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  Polishing padUSPTO Application #: 20060183412Title: Polishing pad Abstract: A polishing pad is described as comprising, (a) particulate polymer which can be chosen from particulate thermoplastic polymer (e.g., particulate thermoplastic polyurethane), particulate crosslinked polymer (e.g., particulate crosslinked polyurethane and/or particulate crosslinked polyepoxide) and mixtures thereof; and (b) organic polymer binder (e.g., polyurethane binder and/or polyepoxide binder), which can bind the particulate polymer together, wherein said organic polymer binder can be prepared in-situ . The particulate polymer and organic polymer binder can be distributed substantially across the work surface the polishing pad, and the pad can have a percent pore volume of from 2 percent by volume to 50 percent by volume, based on the total volume of said polishing pad. (end of abstract)
Agent: Ppg Industries Inc Intellectual Property Dept - Pittsburgh, PA, US Inventors: William C. Allison, Robert G. Swisher, Alan E. Wang USPTO Applicaton #: 20060183412 - Class: 451526000 (USPTO) Related Patent Categories: Abrading, Flexible-member Tool, Per Se The Patent Description & Claims data below is from USPTO Patent Application 20060183412. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS -REFERENCE TO RELATED APPLICATION [0001] This application is a division of U.S patent application Ser. No. 10/317,982, filed on Dec. 13, 2002. [0002] The present invention relates to a polishing pad. In particular, the polishing pad of the present invention can be porous and, can comprise particulate polymer and an organic polymer binder. The polishing pad according to the present invention is useful for polishing articles, and is especially useful for chemical mechanical polishing or planarization of microelectronic and optical electronic devices such as but not limited to semiconductor wafers. [0003] The polishing or planarization of a rough surface of an article such as a microelectronic device, to a substantially smooth surface generally involves rubbing the rough surface with the work surface of a polishing pad using a controlled and repetitive motion. A polishing fluid can be interposed between the rough surface of the article that is to be polished and the work surface of the polishing pad. [0004] The fabrication of a microelectronic device can comprise the formation of a plurality of integrated circuits on a semiconductor substrate. The composition of the substrate can include silicon or gallium arsenide. The integrated circuits generally can be formed by a series of process steps in which patterned layers of materials, such as conductive, insulating and semiconducting materials, are formed on the substrate. In order to maximize the density of integrated circuits per wafer, it is desirable to have a planar polished substrate at various stages throughout the production process. As such, production of a microelectronic device typically involves at least one polishing step and can often involve a plurality of polishing steps, which can result in the use of more than one polishing pad. [0005] The polishing step can include rotating the polishing pad and the semiconductor substrate against each other in the presence of a polishing fluid. The polishing fluid can be mildly alkaline and can optionally contain an abrasive particulate material such as but not limited to particulate cerium oxide, particulate alumina, or particulate silica. The polishing fluid can facilitate the removal and transport of abraded material off and away from the rough surface of the article. [0006] Polishing pad characteristics such as pore volume and pore size can vary from pad-to-pad and throughout the operating lifetime of a particular pad. Variations in the polishing characteristics of the pads can result in inadequately polished and planarized substrates which can be unsuitable for fabricating semiconductor wafers. Thus, it is desirable to develop a polishing pad that exhibits reduced pad-to-pad variation in polishing and planarization characteristics. It is further desirable to develop a polishing pad that exhibits reduced variations in polishing and planarization characteristics throughout the operating lifetime of the pad. [0007] In accordance with the present invention, there is provided a polishing pad comprising: (a) particulate polymer chosen from thermoplastic particulate polymers, crosslinked particulate polymers, particulate polymers comprised of interpenetrating polymer networks, and mixtures thereof; and (b) an organic polymer binder chosen from thermoplastic organic polymer binders, substantially crosslinked organic polymer binders, interpenetrating polymer networks, and mixtures thereof. [0008] The present invention further includes a polishing pad comprising particulate polymer and an organic polymer binder wherein said binder is formed in-situ Moreover, the present invention includes a polishing pad comprising particulate polymer and an organic polymer binder wherein there is no sintering of particles in said particulate polymer. [0009] As used herein and in the claims, the term "substantially uniformly across working surface of said pad" refers to the distribution of the particulate polymer and organic polymer binder such that the variation in physical characteristics of the pad is reduced, and the uniformity of the physical characteristics of the pad is enhanced. [0010] As used herein and in the claims, the terms "in-situ preparation of the binder", "in-situ polymerization of the binder" "in-situ formation of the binder", and similar terminology, refer to preparing, polymerizing and/or forming the organic polymer binder of the present invention in the presence of the particulate polymer. In a non-limiting embodiment, the molecules of a binder precursor can chemically react with each other to form the organic polymer binder while the precursor is in the presence of the particulate polymer. In another non-limiting embodiment, more than one binder precursor can be used and the molecules of one precursor can chemically react with the molecules of another precursor to form the organic polymer binder while in the presence of the particulate polymer. [0011] Suitable organic binder precursors for use in the present invention can be selected from a wide variety known to skilled artisans. Non-limiting examples can include monomers, prepolymers, resins and mixtures thereof. In a non-limiting embodiment, the organic binder precursor can comprise catalysts, crosslinking agents, curing agents, and other conventional additives that are known in the art. [0012] In a non-limiting embodiment, the percent pore volume of the polishing pad of the present invention can be calculated using the following equation, "100.times.(density of the pad).times.(pore volume of the pad)". The density (e.g., grams per cubic centimeter) can be determined in accordance with American Standard Test Method (ASTM) No. D 1622-88. The pore volume (e.g., cubic centimeters per gram) can be determined by means of a mercury porosimetry method in accordance with ASTM D 4284-88, using an Autopore III mercury porosimeter from Micromeritics. [0013] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless expressly and unequivocally limited to one referent. [0014] For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. [0015] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. [0016] FIG. 1 is a sectional representation of a polishing pad assembly according to the present invention; [0017] FIG. 2 is a sectional representation of a polishing pad assembly according to the present invention, which is similar to that of FIG. 1 but in which the adhesive means is an adhesive assembly; and [0018] FIG. 3 is a sectional representation of a polishing pad according the present invention, in which a portion of the pad, including a portion of the work surface of the pad, is shown in greater detail. FIGS. 1-3 are not to scale. In FIGS. 1-3, like numerals refer to the same structural components. [0019] In a non-limiting embodiment, the polishing pad of the present invention can comprise particulate polymer and an organic polymer binder. The organic polymer binder can bind together the particulate polymer. [0020] Non-limiting examples of suitable particulate polymer can include thermoplastic particulate polymers, crosslinked particulate polymers, and mixtures thereof. In a non-limiting embodiment, the particulate polymer can be chosen such that there is no sintering of the particles upon heating. As used herein and the claims, the term "no sintering" and related terms mean that there is minimal plastic flow at the boundary of the particulate polymer, and little to no coalescence between the particles of the particulate polymer in the polishing pad of the present invention. [0021] In a non-limiting embodiment, when the particulate polymer of the pad comprises particulate thermoplastic polymer, the polishing pad can be prepared below the melting or sintering point of the particulate thermoplastic polymer. In another non-limiting embodiment, the particulate polymer can comprise particulate crosslinked polymer which can have sintering point, and thus can be unsinterable. [0022] The polymer comprising the particulate polymer for use in the present invention can be prepared by various methods that are known to the skilled artisan. In alternate non-limiting embodiments, the polymer can be formed by a condensation reaction, or a free radical initiated reaction, or combinations thereof. In one non-limiting embodiment, the polymer can include a polyurethane formed by condensation polymerization of an isocyanate functional polyurethane prepolymer with a polyamine. In another non-limiting embodiment, the polymer can include a polyurethane-acrylate formed by free radical polymerization of a urethane-diacrylate in the presence of free radical initiator. In a further non-limiting embodiment, the polymer can include an interpenetrating polymer network formed by stepwise or simultaneous condensation and free radical polymerization reactions. As used herein and the claims, the term "interpenetrating polymer network" (IPN) refers to a combination of two polymers both in network form, at least one of which is synthesized or crosslinked in the immediate presence of the other. Unlike chemical blends, there are no induced covalent bonds between the two polymers. Thus, in addition to mechanical blending and copolymerization, IPNs represent another mechanism by which different polymers can be physically combined. [0023] The particulate polymer can be prepared by various methods that are known to the skilled artisan. In a non-limiting embodiment, bulk polymers can be cryogenically ground and classified into desired particle size ranges. In another non-limiting embodiment, the particulate polymer can be prepared directly by reacting a two-component composition comprising a polyisocyanate and an OH-containing material, in the presence of a liquid medium. In a further non-limiting embodiment, said liquid medium is heated and agitated. In another non-limiting embodiment, the liquid medium (such as but not limited to an aqueous medium) can be chosen such that the two-component composition can be substantially insoluble in the medium. In alternate non-limiting embodiments, the shape of the particulate polymer can be regular or irregular, and can include but is not limited to the following shapes: spherical, disk, flake and combinations or mixtures thereof. Continue reading... Full patent description for Polishing pad Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Polishing pad patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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