Ultra high void volume polishing pad with closed pore structure

Abstract

The invention provides a polishing pad for chemical-mechanical polishing comprising a porous polymeric material, wherein the polishing pad comprises closed pores and wherein the polishing pad has a void volume fraction of 70% or more. Also disclosed is a method for preparing the aforesaid polishing pad and a method of polishing a substrate by use of theaforesaid polishing pad.

1 . A polishing pad for chemical-mechanical polishing comprising a porous polymeric material, wherein the polishing pad comprises closed pores and wherein the polishing pad has a void volume fraction of 70% or more. 
     
     
         2 . The polishing pad of  claim 1 , wherein the polishing pad has a void volume fraction of about 80% or more. 
     
     
         3 . The polishing pad of  claim 1 , wherein the porous polymeric material is formed from a polymer resin having a Shore D hardness according to ASTM D2240 of about 15D to about 75D. 
     
     
         4 . The polishing pad of  claim 3 , wherein the porous polymeric material is formed from a polymer resin having a Shore D hardness according to ASTM D2240 of about 25D to about 72D. 
     
     
         5 . The polishing pad of  claim 1 , wherein the pores have an average pore size of about 5 pin to about 200 μm. 
     
     
         6 . The polishing pad of  claim 1 , wherein the polishing pad has a compressibility of about 5% or more. 
     
     
         7 . The polishing pad of  claim 1 , wherein the polishing pad has a storage modulus of elasticity of about 1 MPa or less. 
     
     
         8 . The polishing pad of  claim 1 , wherein the polishing pad comprises a polymer resin selected from the group consisting of thermoplastic elastomers, thermoplastic polyurethanes, polyolefins, polycarbonates, polyvinylalcohols, nylons, elastomeric rubbers, styrenic polymers, polyaromatics, fluoropolymers, polyimides, cross-linked polyurethanes, cross-linked polyolefins, polyethers, polyesters, polyacrylates, elastomeric polyethylenes, polytetrafluoroethylenes, polyethyleneteraphthalates, polyimides, polyaramides, polyarylenes, polystyrenes, polymethylmethacrylates, copolymers and block copolymers thereof, and mixtures and blends thereof. 
     
     
         9 . The polishing pad of  claim 8 , wherein the polymer resin is a thermoplastic polyurethane. 
     
     
         10 . A method of preparing a polishing pad, which method comprises:
 (a) providing a polishing pad material comprising a polymer resin,   (b) subjecting the polishing pad material to an inert gas at a first elevated pressure,   (c) foaming the polishing pad material by increasing the temperature of the polishing pad material to a first temperature above the glass transition temperature of the polishing pad material and less than the melting temperature of the polishing pad material,   (d) subjecting the polishing pad material to an inert gas at a second elevated pressure, and   (e) foaming the polishing pad material by increasing the temperature of the polishing pad material to a second temperature above the glass transition temperature of the polishing pad material and less than the melting temperature of the polishing pad material.   
     
     
         11 . The method of  claim 10 , wherein the gas comprises nitrogen, carbon dioxide, or combinations thereof. 
     
     
         12 . The method of  claim 11 , wherein the gas is carbon dioxide, and the first and second pressures are about 1 MPa to about 20 MPa. 
     
     
         13 . The method of  claim 10 , wherein the polishing pad comprises a polymer resin selected from the group consisting of thermoplastic elastomers, thermoplastic polyurethanes, polyolefins, polycarbonates, polyvinylalcohols, nylons, elastomeric rubbers, styrenic polymers, polyaromatics, fluoropolymers, polyimides, cross-linked polyurethanes, cross-linked polyolefins, polyethers, polyesters, polyacrylates, elastomeric polyethylenes, polytetrafluoroethylenes, polyethyleneteraphthalates, polyimides, polyaramides, polyarylenes, polystyrenes, polymethylmethacrylates, copolymers and block copolymers thereof, and mixtures and blends thereof. 
     
     
         14 . The method of  claim 12 , wherein the polymer resin is a thermoplastic polyurethane. 
     
     
         15 . A method of polishing a substrate, comprising:
 (a) providing a substrate to be polished,   (b) contacting the substrate with a polishing system comprising the polishing pad of  claim 1  and a polishing composition, and   (c) abrading at least a portion of the substrate with the polishing system to polish the substrate.