Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/11—Lapping tools
  • B24B37/20—Lapping pads for working plane surfaces
  • B24B37/24—Lapping pads for working plane surfaces characterised by the composition or properties of the pad materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/11—Lapping tools
  • B24B37/20—Lapping pads for working plane surfaces
  • B24B37/26—Lapping pads for working plane surfaces characterised by the shape of the lapping pad surface, e.g. grooved
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/35—Composite foams, i.e. continuous macromolecular foams containing discontinuous cellular particles or fragments
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/10—Water or water-releasing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
  • C08J2203/142—Halogenated saturated hydrocarbons, e.g. H3C-CF3

Definitions

• the present invention is generally related to a self-conditioning polishing pad, comprising an insoluble polymeric foam matrix containing insoluble polymeric foam particles coated with a water-soluble component.
• the pad surface which contacts the part to be polished is typically conditioned before and during polishing.
• One problem encountered during the use of polyurethane foam polishing pads is the continuous need to recondition the pad. Conditioning in most polishing applications involves moving a conditioning tool across the pad contact surface which creates a nap of sheared polyurethane, flattens out pad topography, and cleans out accumulated slurry and swarf from pores.
• a conditioning tool can comprise a metal puck that is impregnated on one side with diamond powder or another similarly hard abrasive material, in the normal course of polishing, a polishing pad will experience a decline in performance (i.e., Stock removal, part flatness, part defects, and/or surface roughness) that is related to the flattening of the polyurethane nap, changes in the pad topography, and clogging of pores with slurry and swarf.
• a decline in performance i.e., Stock removal, part flatness, part defects, and/or surface roughness
• Polishing pads are useful in many applications. Two such applications are polishing glass and polishing wafers. Regardless of the application, a polishing pad is moved relative to the object (e.g., glass, Si wafer. Sapphire wafer, etc.) being polished. This relative movement may be created by rotating the polishing pad. by rotating the object being polished, or a combination of such movements. Other linear or any useful relative motion may be used between the polishing pad and the object being polished, in some embodiments, a force may be applied to press the polishing pad in contact with the wafer.
• the object e.g., glass, Si wafer. Sapphire wafer, etc.
• Other linear or any useful relative motion may be used between the polishing pad and the object being polished, in some embodiments, a force may be applied to press the polishing pad in contact with the wafer.
• the polishing may be performed to varying degrees such as to remove larger imperfections, to achieve a mirror finish and/or final flatness, etc.
• the process of polishing silicon semiconductor substrate wafers to improve flatness is accomplished by a mechanoehemical process in which one or more polishing pads, typically made of ureihane, is used with an alkaline polishing solution
• I slurry
• the silicon wafer is supported between a platen covered with a polishing pad and a carrier to which the wafer is attached, or, in the case of double-sided polishing, the wafer is held between two platens, each covered with a polishing pad.
• the pads are typically about i mm thick and pressure is applied to the wafer surface.
• the wafer is eehanochemically polished by relative movement between the platen and the wafer,
• polishing tools During polishing, pressure is applied to the wafer surfaces by pressing the pad and the wafer together in a polishing tool, whereby a uniform pressure is generated over the entire surface owing to the compressive deformation of pads. Polishing tools often have dynamic heads which can be rotated at different rates and at varying axes of rotation. This removes material and evens out any irregular topography, making the wafer flat or planar.
• polishing pads tend to need to be conditioned and therefore replaced frequently because conditioning removes a portion of the pad thickness. For example, such polishing pads may need to be replaced every 5-10 days. It is desirable to have a polishing pad that can maintain its optimal polishing performance longer before conditioning is necessary, thereby giving the polishing pad a longer polishing life, in this manner, more polishing can be performed and thus more product can be made in a set period of time. In this regard, it is desirable to have a polishing pad that is self conditioning.
• the present invention is directed to a self-conditioning polishing pad.
• the self- conditioning polishing pad comprises an insoluble polymeric foam matrix and insoluble polymeric foam particles within the foam matrix.
• the particles are coated with a water- soluble component over a portion of the surface area of the particle.
• the particles may have a diameter in the range of 5 to 1000 microns in diameter,
• Figure 1 illustrates a cross section of a self conditioning polishing pad in accordance with one exemplary embodiment of the present invention
• Figure 2 illustrates a self conditioning polishing pad, the part to be polished, and a polishing tool, all in accordance with one exemplary embodiment of the present invention
• Figure 3 illustrates an exemplary method flow chart for manufacturing an exemplary self conditioning pad in accordance with one exemplary embodiment of the present invention.
• a polishing pad for use in polishing glass, silicon semiconductor substrate wafers, and Sapphire wafers (among other things).
• the polishing pad is chemically and/or physically configured to comprise particles formed in the pad in such a manner that the pad is a self-conditioning pad, Stated another way, the pad can he configured to self condition so as to effectively function for longer periods of time without interruption of operation for conditioning relative to pads that are not so configured,
• a polishing pad may comprise a foam matrix and foam particles within the ioam matrix, in an exemplary embodiment, the polishing pad comprises an insoluble polymeric foam matrix and insoluble polymeric foam particles within the insoluble polymeric foam matrix.
• the insoluble polymeric foam particles may be coated over a portion of the particles' surface area with a water soluble component.
• a polishing pad 100 comprises an insoluble polymeric foam matrix 1 10 and insoluble polymeric foam particles 120 within insoluble polymeric foam matrix 1 10,
• the insoluble polymeric foam particles 120 may be coated over a portion of the particles' surface area with a water-soluble coating 125.
• the insoluble polymeric foam particles 120 are coated over a portion comprising about 5 to 90% of the particles' surface area with a water-soluble component 125.
• insoluble polymeric foam particle 120 and water-soluble coating 125 together form a coated particle 130
• the insoluble foam matrix 1 J O further comprises a pore 170.
• a pore 170 comprises a cell opening 140.
• a coated particle 130 may further comprise a pore 180.
• insoluble, polymeric foam particles 120 are formed by first making a larger insoluble polymeric foam object and then creating smaller particles out of the larger foam object.
• the smaller particles can be formed out of the larger foam object through any suitable method.
• the larger foam object is ground into smaller particles.
• the insoluble foam particles may be formed by cryogenically grinding the larger foam object, in other exemplary embodiments, particles may be formed in a hammer mill.
• any other suitable method for forming particles may be used.
• the insoluble polymeric foam particles have a diameter between about 5 and 500 microns, in another exemplary embodiment, the insoluble polymeric foam particles comprise at least one of: a surfactant, an etehant. a pH buffer, an acid, and a base. Moreover, in another exemplary embodiment, the insoluble polymeric foam particles have a bulk density of about 0.2 to 0.85 g/cm A 3.
• particles 120 are coated with a soluble coating
• particles 120 are coated through use of a spray coating or other suitable technology such as a cyclonic powder coater.
• particles 120 are formed by making slurry of insoluble particles contained in a soluble liquid phase then drying and finally cryogrindmg or hammer milling the solidified insoluble particle/soluble composite into particles.
• particles 120 are dried and clarified after the spray coating.
• a coated particle 130 comprises a particle 120 thai is coated with a soluble coating 125.
• the insoluble polymeric foam particles are coated over about 5% to 90% of the surface area of said insoluble polymeric foam particles.
• Coating of 5% to 90% of the insoluble foam particles can be accomplished, for example, by calculating the surface area of the particles and then proportionally blending the appropriate amount of water soluble polymer.
• the coated particles comprise about 10% to 90% by volume of the polishing pad.
• the soluble coating is comprised of organic or inorganic water-soluble particles.
• organic water- soluble particles include particles of saccharides (polysaccharides, e.g., a, (3 or y- cyclodextrin, dextrin and starch, lactose, mannite, and the like), celluloses (hydroxypropyl cellulose, methykellulose, and the like), proteins, a polyvinyl alcohol, a polyvinyl pyrroiidone, a polyacrylic acid, a poiyacrylate, a polyethylene oxide, water-soluble photosensitive resins, a sulfonated polyisoprene, and a sulfonated polyisoprene copolymer.
• saccharides polysaccharides, e.g., a, (3 or y- cyclodextrin, dextrin and starch, lactose, mannite, and the like
• celluloses hydroxypropyl cellulose, methykellulose, and the like
• proteins
• coated particles 130 are added into the mix during the process of forming matrix 1 10 of polishing pad 100.
• coated particles 130 will be set within matrix 1 10.
• coated particles 130 are mixed into the matrix using high-shear blending
• Other mixing methods include double planetary, kneading swing arm, and inline mixing with direct filler feed.
• any method of mixing may be used that is configured to randomly space out coated particles 130 within matrix 3 1 0.
• the mixing process may entrain air bubbles within the foam (whether it be within the foam particles when forming them, or whether it may be within matrix 1 10).
• any suitable method for introducing pores 140 within matrix 1 10 or for introducing pores 180 within particles 120 may be used.
• These methods may include ambient air frothing, water biown-C0 2 evolution, physical blowing agents such as HFC, decompositional blowing agents such as azonitriles, microspheres, and injected inert gasses.
• the insoluble foam object (that is to become the insoluble foam particles) is formed by mixing a polyurethane prepolymer, a curing agent, a surfactant, and a foaming agent.
• an abrasive filler may also be mixed with the other ingredients.
• the insoluble foam object can be polyurethane foam, epoxy foam, polyethylene foam, polybutadiene foam, ionomer foam, or any other insoluble polymer foam.
• the insoluble foam object may then be ground down into smaller insoluble foam particles 120. These particles 120 may then be coated to form insoluble coated foam particles 130. The coated particles 130 may then be included in the formation of the overall pad 100.
• polishing pad 100 is then formed by mixing a prepolymer, a ctsring agent, a surfactant, a foaming agent, and coated particles 130.
• an abrasive filler may also be mixed with the other ingredients.
• the insoluble foam matrix can be polyurethane foam, epoxy foam, polyethylene foam, polybutadiene foam, jonomer foam, or any other insoluble polymer foam.
• the components may be mixed together using high-shear blending to incorporate the coated particles into the matrix.
• a foam bun may be formed in an open mold. The foam bun may be cured and then sliced into sheets. Each sheet comprises one polishing pad 100. In an exemplary embodiment, the pad comprises open ceils 140.
• the open cell content of the insoluble polymeric foam particle may be about 5% to about 75%.
• the soluble component coating the insoluble foam particle may be between 50% and 100% soluble.
• the insoluble polymeric foam matrix has a bulk density of 0.2 to 0.85 g/cm A 3.
• the foam bun may have an aggregate bulk density of 0.2 to 0.85 g/cra A 3.
• Matrix 1 10 and particle 120 are both made of an insoluble foam material.
• the materials tor matrix 1 10 and particle 120 are identical to each other.
• scrap material that is a byproduc of the production process can be used to create additional particles.
• the materials are different from each other.
• the matrix and particle materials may he selected from any of a number of possible materials.
• the insoluble foam material for either of matrix 1 10 and/or particle 120 may be made from a polymer foam.
• the polymer foam may be polyurethane, polyethylene, polystyrene, polyvinyl chloride, aery! foam or a mixture thereof.
• These polymer foams may be produced by mixing a polymerizing agent, for example, an isocyanate-terminated monomer, and a prepoiymer, for example an isocyanate functional polyol or a poiyol-diol mixture.
• classes of polymerizing agents orisocyanate-terminated monomers, that may be used to prepare the particulate crosslinked polyurethane include, but are not limited to, aliphatic polyisocyanates; ethylenieally unsaturated polyisocyanates; alicyclic polyisocyanates; aromatic polyisocyanates wherein the isocyanate groups are not bonded directly to the aromatic ring, e.g., xylene diisocyanate; aromatic polyisocyanates wherein the isocyanate groups are bonded directly to the aromatic ring, e.g., benzene diisocyanate; halogenated, alkylated, alkoxylated, nitrated, carbodiimide modified, urea modified and biuret modified derivatives of polyisocyanates belonging to the.se classes; and dimerized and trimerized products of polyisocyanates belonging to these classes.
• aliphatic polyisocyanates from which the isocyanate functional reactant may be selected include, but are not limited to, ethylene diisocyanate, trimethylene o diisocyanaie, tetrantethylene diisoeyanate, hexamethylene diisocyanaie (HDD, octamethylene diisoeyanate, nonamethylene diisoeyanate, dimethylpentane diisoeyanate, trimethylhexane diisoeyanate, dec methyiene diisoeyanate, trimethyihexamethylene diisoeyanate, undecanetnisocyanate, hexamethylene triisocyanate, diisocyanato- (Isoeyanatomethyl)octane, trimethyl-diisoeyanato (isocyanatomethy!)octane, bis(isoeyanatoethyl) carbonate, bis(isocyanato
• Examples of ethyjenieal!y unsaturated polyisocyanates from which the isocyanate functional reactant may be selected include, but are not limited to, butene diisoeyanate and butadiene diisoeyanate.
• ASicyclie polyisocyanates from which the isocyanate functional reactant may be selected include, but are not limited to, Lsophorone diisoeyanate (IPDi), eyclohexane diisoeyanate, methyteyclohexane diisoeyanate, bis(isocyanatonjethyl) eyclohexane, bis(isocyanatocyeiohexyl) methane, bis(isocyanatocyclohexyl) propane, bis(isocyanatocyclohex J) ethane, and isocyanatomethyl-(isocyanatopropyl)- isocyanatoraethyl bicycl
• aromatic polyisocyanates wherein the isocyanate groups are not bonded directly to the aromatic ring from which the isocyanate functional reactant may be selected include, but are not limited to, bis(isocyanatoethyl) benzene, tetramethylxylene diisocyanaie, bis(isoeyanato-rnethyiethyl) benzene, bis(ssocyanatobutyl) benzene, bis(isocyanatomethyi) naphthalene, bis(isoeyanatomethyl)diphenyl ether, bis ⁇ isocyanatoethyl)phthalate, mesitylene triisoeyanate and di(isoeyanatomethyl) fiiran.
• Aromatic polyisocyanates having isocyanate groups bonded directly to the aromatic ring, from which the isocyanate functional reactant may be selected include, but are not limited to, phenylene diisoeyanate, ethylphenylene diisoeyanate, isopropylphenyiene diisoeyanate, dimethylpheny lene diisoeyanate, diethylphenylene diisoeyanate, diisopropyipbenylene diisoeyanate, trimethy!benzene triisocyanate, benzene triisocyanate, naphthalene diisoeyanate, raethylnaphtha!ene diisoeyanate, biphemd diisoeyanate, ortho-tolidine diisoeyanate, diphenylmethane diisoeyanate, bis(methy)-isocyanatophenyl) me
• polyisocyanate monomers having two isocyanate groups include, xylene diisocyanaie, ietramethylxyiene diisocyanaie, isophorone diisocyanaie, bis(isocyanaiocydohexy1)meihane, toluene diisocyanaie (TDI), diphenylmethane diisocyanaie (MDI), and mixtures thereof.
• isocyanate functional polyols include, but are not limited to, polyether poiyois, polycarbonate poiyois, polyester poiyois and polycaprolactone poiyois.
• commercial prepolymers may be used, for example Adiprene ⁇ L213 a TDI, terminated polyether based (PTMEG),
• the molecular weight of the prepolymers can vary widely, for example, having a number average molecular (Mn) of from 500 to 15,000, or from 500 to 5000, as determined by gel permeation chromatography (GPC) using polystyrene standards.
• Mn number average molecular
• Classes of poiyois that may be used to prepare the isocyanate functional prepolymers of the first component of the exemplary two-component composition, used to prepare the exemplary particulate crossiinked poiyurethane include, but are not limited to: straight or branched chain alkane poiyois, e.g., ethanediol, propanediol, propanediol, butanediol, butanediol, glycerol, neopentyl glycol, trimethylolethane, tritnetbyloSpropane, di- trimethylolpropane, erythritoL pentaerythritol and di-pentaeryihritoi; polyaikyiene glycols, e.g., di-, tri- and tetraethylene glycol, and di-, tri- and tetrapropylene glycol; cyclic alkane polyols,
• the isoeyanate functional pofyurethane prepolymer is prepared from a diisoeyanate, e.g., toluene diisocyanate, and a polyalkylene glycol, e.g., poly(tetrahydrofuran) with an M n of ⁇ 000,
• the isoeyanate functionai polyurethane prepolymer may optionally be prepared in the presence of a catalyst.
• a catalyst include, but. are not limited to, tertiary amines, such as triethylamine, and organometailic compounds, such as dibutyltin dila rate.
• an abrasive filler may also form part of the insoluble foam particle 120 and/or insoluble foam matrix 1 10,
• This abrasive filler may include exemplary abrading particles that include, but are not limited to, particles of, for example, cerium oxides, silicon oxides, aluminum oxides, zsreonia, iron oxides, manganese dioxides, kaolin clays, montmorillonite clays, and titanium oxides.
• exemplary abrading particles may include, but are not limited to, silicon carbides and diamond.
• urethane polymers for polishing pads with a single mixing step that avoids the use of tsocyanate-terminated monomers.
• a prepolymer is mixed, for example, in an open-air container with the use of a high-shear impeller.
• atmospheric air is entrained in the mix by the action of the impeller, which pulls air into the vortex created by the rotation.
• the entrained gas bubbles act as nucleation sites for the foaming process.
• a blowing agent such as water, may be added to the mix to facilitate a reaction which produces the CO? gas responsible for cell growth.
• the prepolymer may be reacted with a foaming agent such as, 4 > 4'-methylene-bis-o-chIoroaniIine [MBC or MOCA],
• MOC 4 > 4'-methylene-bis-o-chIoroaniIine
• the MOC may initiate polymerization and chain extension, causing the viscosity of the mix to increase rapidly.
• the mix may be poured into the mold during this window.
• the window quickly after the pour, the window passes, and existing pores become effectively frozen in place. Although pore motion may essentially have ended, pore growth may continue, for example, as CG-> continues to be produced from the polymerization reaction. In one example embodiment, the molds then oven cure to substantially complete the polymerization reaction, for example, for 6-12 hours at 1 15 C.
• the molds are removed from the oven, and ailowed to cool, At this point, a cured moid (one formed without particles) may be broken up into particles tor use in a subsequent pad forming process, If the cured mold contains the coated particles, it may be sliced using a skiver, in one example embodiment, the slices may be made into circular pads or rectangular-shaped pads or pads of any other desired shape. For example, the slices may be made by cutting to shape with a punch or cutting tool or any other suitable instrument, in some example embodiments, an adhesive may be applied to one side of the pad.
• the pad surface may ⁇ be grooved, if desired, for example, on the polishing surface in a pattern such as a cross- hatched pattern (or any other suitable pattern), In some example embodiments, at that point, the pads are generally ready for use.
• the geometry or shape of grooves may comprise at least one of a square trough, a rounded trough, and a triangular trough.
• numerous physical configurations of various geometries to the polishing pad surface are contemplated in this disclosure.
• any arrangement, combination, and/or application of soluble coated insoluble foam particles within an insoluble foam matrix applicable for a single pad wouid work for a plurality of pads stacked on each other.
• a stacked pad may comprise one such pad 100 as disclosed herein as well as a typical pad.
• grooves can be created via any mechanical method capable of producing grooves in a polymer foamed polishing pad.
• grooves can be created with a circular saw blade, a punch, a needle, a drill, a laser, an air-jet, a water jet, or any other instrument capable of rendering grooves in the pad.
• grooves can be made simultaneously with a multiple gang-saw jig, a multiple-drill bit jig, a multiple punch jig, or a multiple-needle jig.
• the polishing pad may be chemically configured to comprise a chemical foaming agent applied to the open-air mix while in the liquid phase.
• the chemical foaming agent comprises at least one of a hydrofiourocarbon (HFC) or azeotrope of 2 or more hydrocarbon (HFCs), such as 1,1 , 1 ,3,3-pentaflourobutane (HFC-365); 1, 1 ,1,2- tetraflouroethane (HFC- 134a), methoxy-nonafluorobutane ( lFE-7100) and a free radical initiator comprising an azonitrile, such as 2,4-Dimethyl, 2,2'-Azobis Pentanenitrile.
• HFC hydrofiourocarbon
• HFCs 1,1 , 1 ,3,3-pentaflourobutane
• HFC- 134a 1, 1 ,1,2- tetraflouroethane
• lFE-7100 methoxy-n
• Exemplary foaming agents include the HFCs Solkane® 365mfc and 134a (Solvay, Hannover, Germany), and free radical initiators Vazo 52 (Dupont Wilmington, DE),
• HFCs Solkane® 365mfc and 134a Solvay, Hannover, Germany
• free radical initiators Vazo 52 Vazo 52 (Dupont Wilmington, DE)
• numerous chemical foaming agents can be incorporated into the polishing pad and are contemplated in this disclosure.
• the chemical configuration comprises a cell opener which promotes cell opening during the interaction of two ceils in the liquid phase.
• cell openers include, but are not limited to non-h rdrol izable polydimethylsiioxanes, po!yalkyieoxides, dimethyisiioxy, methyipoiyethersiloxy, silicone copolymers, wherein in some exemplary embodiments, the silicone copolymers can be Dabco DC-3043 or Dabco DC-3042 (Air Products, Ailentown, PA).
• the output of a gas injector can be inserted directly into the open-air mix, causing the injection of more bubbles than would otherwise be introduced through the action of the impeller alone.
• a method of forming a pad includes the step of directly introducing gas bubbles into the air-mix in the liquid phase. This step of directly introducing gas bubbles may involve the selection of the size and quantity of bubbles.
• polishing pad 100 may be used in connection with a polishing table 220, a slurry 230, and a platen 240 for holding the object 210 io be polished.
• the pad 100 may be moved relative to the object 210 being polished.
• downward pressure may be applied to a platen 240, in some exemplary embodiments, platen 240 may be twisted or translated or otherwise moved to facilitate polishing, in some example embodiments, polishing table 220 ma be twisted or translated or otherwise moved to facilitate polishing.
• the pad 100 may self condition such that polishing may occur for a longer period of time than for a traditional polishing pad that is not so configured, in one exemplary embodiment, the polishing pad Is never reconditioned.
• the embedding of these coated particles 120 facilitates reduced conditioning or may eliminate conditioning of the pad 100 because, as the particles 120 are exposed during polishing, the water soluble coating 125 will cause those particles to gradually become detached from the surface of the pad, Stated another way, the water-soluble coating 125 surrounding exposed particles 150 may dissolve and release the exposed particles 150 from the pad. This action generates new holes in the surface and eventually exposes yet further coated particles.
• Such self conditioning may reduce the need to "rake" the pad, and cause the pad to last longer.
• the insoluble polymeric foam particles are coated over about 5% to 90% of the surface area of said insoluble polymeric foam particles.
• the partial nature of the water-soluble coating over the surface area of the insoluble polymeric foam particles allows the insoluble foam matrix to interface with insoluble portions of the foam particles, retaining the foam particle by providing a poiyurethane-polyurethane bond with the pad matrix in an exemplary embodiment and retarding the release of the foam particles from the pad as the water-soluble coating surrounding exposed particles dissolves.
• the progressive dissolving of the water-soluble coating progressively diminishes the strength of the bond between the particles and the matrix. Accordingly, if the insoluble polymeric foam particles are coated over an insufficient percentage of die surface area of said insoluble polymeric foam particles, the bond between the particles and the matrix would not sufficiently diminish over time and the release of the particles from the pad may be impeded, This may retard the generation of new holes in the surface. On the other hand, if the insoluble polymeric foam particles are coated over an excessive percentage of the surface area of said insoluble polymeric foam particles, the bond between the particles and the matrix would diminish prematurely or excessively as the water soluble coating dissolved, releasing the particle prematurely, This may diminish the life of the pad or potentially change the polishing characteristics of the pad,

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• Engineering & Computer Science (AREA)
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• Mechanical Engineering (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Mechanical Treatment Of Semiconductor (AREA)

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• 2013
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