Polyurethane urea polishing pad

Abstract

The present invention relates to an article for altering a surface of a workpiece, or a polishing pad having a window. In particular, the polishing pad includes a polyurethane urea material wherein the polyurethane urea material contains cells which are at least partially filled with gas. The polyurethane urea material can be prepared by combining polyisocyanate and/or polyurethane prepolymer, hydroxyl-containing material, amine-containing material and blowing agent. 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. The window of the polishing pad is at least partially transparent and thus, can be particularly useful with polishing or planarizing tools that are equipped with through-the-platen wafer metrology.

1 . A pad adapted to polish a microelectronic substrate, said pad comprising: 
 a. a polyurethane urea-containing polishing layer, said polishing layer comprising at least partially gas-filled cells, at least a portion of said at least partially gas-filled cells formed by an in-situ reaction, wherein an opening is formed in said polishing layer; and    b. a second layer wherein at least a portion of said second layer comprises an at least partially transparent window,    wherein said polishing layer is at least partially connected to said second layer, and said opening in said polishing layer is at least partially aligned with said window of said second layer.    
     
     
         2 . A pad adapted to polish a microelectronic substrate, said pad comprising: 
 a. a polyurethane urea-containing polishing layer, said polishing layer comprising at least partially gas-filled cells, said polishing layer formed by reaction of polyurethane prepolymer with amine-containing material and blowing agent, wherein an opening is formed in said polishing layer; and    b. a second layer wherein at least a portion of said second layer comprises an at least partially transparent window,    wherein said polishing layer is at least partially connected to said second layer, and said opening in said polishing layer at least partially aligns with said window of said second layer.    
     
     
         3 . A pad adapted to polish a microelectronic substrate, said pad comprising: 
 a. a polyurethane urea-containing polishing layer, said polishing layer comprising at least partially gas-filled cells, said polishing layer formed by reaction of polyisocyanate with hydroxyl-containing material, amine-containing material and blowing agent, wherein an opening is formed in said polishing layer; and    b. a second layer wherein at least a portion of said second layer comprises an at least partially transparent window,    wherein said polishing layer is at least partially connected to said second layer, and said opening in said polishing layer at least partially aligns with said window of said second layer.    
     
     
         4 . A pad adapted to polish a microelectronic substrate, said pad comprising: 
 a. a polyurethane urea-containing polishing layer, said polishing layer comprising at least partially gas-filled cells, said polishing layer formed by reaction of polyisocyanate and polyurethane prepolymer, amine-containing material, blowing agent, and optionally hydroxyl-containing material, wherein an opening is formed in said polishing layer; and    b. a second layer wherein at least a portion of said second layer comprises an at least partially transparent window,    wherein said polishing layer is at least partially connected to said second layer, and said opening in said polishing layer at least partially aligns with said window of said second layer.    
     
     
         5 . The pad of  claim 1 , wherein said polishing layer is formed by reaction of hydroxyl-containing material, amine-containing material, blowing agent and at least one material selected from the group consisting of polyisocyanate, polyurethane prepolymer and mixtures thereof.  
     
     
         6 . The pad of  claim 1 , wherein gas in at least a portion of said at least partially gas-filled cells is exposed when at least a portion of a work surface of said pad is at least partially worn away when said work surface is in contact with a substrate to be polished.  
     
     
         7 . The pad of  claim 3  wherein said polyisocyanate has at least two isocyanate functional groups.  
     
     
         8 . The pad of  claim 3  wherein said polyisocyanate is selected from the group consisting of polymeric and C 2 -C 20  linear, branched, cyclic and aromatic polyisocyanates.  
     
     
         9 . The pad of  claim 2  wherein said hydroxyl-containing material is selected from the group consisting of polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, and mixtures thereof.  
     
     
         10 . The pad of  claim 2 , wherein said amine-containing material is selected from the group consisting of aliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines and mixtures thereof.  
     
     
         11 . The pad of  claim 2 , wherein said amine-containing material comprises a polyamine and at least one material selected from the group consisting of polythiol and polyol.  
     
     
         12 . The pad of  claim 2 , wherein said amine-containing material further comprises sulfur.  
     
     
         13 . The pad of  claim 2 , further comprising at least one material selected from urethane catalyst, blowing catalyst, surfactant, and nucleating agent.  
     
     
         14 . The pad of  claim 1  wherein said pad has a work surface and said surface comprises at least one feature selected from the group consisting of channels, grooves and perforations.  
     
     
         15 . The pad of  claim 1  wherein said polyurethane urea comprises abrasive particulate material.  
     
     
         16 . The pad of  claim 15  wherein said abrasive particulate material is distributed substantially uniformly throughout said polyurethane urea.  
     
     
         17 . The pad of  claim 15  wherein said abrasive particulate material is present in an amount of from 5% by weight to less than 70% by weight based on the total weight of the pad.  
     
     
         18 . The pad of  claim 15  wherein said abrasive particulate material has an average particle size of from 0.001 micron to less than 50 microns.  
     
     
         19 . The pad of  claim 15  wherein said abrasive particulate material is silica.  
     
     
         20 . The pad of  claim 1  wherein said second layer is selected from polyolefins, cellulose-based polymers, acrylics, polyesters and co-polyesters, polycarbonates, polyamides, plastics, and combinations thereof.  
     
     
         21 . The pad of  claim 1  wherein said second layer is selected from substantially non-compressible polymers, metallic films and foils, and combinations thereof.  
     
     
         22 . The pad of  claim 1  further comprising a sub-pad layer having an opening formed therein, said sub-pad layer at least partially connected to said second layer, and wherein said opening in said sub-pad layer at least partially aligns with said window of said second layer and said opening in said polishing layer.  
     
     
         23 . The pad of  claim 22  wherein said sub-pad layer is chosen from non-woven fiber mat, woven fiber mat, or combinations thereof.  
     
     
         24 . The pad of  claim 22  wherein said sub-pad layer is chosen from polyurethane impregnated felt, polyurethane urea impregnated felt, or combinations thereof.  
     
     
         25 . The pad of  claim 22  wherein said sub-pad layer is selected from foam sheet containing natural rubbers, synthetic rubbers, thermoplastic elastomers or combinations thereof.  
     
     
         26 . A method of preparing a pad adapted to polish microelectronic substrates, comprising: 
 a. forming a polyurethane urea-containing polishing layer wherein said polyurethane urea comprises at least partially gas-filled cells, and wherein at least a portion of said at least partially gas-filled cells is formed by an in-situ reaction;    b. forming an opening in said polishing layer;    c. forming a second layer which comprises an at least partially transparent window;    d. at least partially aligning said opening in said polishing layer and said window of said second layer; and    e. at least partially connecting said polishing layer and said second layer.    
     
     
         27 . The method of  claim 26  wherein said polishing layer is formed by combining polyisocyanate with hydroxyl-containing material, amine-containing material and blowing agent to produce polyurethane urea wherein at least a portion of said urea contains at least partially gas-filled cells.  
     
     
         28 . The method of  claim 26  wherein said polishing layer is formed by combining polyisocyanate with hydroxyl-containing material to form polyurethane prepolymer; and 
 combining said polyurethane prepolymer with amine-containing material and blowing agent to form polyurethane urea wherein at least a portion of said urea contains at least partially gas-filled cells.    
     
     
         29 . The method of  claim 27  wherein said polishing layer is formed by combining polyisocyanate and polyurethane prepolymer with hydroxyl-containing, amine-containing material and blowing agent to form polyurethane urea wherein at least a portion of said urea contains at least partially gas-filled cells.  
     
     
         30 . The method of  claim 27  wherein ingredients are combined at a pressure of less than 20 bar.  
     
     
         31 . The method of  claim 28  wherein ingredients are combined at a pressure of at least 20 bar.  
     
     
         32 . The method of  claim 26  wherein said at least partially gas-filled cells comprise carbon dioxide.  
     
     
         33 . The method of  claim 26  wherein said at least partially gas-filled cells have an average size of from at least 1 micron to less than 100 microns.  
     
     
         34 . The method of  claim 26  wherein said substantially gas-filled cells are substantially uniformly distributed throughout said polyurethane urea.  
     
     
         35 . The method of  claim 27  wherein said blowing agent comprises water.  
     
     
         36 . The method of  claim 28  wherein said blowing agent is water.  
     
     
         37 . The method of  claim 27  further comprising adding an auxiliary blowing agent.  
     
     
         38 . The method of  claim 28  further comprising combining said polyurethane prepolymer with an auxiliary blowing agent.  
     
     
         39 . The method of  claim 37  wherein said auxiliary blowing agent is selected from the group consisting of acetone, ethyl acetate, and halogen-substituted alkanes.  
     
     
         40 . The method of  claim 38  wherein said auxiliary blowing agent is selected from the group consisting of acetone, ethyl acetate, and halogen-substituted alkanes.  
     
     
         41 . The method of  claim 26  further comprising: 
 a. forming a sub-pad layer wherein an opening is formed therein;    b. at least partially aligning said opening in said sub-pad layer with said window of said second layer and said opening in said polishing layer; and    c. at least partially connecting said sub-pad layer and said second layer.    
     
     
         42 . A pad assembly comprising: 
 a. a polishing layer comprising polyurethane urea wherein at least a portion of said polyurethane urea comprises at least partially gas-filled cells wherein at least a portion of said cells are formed by an in-situ reaction, said polishing layer having a work surface and a back surface;    b. a backing sheet having an upper surface and a lower surface; and    c. an adhesive means interposed between and at least partially connecting said back surface of said polishing layer and an upper surface of said backing sheet, at least a portion of said adhesive means being at least partially transparent,    wherein an opening is formed in each of said polishing layer and said backing sheet, and wherein said openings in each polishing layer and backing sheet are at least partially aligned with said transparent portion of said adhesive means, and wherein said polishing layer is at least partially connected to said adhesive means and said adhesive means is at least partially connected to said backing sheet.    
     
     
         43 . The pad assembly of  claim 42  wherein said polyurethane urea is formed by combining hydroxyl-containing material, amine-containing material, blowing agent and at least one material selected from the group consisting of polyisocyanate, polyurethane prepolymer and mixtures thereof.