishing apparatuses 202 may be employed for specific operations. For example, one or more polishing apparatuses 202 may be adapted to perform relatively rough polishing and/or adjustments while another one or more polishing apparatus 202 may be adapted to perform relatively fine polishing and/or adjustments. Polishing apparatuses 202 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 202 may be located in a single chamber or module, as shown herein, or alternatively, one or more polishing apparatuses 202 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 202 in the separate chambers may be used in series or otherwise.

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 the 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, such as the controller 205, for example, which may control the angular displacement, angular velocity, and angular acceleration of the substrate 100.

Additionally, unlike some embodiments which may include one or more drive rollers (not shown) and guide rollers (not shown) that are adapted to rotate the edge 104 of the substrate 100 against the polishing tape 318, described below, an advantage of an embodiment using a vacuum chuck is that the apparatus 300 does not need to contact the substrate edge 104 being polished. Thus, the potential of particles accumulating on drive rollers, used in other embodiments to rotate the substrate, and being re-deposited on the substrate edge 104 is eliminated. The need to clean rollers also is eliminated. Further, the possibility of rollers damaging or scratching the edge is also eliminated. By holding the substrate 100 in a vacuum chuck, high speed rotation without significant vibration may be achieved.

The polishing apparatus 300 may further include a polishing arm 310 aligned in the horizontal plane approximately tangential to an edge of the substrate 100, and supported by a frame 312. The frame 312 may be coupled at one end to a polishing head driver 309. 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 or polishing pad 316 and/or inflatable pad. In either case, the pad 316 and/or inflatable pad may be soft and/or include or develop contours to conform to the shape of the substrate edge 104. The polishing pad 316 may be wheel-shaped, as shown herein, for example. Other shapes may be used. The polishing pad 316 may be moved towards or away from the substrate 100 by an actuator (e.g., hydraulic actuator, pneumatic actuator, servomotor, etc.) (not shown). The actuator may be under the control of the controller 205, for example. The actuator may rock the head 314 between a desired angle, including for example ±90 degrees, thereby contacting the entire edge 104 of the substrate 100 with the polishing tape 318. Other angles may be used. In operation, this is achieved by angularly translating the head 314 and consequently, a portion of polishing tape 318 in contact with and contoured to the substrate edge 104, around an axis that is tangential to the outer edge 110 of the substrate 100 as it is rotated. Alternatively, a biasing device (e.g., a spring) may be employed to mount the polishing pad 316 to the head 314 to provide flexible/dynamic counter pressure to the polishing pad 316. Polishing tape 318, may wrap around the polishing head 314, and guide rollers 320, 322 and over the polishing pad 316, and be tensioned between spools 324, 326. The spools 324, 326 may be driven by spool drivers 328, 330 (e.g., servomotors), respectively. The spool drivers 328, 330, may be moved continuously or indexed to precisely control the amount of the polishing tape 318 that is advanced over the polishing head 314 from, for example, the spools 324, 326, in order to polish the substrate edge 104. The substrate 100 may contact the abrasive tape 318 for 15 to 150 seconds depending on the type of tape 318 used, the grit of the tape, the rate of rotation, the amount of polishing required, etc. More or less time may be used.

Depending on the amount of force applied by the actuator, the resiliency of the pad selected, the amount of inflation of an inflatable pad, and/or the amount of tension on the tape, a controlled amount of pressure may be applied to polish the edge 104. Thus, the present invention provides precise control of an edge polish process, which may be used to compensate for different edge geometries and changes in the substrate 100 as material is removed from the edge 104.

In one or more embodiments, the polishing tape 318 may be made from 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, for example, from about 0.5 microns up to about 3 microns in size or 0.1 microns to 10 microns in size, although other sizes may be used. Different widths of polishing tape 318 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 318 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 324, 326 may have a diameter of approximately 1 inch and be capable of holding about 500 inches of polishing tape 318, for example, or may have a diameter of approximately 3 inches and be capable of holding about 30,000 inches of polishing tape 318, for example. Other spool dimensions may be used. The spools 324, 326 may be constructed from materials such as nylon, polyurethane, polyvinyl difluoride (PVDF), etc. Other materials may also be used.

The polishing pad 316 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 materials may be used. Such materials may have a resilience or an ability to conform that is a function of the thickness or density of the polishing pad. The material may be selected based upon its resilience. The material may be selected based upon other qualities. The desired resilience may be selected based upon the type of polishing required. The desired resilience may be selected based upon other criteria.

In some embodiments, fluids used to aid in the polishing or washing away of accumulated particles, may be delivered to the substrate edge 104. The chemicals may be sprayed directly onto the substrate 100, at the substrate/abrasive tape interface, and/or may be applied to and/or through the tape and/or the polishing pad 316. A fluid channel may be provided to drip or spray the fluid on or into the polishing pads 316. Alternatively, an inflatable pad may include a bladder with a semi-permeable membrane that allows fluid to be slowly released and transmitted to the abrasive tape (e.g., through the pad). In such embodiments, the pad 316 may be covered by, made of, and/or include material that absorbs and/or retains the fluids used (e.g., polyvinyl alcohol (PVA), etc.). Additionally, 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.

The substrate 100 may be rotated in a horizontal plane. The edge 104 of the substrate 100 may be aligned with or normal to the polishing tape 318, polishing pad 316 and/or polishing head 314. In additional or alternative embodiments, the substrate 100 may be rotated in a vertical plane, other non-horizontal plane, and/or be moved between different planes of rotation.

Turning to FIG. 4, the present invention provides an exemplary backing pad 400 for use with an abrasive polishing film or tape 500, shown in FIG. 5, to clean the edge 104 of the substrate 100. In the embodiment shown herein, the backing pad 400 is contoured in a concave shape forming essentially a concave cylinder. Other shapes may be used. In some embodiments, the backing pad 400 may have a radius of approximately 150 mm, for example. Other suitable radii may be used. The backing pad 400 may be designed to be wide enough that it spans beyond the width of the notch 116 as it polishes the substrate edge 104, as shown in FIG. 5. This may ensure that the backing pad 400 does not “fall” or enter into the notch 116 during polishing, and cause damage to the notch 116 or edge 104 of the substrate 100 as a result of the impact. Additionally, to further prevent damage to the substrate 100, the backing pad 400 may be made from a soft material, for example, with less than Shore A 70 durometer, such as polueurethene 70 which has a hardness of Shore A 60 durometer. Other degrees of softness may be used. The softness of the backing pad material may also permit compression of the backing pad 400, which may aid in polishing the bevels 112, 114 of the substrate 100.

The backing pad 400 may be hollow or may include a bore therethrough, which may permit the backing pad 400 to be mounted on a cylindrical roller 402. Other roller shapes may be used. The backing pad 400 and the roller 402 may be positioned in the polishing head 314, shown in FIG. 3. When the roller 402 is positioned in the polishing head 314, a clearance of 0.5 mm, for example, on each side of the roller 402 adjacent the backing pad 400 may be included to allow for adjustments in case of errors in the alignment of the notch 116 with the backing pad 400. Other measurements providing sufficient clearance may be used.

Turning to FIG. 5, a schematic illustration of the backing pad 400 shown in FIG. 4 is provided. In operation, the backing pad 400, pushed by an actuator (not shown), may press the polishing tape 500 (only a portion shown in cross-section) against the substrate edge 104 to polish the substrate edge 104. Both the backing pad 400 and the roller 402 may be able to rotate freely with the polishing tape 500, to aid the polishing tape 500 in polishing the edge 104. In other words, the rotation of the backing pad 400 with the polishing tape 500 may create less friction therebetween than with a non-rotating backing pad, for example, which may drag the polishing tape 500. The decreased friction may result in less wear and tear on the polishing tape 500, for example, thereby increasing the usable life of the polishing tape 500. Additionally, the decreased friction may result in a decrease of particle formation. Particle formation may be undesirable due to its ability to interfere with the polishing system components and substrate production.

In some embodiments, as described above, the backing pad 400 may be concave. In such embodiments, the radius of curvature of the concavity may be selected to match the curvature of the circumference of the substrate 104 to be polished. Thus, for example, for a 300 mm substrate, the radius of curvature of the concavity may be approximately 150 mm, for a 200 mm substrate, the radius of curvature of the concavity may be approximately 100 mm, and for a 400 mm substrate, the radius of curvature of the concavity may be approximately 200 mm. Other radii of curvature may be used for these various example sizes of substrates. For example, a radius of curvature that is slightly larger than the radius of curvature of the substrate may be selected to account for the polishing tape 500 and/or allow the notch 116 to move past the backing pad 116 more easily (e.g., without catching an edge of the polishing tape). In some embodiments, the ends of the backing pad 400 may be rounded as depicted in FIG. 5. By having the ends of the backing pad 400 rounded, the notch 116 may more easily pass by the backing pad 400. In addition, the edges of the polishing tape 500 may conform to the rounded ends of the backing pad 400 so that the notch 116 has less of an opportunity to catch an edge of the polishing tape 500 as the notch 116 passes the backing pad 400.

The entire substrate 100 may be rotated as the polishing tape 500 is pressed against the substrate edge 104, such that the entire circumference of the substrate edge 104 is polished.

As described above, the backing pad 400 may be wide enough to span beyond the notch 116 and polish the substrate edge 104 as well. If the backing pad 400 was too narrow, when the backing pad 400 contacts the notch 116 as the substrate 100 rotates, the backing pad 400 may “fall” into or contact the notch 116 at an angle, and may damage the sides of the notch 116. Additionally, if the backing pad 400 were to “fall” entirely within the notch 116, the backing pad 400 may damage the notch 116 as the backing pad 400 is moved out of the notch 116 as the substrate 100 rotates.

Turning to FIG. 6, an exemplary method 600 for polishing the edge of a substrate is provided. In step S102, the substrate 100 is rotated. In step S104, the backing pad 400 presses the polishing tape 500 against the substrate edge 104. In step S106, the polishing head 314 (and consequently the backing pad 400) rocks about the substrate edge 104. In step S108, the polishing tape 500 is advanced. As described above, the polishing tape 500 may be advanced continuously or in increments. In step S110 the backing pad is rotated about the roller 402. As described above, the rotation of the backing pad 400 with the polishing tape 500 may create less friction therebetween than with a non-rotating backing pad, for example, which may drag the polishing tape 500. The decreased friction may result in less wear and tear on the polishing tape 500, for example, thereby increasing the usable life of the polishing tape 500. Additionally, the decreased friction may result in a decrease of particle formation, as particle formation may be undesirable due to its ability to interfere with the polishing system components and substrate production. In step S112, it is determined whether a pre-set amount of film has been removed from the substrate edge. As described above, the controller 205 may receive feedback signals from the driver and/or actuator. The feedback signals may be used to determine when a particular layer of film has been removed and/or whether a sufficient amount of polishing has occurred.

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. 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 an edge of a substrate comprising: a polishing head including a backing pad, wherein a width of the backing pad that contacts a substrate edge is larger than a width of a notch in the substrate edge.

2. The apparatus of claim 1 wherein the backing pad is cylindrically shaped.

3. The apparatus of claim 2 wherein the backing pad includes a bore therethrough.

4. The apparatus of claim 3 further comprising a roller.

5. The apparatus of claim 4 wherein the backing pad is mounted on the roller via the bore.

6. The apparatus of claim 5 wherein the backing pad is adapted to rotate about the roller.

7. The apparatus of claim 1, wherein the backing pad is adapted to conform to the substrate edge.

8. The apparatus of claim 1 wherein the polishing head is adapted to rock about the substrate edge.

9. The apparatus of claim 1 wherein the backing pad is adapted to press a polishing tape against the substrate edge.

10. A system for polishing an edge of a substrate comprising: a substrate support adapted to rotate a substrate;a polishing head including a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge; anda controller adapted to operate the rotation of the substrate and the polishing head.

11. The system of claim 10 wherein the backing pad is cylindrically shaped.

12. The system of claim 11 wherein the backing pad includes a bore therethrough.

13. The system of claim 12 further comprising a roller.

14. The system of claim 13 wherein the backing pad is mounted on the roller via the bore.

15. The system of claim 10, wherein the backing pad is adapted to conform to the substrate edge.

16. The system of claim 10 wherein the polishing head is adapted to rock about the substrate edge.

17. The system of claim 10 wherein the backing pad is adapted to press a polishing tape against the substrate edge.

18. A method for polishing an edge of a substrate comprising: rotating a substrate; andcontacting an edge of the substrate with a backing pad, wherein a width of the backing pad that contacts the substrate edge is larger than a width of a notch in the substrate edge the backing pad.

19. The method of claim 18 further comprising: pressing a polishing tape against the substrate edge with the backing pad.

20. The method of claim 19 further comprising: advancing the polishing tape in increments.

21. The method of claim 19 further comprising: advancing the polishing tape continuously.

22. The method of claim 18 wherein the polishing pad is coupled to a polishing head.

23. The method of claim 22 further comprising: rocking the polishing head about the edge of the substrate.

24. The method of claim 18 further comprising: rotating the backing pad about a roller.

25. The method of claim 18 further comprising: determining that a pre-set amount of film has been removed from the substrate edge.