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Publication numberUS20030013397 A1
Publication typeApplication
Application numberUS 09/892,321
Publication dateJan 16, 2003
Filing dateJun 27, 2001
Priority dateJun 27, 2001
Publication number09892321, 892321, US 2003/0013397 A1, US 2003/013397 A1, US 20030013397 A1, US 20030013397A1, US 2003013397 A1, US 2003013397A1, US-A1-20030013397, US-A1-2003013397, US2003/0013397A1, US2003/013397A1, US20030013397 A1, US20030013397A1, US2003013397 A1, US2003013397A1
InventorsRobert Rhoades
Original AssigneeRhoades Robert L.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Polishing pad of polymer coating
US 20030013397 A1
Abstract
A polishing pad constructed with an underlay providing a shaped preform, and a layer of polishing material provided as a coating conforming to the shaped preform, the coating forming a polishing surface on the polishing pad, the coating adhering to the shaped preform without completely covering openings extending through the thickness of the underlay, whereby the openings provide the polishing pad with a desired porosity.
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Claims(34)
What is claimed is:
1. A polishing pad comprising: an underlay with openings extending through the thickness of the underlay, the underlay providing a shaped preform, and a layer of polishing material provided as a coating conforming to the shaped preform, the coating forming a polishing surface on the polishing pad, the coating adhering to the shaped preform without completely covering the openings extending through the thickness of the underlay, whereby the openings provide the polishing pad with a desired porosity.
2. The polishing pad as recited in claim 1, further comprising: the openings providing passages for flowing polishing fluid.
3. The polishing pad as recited in claim 1, further comprising: the openings being arranged in an array of openings, and the array of openings through the thickness of the underlay providing a porous filter.
4. The polishing pad as recited in claim 1, further comprising: the shaped preform having a preform topography corresponding to a desired surface texture for the polishing pad, and the coating conforming to the preform topography to provide the polishing pad with the desired surface texture.
5. The polishing pad as recited in claim 1, further comprising: the shaped preform having reinforcing strands.
6. The polishing pad as recited in claim 1, further comprising: the shaped preform being a further polishing material under the coating of polishing material.
7. The polishing pad as recited in claim 1, further comprising: the coating further having abrasive particles distributed in the polishing material.
8. The polishing pad as recited in claim 1, further comprising: the underlay having multiple strands arranged in an array of strands, and the openings through the thickness of the underlay being provided by clearance spaces among the strands.
9. The polishing pad as recited in claim 1, further comprising: the underlay having multiple strands arranged in an array of strands, the array of strands including one or more of; an randomly arranged array, a woven array, and a repeating pattern array, and the openings through the thickness of the underlay being provided by clearance spaces among the strands.
10. The polishing pad as recited in claim 1, further comprising: the underlay having multiple strands arranged in an array of strands, the array of strands including, a woven array and a repeating pattern array, and the openings through the thickness of the underlay being provided by clearance spaces among the strands.
11. A polishing pad comprising: an underlay providing a shaped preform, the shaped preform having a shaped preform topography corresponding to a desired surface texture for the polishing pad, and a layer of polishing material provided as a coating conforming to the shaped preform, the coating forming a polishing surface on the polishing pad, and the coating overlying the shaped preform topography to provide the polishing surface with a surface texture with minimized macro-defects.
12. The polishing pad as recited in claim 11, further comprising: openings extending through a thickness of the underlay, the coating adhering to the underlay without covering the openings, and the openings providing the polishing pad with a desired porosity.
13. The polishing pad as recited in claim 11 wherein, the shaped preform comprises, multiple strands arranged in an array of strands, the shaped preform topography being shaped by sizes and shapes of the strands.
14. The polishing pad as recited in claim 1 wherein, the shaped preform comprises, multiple strands woven together, the polishing material comprises, a coating on each of the strands, and the coating on each of the strands being woven together with the strands.
15. The polishing pad as recited in claim 1 wherein, the shaped preform comprises, multiple strands woven together, the polishing material comprises, a coating on each of the strands, and the strands being woven together without the coating being woven together with the strands.
16. A method for making a polishing pad, comprising the steps of: fabricating an underlay to provide a preform with a shaped preform topography corresponding to a desired surface texture for the polishing pad, overlying the underlay with a polishing material in a manner to provide a polishing surface on the polishing pad, and overlying the shaped preform topography with the polishing material to provide the polishing surface with a surface texture with minimized macro-defects.
17. The method as recited in claim 16, further comprising: providing openings through the underlay to provide passages for flowing polishing fluid.
18. The method as recited in claim 16, further comprising: providing openings through the underlay to provide passages of a porous filter.
19. The method as recited in claim 16, further comprising: providing the underlay with reinforcing strands.
20. The method as recited in claim 16, further comprising: providing the shaped preform as having a further polishing material under the coating of polishing material.
21. The method as recited in claim 16, further comprising: providing the coating with abrasive particles distributed in the polishing material.
22. The method as recited in claim 16, further comprising: providing the underlay as having multiple strands arranged in an array of strands, and providing openings through the thickness of the underlay as clearance spaces among the strands.
23. The method as recited in claim 16, further comprising: providing the underlay as having multiple strands arranged in an array of strands, the array of strands including one or more of; an randomly arranged array, a woven array, and a repeating pattern array, and providing openings through the thickness of the underlay as clearance spaces among the strands.
24. The method as recited in claim 25, further comprising: providing the underlay as having multiple strands arranged in an array of strands, the array of strands including, a woven array and a repeating pattern array, and providing openings through the thickness of the underlay as clearance spaces among the strands.
25. A method for making a polishing pad, comprising the steps of: fabricating an underlay as a shaped preform with openings extending through the thickness of the underlay, coating the underlay with a layer of polishing material in a manner to conform the coating to the shaped preform and form a polishing surface on the polishing pad, and adhering the coating to the shaped preform without completely covering the openings extending through the thickness of the underlay to provide the polishing pad with a desired porosity.
26. The method as recited in claim 25, further comprising: providing openings through the underlay to provide passages for flowing polishing fluid.
27. The method as recited in claim 25, further comprising: providing openings through the underlay to provide passages of a porous filter.
28. The method as recited in claim 25, further comprising: providing the shaped preform with a preform topography corresponding to a desired surface texture for the polishing pad, and conforming the coating to the preform topography to provide the polishing pad with the desired surface texture.
29. The method as recited in claim 25, further comprising: providing the underlay with reinforcing strands.
30. The method as recited in claim 25, further comprising: providing the shaped preform as having a further polishing material under the coating of polishing material.
31. The method as recited in claim 25, further comprising: providing the coating with abrasive particles distributed in the polishing material.
32. The method as recited in claim 25, further comprising: providing the underlay as having multiple strands arranged in an array of strands, and providing the openings through the thickness of the underlay as clearance spaces among the strands.
33. The method as recited in claim 25, further comprising: providing the underlay as having multiple strands arranged in an array of strands, the array of strands including one or more of; an randomly arranged array, a woven array, and a repeating pattern array, and providing the openings through the thickness of the underlay as clearance spaces among the strands.
34. The method as recited in claim 25, further comprising: providing the underlay as having multiple strands arranged in an array of strands, the array of strands including, a woven array and a repeating pattern array, and providing the openings through the thickness of the underlay as clearance spaces among the strands.
Description
    BACKGROUND OF THE INVENTION
  • [0001]
    1. Field of the Invention
  • [0002]
    The present invention relates to polishing pads for polishing dielectric/metal composites, semiconductors, integrated circuits and metal underlays.
  • [0003]
    2. Discussion of Related Art
  • [0004]
    Polishing is a manufacturing process performed by a polishing pad rubbing against a surface of an article to be polished, while a polishing fluid comprising a chemical solution, sometimes containing a suspension of fine particles, typically a slurry, is present at the interface between the polishing pad and the work piece. A polishing material that is suitable for a polishing surface of a polishing pad, comprises, for example, polyurethanes, polyesters, polystyrenes, polyimides, felts impregnated with a polyesters or urethanes, and various combinations or composites of such materials.
  • [0005]
    U.S. Pat. No. 5,489,233, to Cook et al., discloses that polishing pads are provided with a surface texture. The surface texture transports polishing fluid over the surface of the polishing pad, to assure that a sufficient quantity of polishing fluid is retained between the surface of the polishing pad and the workpiece being polished, which overcomes a tendency for the polishing fluid to be expelled when the polishing pad and the workpiece are in contact with each other. The surface texture is provided on the polishing pad by a manufacturing process, such as; embossing, pressing, casting, or by cutting with sharp abrasive devices.
  • [0006]
    As disclosed by U.S. Pat. No. 6,022,268, to Roberts et al., the same manufacturing process that forms a surface texture on a polishing pad, further, forms macro-defects that become included in the surface texture. Such macro-defects comprise undesired protrusions, including burrs, about 25 microns or greater in size. Inherent variables in the manufacturing process cause macro-defects that differ in size and in numbers on respective polishing pads. Accordingly, the polishing pads that are subjected to the same manufacturing process have different surface textures that will polish with, either a faster polishing rate, or a slower polishing rate, when used in a polishing operation. The polishing operation is automated to polish a workpiece for a limited time duration that is fixed, according to an expected, consistent polishing rate of the pads. However, the pads that polish at different polishing rates will produce undesired, different polishing results within such a time duration. Thus, a manufacturing process is desired that will provide a polishing pad with a surface texture having minimized macro-defects, which promotes a consistent surface texture and, in turn, a consistent polishing rate.
  • [0007]
    Some polishing operations use a polishing apparatus of a type that requires a polishing pad to have openings of small circumference through the thickness of the pad. Such openings, for example, provide passages to dispense polishing fluid or to transmit an emanating optical beam transmitted by an optical monitoring apparatus. The openings are provided by a manufacturing operation, such as, subjecting a polishing pad to drilling or punching, which provides undesired further burrs (further macro-defects) in the surface texture on the polishing pad. It would be desirable to provide a polishing pad with passages without further providing macro-defects, such that the polishing pad has a surface texture having minimized macro-defects, which promotes a consistent surface texture and, in turn, a consistent polishing rate.
  • SUMMARY OF THE INVENTION
  • [0008]
    The invention resides in a polishing pad having, an underlay that provides a preform with a shaped preform topography corresponding to a desired surface texture for the polishing pad, and a polishing material overlying the underlay to provide a polishing surface on the polishing pad, the polishing material overlying the shaped preform topography to provide the polishing surface with a surface texture with minimized macro-defects.
  • [0009]
    The invention further resides in a method for making a polishing pad by the steps of, fabricating an underlay to provide a preform with a shaped preform topography corresponding to a desired surface texture for the polishing pad, overlying the underlay with a polishing material in a manner to provide a polishing surface on the polishing pad, and overlying the shaped preform topography with the polishing material to provide the polishing surface with a surface texture with minimized macro-defects.
  • [0010]
    The invention further resides in a polishing pad having, an underlay with openings extending through the thickness of the underlay, the underlay providing a shaped preform, and a layer of polishing material provided as a coating conforming to the shaped preform, the coating forming a polishing surface on the polishing pad, the coating adhering to the shaped preform without completely covering the openings extending through the thickness of the underlay, and the openings providing the polishing pad with a desired porosity.
  • [0011]
    The invention further resides in a method for making a polishing pad by the steps of, fabricating an underlay as a shaped preform with openings extending through the thickness of the underlay, coating the underlay with a layer of polishing material in a manner to conform the coating to the shaped preform and form a polishing surface on the polishing pad, and adhering the coating to the shaped preform without completely covering the openings extending through the thickness of the underlay to provide the polishing pad with a desired porosity.
  • [0012]
    Embodiments of the invention will now be described, by way of example, with reference to the following detailed description taken in conjunction with accompanying drawings that are described as follows.
  • DESCRIPTION OF THE DRAWINGS
  • [0013]
    [0013]FIG. 1 is top view of a portion of a polishing pad.
  • [0014]
    [0014]FIG. 2 is a cross section of the polishing pad portion of FIG. 1 taken along line 22.
  • [0015]
    [0015]FIG. 2A is a cross section of an embodiment of a strand.
  • [0016]
    [0016]FIG. 2B is a cross section of another embodiment of a strand.
  • [0017]
    [0017]FIG. 2C is a cross section of another embodiment of a strand.
  • [0018]
    [0018]FIG. 3 is a cross-section of an embodiment of a reinforcing strand.
  • [0019]
    [0019]FIG. 3A is a cross section of another embodiment of a strand having a reinforcing strand at its core.
  • DETAILED DESCRIPTION
  • [0020]
    [0020]FIG. 1 discloses an embodiment of a polishing pad 10 provided with an underlay 12 having multiple strands 1 in an arranged array of strands 1. For example, the strands 1 are provided in the underlay 12 as a fabric of a woven array of threads, the threads being an exemplary embodiment of strands 1. Another embodiment of strands 1 comprise fibers of the types, as disclosed by U.S. Pat. No. 4,728,552 to Jensen, and as disclosed by U.S. Pat. No. 4,927,432, to Budinger et al.
  • [0021]
    An arranged array of strands 1 is constructed by arranging multiple strands 1 according to one type of arranged array, or a combination of more than one type of arranged array. The types of arranged arrays include, but are not limited to; a random array, a woven array, as disclosed by FIG. 1, and a repeating pattern array. FIG. 1 discloses a single type of arranged array that is representative of an embodiment of a woven array of strands 1, and that is further representative of an embodiment of a repeating pattern array of strands 1. Another embodiment of a repeating pattern array of strands 1 includes, but is not limited to, strands 1 of various sizes that are arranged in a repeating pattern of such sizes. Another embodiment of a repeating array of strands 1 includes, but is not limited to, strands 1 of various shapes that are arranged in a repeating pattern of such shapes. Another embodiment of a repeating pattern array of strands 1 includes, but is not limited to, strands 1 made of different materials that are arranged in a repeating pattern of such materials.
  • [0022]
    An embodiment of a random array of strands 1 includes, but is not limited to, a group of multiple strands 1 extending in random directions. The group includes, but is not limited to, a bundle of strands 1, a nonwoven mat of multiple strands 1, and a stack of strands 1 that are not in a bundle or in a mat. Although the arranged array disclosed by FIG. 1 comprises a single type of arranged array, the invention includes one, or more than one of the different types of arranged arrays in the same underlay 12.
  • [0023]
    With further reference to FIG. 1, there are openings 2 through the underlay 12 providing both underlay 12, and the resulting polishing pad 10 with porosity. The openings 2 are provided by clearance spaces among the multiple strands 1 in the arranged array of strands 1. For example, the clearance spaces are bounded by portions of adjacent strands 1 in the arranged array. Although FIG. 1 discloses a single layer of strands 1, the underlay 12 can have multiple layers of strands 1, one on another, which provides openings 2 that extend from one layer to another, even if the openings 2 in one layer are offset aligned with the openings 2 in another layer.
  • [0024]
    Accordingly, an array of openings 2 through the thickness of the underlay 12 are provided by an array of clearance spaces among the strands 1 in the array of strands 1. A selection of a dense array of strands 1, wherein the strands are spaced relatively close to one another, provides smaller clearance spaces, as compared to a selection of a less dense array of strands 1, wherein the strands 1 are spaced relatively farther apart from one another, provides larger clearance spaces. Such a selection of the density of the strands 1 comprises an embodiment of a process step in the process of selecting the sizes of the openings 2 to correspond with the desired amount of porosity of the underlay 12.
  • [0025]
    According to an embodiment, openings 2 in the range of 0.01-10 microns, more preferably, about 0.10-5.0 microns extend through a thickness of about 10-1,000 microns. Typically, the number of openings 2 per square cm that are in the underlay 12 and the pad 10 is about 5-1000 openings 2 per square cm. In an embodiment, the underlay 12 has a thickness of less than 250 microns, more preferably about 50-150 microns.
  • [0026]
    A selection of relatively wider strands 1 or relatively larger sized strands 1 in the array of strands 1 locate clearance spaces between such strands 1 that are spread farther apart from one another, as compared to a selection of narrower strands 1 or smaller sized strands 1 in the array that locate the clearance spaces relatively closer together. Such a selection of the sizes of the strands 1 comprises an embodiment of a process of selecting the number and density of clearance spaces resulting in the openings 2 that populate the underlay 12, which correspond to a desired porosity of the underlay 1. For example, the openings 2 provide passages for flowing polishing fluid, or provide passages for transmission of an optical beam being transmitted by an optical monitoring apparatus, for example, an apparatus as described in U.S. Pat. No. 6,045,439. Further, for example, the openings 2 are sized to provide the polishing pad 10 as a porous filter. The polishing pad 10 filters particles from a polishing fluid that circulates through the polishing pad 10. The polishing fluid is pumped from the rear of the polishing pad 10 and through the openings 2. Particles of contaminants larger than the openings 2 are effectively filtered out and do not reach the surface of the polishing pad 10 where they could scratch or gouge the surface of an article being polished.
  • [0027]
    With further reference to FIG. 1, the underlay 12 provides a shaped preform for polishing material in the form of a coating 3 that is applied to overlie the shaped preform, and to conform to the shaped preform and provide a polishing surface on the polishing pad 10. The polishing material is selected from polymers that are suitable for polishing workpieces comprising semiconductor wafers. Such suitable polymers are disclosed, for example, by U.S. Pat. Nos. 6,022,268 and U.S. 6,036,579 and U.S. 6,095,902, incorporated by reference herein. The coating 3 is applied as a fluid phase polymer to overlie the shaped preform, by performing a coating process, for example, by spraying, agglomerating, or applying with an applicator, such as, a roller or a brush or doctor blade. After the coating 3 is applied over the underlay 12, it is cured to a solid phase polymer by air drying, heating or irradiation as required by how different types of polymers become solidified. The fluid phase polymer forms a coating adhered to the strands 1. Especially when the strands 1 are arranged in a group without restraint, the coating of solid phase adheres to adjacent strands 1, and joins such strands 1 to retain them in their arranged positions within the polishing pad 10. The strands 1 are prevented from shifting from their arranged positions within the polishing pad 10.
  • [0028]
    According to an embodiment, when the fluid phase polymer has a relatively high viscosity, a thin coating 3 of the polishing material is applied on the surface of the shaped preform, while carefully avoiding the openings 2. The polishing material adheres to the shaped preform without flowing into the openings 2, which avoids completely covering the openings 2, whereby the openings 2 provide the desired porosity of both the underlay and the polishing pad 10. According to another embodiment, when the fluid phase polymer has a relatively low viscosity, a thin coating 3 of the polishing material is applied on the surface of the shaped preform. The fluid phase polymer lacks stiffness, and is unable to bridge across the openings 2 and is unable to completely cover the openings 2, whereby the openings 2 provide the desired porosity of both the underlay and the polishing pad 10.
  • [0029]
    [0029]FIG. 1 discloses an embodiment of a polishing pad 10 that is manufactured according to alternate processes. According to an embodiment of the process, the coating 3 is applied to the strands 1 after the strands 1 have been arranged in an array of strands 1, for example, a woven array. According to another embodiment of the process, the coating 3 is applied to each of the strands 1 to provide coated strands 1, followed by arranging an array of coated strands 1, in an array of strands 1, for example, a woven array. The coating 3 is arranged in the array together with the strands 1 that are coated with the coating 3. For example, the coating 3 on each of the strands 1 is woven together with the strands 1.
  • [0030]
    According to an embodiment, the coating 3 is applied to each of the strands 1 by extruding a fluid phase polymer material concentrically over each strand 1 to provide coated strands 1, followed by arranging the coated strands 1 in an arranged array, for example, the woven array disclosed by FIG. 1. The polymer is cured to a solid phase polymer that provides the polishing surface on the polishing pad 10.
  • [0031]
    According to an embodiment of desired porosity, the openings 2 through the coating 3 and through the polishing surface of the polishing pad are sufficiently large to provide passages for flowing polishing fluid, or passages for transmitting vacuum or air pressure, or for transmitting an optical beam of an optical monitoring device. According to another embodiment of desired porosity, the openings 2 are sufficiently small and comprise a distributed population throughout the pad 10 to provide a porous filter that allows passage of vacuum or air pressure or polishing fluid through the openings 2, and that filters out particles of contaminants that are too large for passage through the openings 2. By selecting the arrangement of the strands 1, a combination of openings 2 of different sizes are provided in the same polishing pad 10.
  • [0032]
    When the coating 3 of polishing material overlies the preform topography, the coating 3 of polishing material becomes shaped, and is provided with a surface texture resulting by its conformance to the preform topography that includes a shape and surface texture. Accordingly, the preform topography is selected with a construction, including its shape and its surface texture, to correspond to the desired surface topography, including shape and surface texture, of the polishing surface when the polishing material forms a distributed coating 3 conforming to the shape and surface texture on the preform topography.
  • [0033]
    The underlay 12 provides the preform with a preform topography as determined by the selection of the strands 1 and the selection of the arrangement of the strands 1.
  • [0034]
    The coating 3 of polishing material overlies the preform topography to provide a desired surface texture for the polishing pad 10. Accordingly, the preform has a shaped preform topography that is selected to correspond with such a desired surface texture for the polishing pad 10. The coating 3 covers any macro-defects present on the preform topography, and buries such macro-defects in the coating 3. Further, the coating 3 shrinks slightly upon curing to smooth the surface thereof, which minimizes macro-defects on the surface, such that the coating 3 provides a polishing surface with minimized micro-defects. The surface texture of the polishing surface is determined by the selected peaks and valleys of the preform topography and the macro-defect free surface of the coating 3 conforming to the peaks and valleys.
  • [0035]
    The strands 1 that are present in the array of strands 1 have exterior surfaces that are selected so as to shape the preform topography, and so as to provide the shaped preform topography with a surface texture comprised of peaks and valleys. For example, FIG. 2 discloses an embodiment wherein the strands 1 have curved exterior surfaces 1 a. Further, the curved exterior surfaces 1 a are cylindrical. FIG. 2A discloses another embodiment of a strand 1 having a curved exterior surface 1 b that contributes to the shape of the preform topography. FIG. 2A discloses that an exterior surface 1 b that contributes to the shape of the preform topography is not required to be continuous over the entire perimeter of the strand 1. FIG. 2B discloses an embodiment of a strand 1 having a flat exterior surface 1 c that contributes to the shape of the preform topography. FIG. 2C discloses an embodiment of a strand 1 having an undulated exterior surface id that contributes to the shape of the preform topography. Although FIG. 1 discloses an underlay having multiple strands that are identical, the invention is meant to include an underlay that is constructed of any combination of strands that are either identical or not identical.
  • [0036]
    The strands that are present in the array of strands have sizes that are selected so as to shape the preform topography, and so as to provide the preform topography with a surface texture comprised of peaks and valleys. For example, FIG. 2 discloses strands that have uniform sizes. FIG. 2A discloses an embodiment of a strand having a cross section that is wider than it is tall, which provides an embodiment of a strand having cross section that is not the same size as the cross sections of the cylindrical strands disclosed by FIG. 2. The tallest portion of the cross section provides a peak in the preform topography. The lower height portion of the cross section beside the peak provides a valley in the preform topography. FIG. 2B discloses an embodiment of a strand having a cross section that is taller than it is wide, which provides an embodiment of a strand having a cross section that is not the same size as the cross section of any one of the strands disclosed by FIG. 2 and FIG. 2A. Further, FIG. 2C discloses an embodiment of a strand having cross section that is not the same size as the cross section of any one of the strands disclosed by FIGS. 2, 2A and 2B. Accordingly, the sizes of the strands contributes to the shape of the preform topography. The strand 1 disclosed by FIG. 2C has an undulated surface 1 d that provides undulated peaks and valleys in the preform topography. Although two undulations are disclosed, the number of undulations is a matter of selection to attain a corresponding benefit of the preform topography according to the invention.
  • [0037]
    According to a embodiment, the coating 3 is without abrasive particles in the polishing material to provide an abrasive free polishing pad 10. According another embodiment, the coating 3 is further provided with distributed abrasive particles in the polishing material to provide an abrasive polishing pad 10. The abrasive particles are of submicron size, and are present in one range of size distributions or more than one range of size distributions. For example, abrasive particles can be incorporated into the polymeric polishing layer in amounts of about 0.1-75% by weight, based on the weight of the polymeric polishing layer. The abrasive particles have a mean size range of 10-500 nm or a mixture of primary particles and agglomerated smaller particles having a mean size range of 25-500 nm. Typically useful abrasive particles are alumina, silica, titania, ceria and the like.
  • [0038]
    Polishing is performed with the polishing pad 10 and a polishing fluid. The polishing fluid comprises an embodiment that contains abrasives, or alternatively, an embodiment that is abrasive free. The polishing fluid may contain oxidizers, pH buffing agents, organic additives and the like that provide chemical reactions with the material compositions on a surface of the article being polished.
  • [0039]
    According to another embodiment, FIG. 3 is an enlarged cross section of a reinforcing strand 1 e. One or more than one reinforcing strands 1 e are arranged with other strands 1 in a corresponding array of strands 1 and 1 e. According to an embodiment, each reinforcing strand 1 e is smaller in cross section, or size, than the strands 1 in an array of strands 1 and 1 e, such that each of the strands 1 e is recessed in the array of strands 1 and 1 e, and is recessed below the polishing surface formed by the coating 3 applied to the strands 1. The coating 3 is further applied to each of the recessed strands 1 e.
  • [0040]
    According to another embodiment, FIG. 3A is an enlarged cross section of an imbedded reinforcing strand 1 e provided as an imbedded core of a composite strand 1 to be arranged with other strands 1 in a corresponding array of strands 1 and 1 e. Each imbedded reinforcing strand 1 e is smaller in cross section, or size, than the strands 1, such that each of the strands 1 e is recessed in the array of strands 1 an 1 e, and is recessed below the polishing surface formed by the coating 3 applied to the strands 1. In addition, each imbedded strand 1 e is embedded in a material that may comprise a polishing material that forms a remainder of the strand 1 in which the strand 1 e is imbedded.
  • [0041]
    One or more of the reinforcing strands 1 e in a corresponding underlay provides the underlay with resistance to tearing. The reinforcing strand 1 e is made of a tensile resistant material, such as metal, glass fiber, or a polymer, such as, Nylon™. The flexibility and stiffness of the reinforcing strand 1 e is selected by the choice of material and the choice of cross section size.
  • [0042]
    Typically, fabrics of polyamides or polyesters such as “PET” poly(ethylene terephthalate) are selected for the underlay 12. It is possible to use a needled web provided that the web can be formed with openings 2 therein that penetrate the entire thickness of the web. Other flexible underlays 12 can be used such as a non-corrosive metal (such as aluminum or stainless steel) having openings 2 therein. Other underlays 12 are plastic sheets having openings 2 through the sheet of plastic, for example, polyamides, polyimides, and polyester, particularly “PET” poly(ethylene terephthalate). Laminated combinations of plastic sheets also can be used for the underlay 12.
  • [0043]
    To obtain adequate adhesion of the coating 3, of the polishing material, to the underlay 12, the underlay 12 may require a primer or an adhesion promoter. Upon curing from a liquid phase to a solid phase, the coating 3 adheres to the strands 1 of the underlay 12 to fix them in place, as well as, to coat the strands 1 to provide the polishing surface for the polishing pad 10. According to an embodiment, the strands 1 comprise a further polishing material that underlies the coating 3. The composite strand 1 disclosed by FIG. 3A comprise a further polishing material covering the reinforcing strand 1 e at its core. As the coating 3 is worn away, underlying strands 1 of further polishing material form the polishing surface on the polishing pad 10.
  • [0044]
    The following examples illustrate the invention. All numbers and percentages are on a weight basis unless otherwise specified.
  • EXAMPLE 1
  • [0045]
    A sheet of 75 micron thick polyethylene terephthalate (PET) film, precoated with an adhesion promoting coating and containing openings about 2 microns in diameter and about 100 openings per square cm. was roller coated using a conventional roller coater with an aqueous based latex. The latex was then cured at an elevated temperature to form a polishing layer. The aqueous based latex was a urethane latex (W242 from Witco). The resulting coated sheet has a polishing layer and has openings therein of about 0.3 microns. The sheet was die cut into a 71 cm. diameter pad. A film of a pressure sensitive adhesive was applied to the back of the pad and the pad was attached to a polishing machine described below.
  • [0046]
    The pad was used to polish TEOS oxide films deposited on silicon wafers. Polishing was performed on a Strasbaugh 6DS-SP using a down-force of 7 psi, platen speed of 35 rpm and a carrier speed of 37 rpm. The slurry was ILD1300 from Rodel, used at a flow rate of 125 mil/min. No pad conditioning was done either during polishing or between wafers. Wafers that were polished had excellent planarization, good surface appearance and excellent removal rate of material.
  • EXAMPLE 2
  • [0047]
    This example demonstrates the ability to achieve good polishing performance with a pad made by using a PET fabric as the flexible underlay. Abrasive is incorporated into the polishing layer of the pad and the pad is used with a particulate-free reactive liquid to polish tungsten.
  • [0048]
    A PET fabric was woven using PET fibers in a weaving pattern designed to provide approximately 1000 openings per square cm. having openings about 1.2 microns. The fabric was precoated with an adhesion promoting coating and the fabric was then roller coated with a filled latex formulation and cured. The filled latex formulation consisted of a mixture of an aqueous based latex (Vinyl Acetate-Ethylene emulsion, A460, from Air Products) and an abrasive filler of 0.25 micron alumina. The filler loading was 75% based on dry weight of total formulation and total percent solids was 70%. The filled latex formulation was applied to the fabric with a roller coater. This forced the latex formulation material through the fabric resulting in discrete openings in the fabric. The latex layer was cured at 60 C. in an oven to form a fabric having uniform openings penetrating the fabric. The fabric was die cut into a 71 cm. diameter polishing pad. A film of a pressure sensitive adhesive was applied to the back of the pad and the pad was attached to a polishing machine described below.
  • [0049]
    The polishing pad attached to the polishing platen of a Leco AP-300 polishing machine, using a down force of 7 psi, platen speed of 56 rpm and a carrier speed of 150 rpm. The pad was used in conjunction with a particulate-free reactive liquid based on potassium iodate as the oxidizing component (MSW2000B from Rodel Inc.), used at a delivery rate of 20 ml/min. A tungsten film was polished with the pad and a stable 7 grams/min. removal rate of tungsten was achieved.
  • [0050]
    Although embodiments of the invention are disclosed, other embodiments and modifications are intended to be covered by the spirit and scope of the appended claims.
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Classifications
U.S. Classification451/527
International ClassificationB24B37/26, B24D11/02, B24D11/00
Cooperative ClassificationB24D11/02, B24D11/005, B24B37/26
European ClassificationB24B37/26, B24D11/00B3, B24D11/02
Legal Events
DateCodeEventDescription
Sep 4, 2001ASAssignment
Owner name: RODEL HOLDINGS, INC., DELAWARE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:RHOADES, ROBERT L.;REEL/FRAME:012150/0965
Effective date: 20010607