Polyurethane composition for cmp pads and method of manufacturing same

Abstract

Polyurethane composition based on a certain polyether and polyester prepolymer reaction mixture, wherein the composition is utilized in manufacturing chemical mechanical polishing/planarizing (CMP) pads. The CMP pads have low rebound and can dissipate irregular energy as well as stabilize polishing to yield improved uniformity and less dishing of the substrate.

What is claimed is: 
     
         1 . A polyurethane chemical mechanical polishing pad derived from a polyether/polyester based prepolymer reaction mixture, comprising:
 (a) toluene diisocyanate (TDI)-terminated polytetramethylene ether glycol based prepolymer in an amount of about 60-80 weight percent (wt %) based on the total weight of prepolymer mixture;   (b) toluene diisocyanate (TDI)-terminated ethylene adipate polyester prepolymer in an amount of about 40-20 weight percent (wt %), wherein the weight percent based on the total weight of prepolymer mixture;   (c) an effective amount of surfactant and curative, respectively, and   (d) a foaming agent introduced into the reaction mixture to form said polishing pad, wherein the resulting polishing pad has a density ranging from about 0.6 to about 0.95 g/cc.   
     
     
         2 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the prepolymer reaction mixture is about 65-75 wt % polyether prepolymer to about 25-35 wt % polyester prepolymer. 
     
     
         3 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the prepolymer reaction mixture is about 70 wt % polyether prepolymer to about 30 wt % polyester prepolymer. 
     
     
         4 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the TDI-terminated ethylene adipate polyester has a molecular weight ranging from about 2500 to 4000 and is based on a reaction of an ethylene adipate polyol with a 1,3-diisocyanato methylbenzene. 
     
     
         5 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the average weight percent of unreacted isocyanate group (NCO) present in the prepolymer mixture ranges from about 6.5% to about 8.5%. 
     
     
         6 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the surfactant is selected from the group of silicone and polysiloxane-polyalkyleneoxide surfactants, in an amount from 0.3 to 5.0 wt % of prepolymers and surfactant. 
     
     
         7 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the effective amount of curative is in a ratio of 0.9 to 1.0 to the prepolymers utilized, wherein the ratio corresponds to a combination of amine and hydroxyl groups relative to an amount of available isocyanate groups. 
     
     
         8 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the curative is an aromatic diamine. 
     
     
         9 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the pad has a Bashore rebound in the range of about 20% to about 50%. 
     
     
         10 . The polyurethane chemical mechanical polishing pad of  claim 1 , wherein the pad has a removal rate of a metallic film from a wafer ranging from about 7,400 to about 7,900 Å/min. 
     
     
         11 . A method of making a polyurethane chemical mechanical polishing pad derived from a polyether/polyester based prepolymer reaction mixture, comprising:
 (a) mixing toluene diisocyanate (TDI)-terminated polyether prepolymer in an amount of about 60-80 weight percent (wt %) with toluene diisocyanate (TDI)-terminated polyester prepolymer in an amount of about 40-20 weight percent (wt %), in the presence of an effective amount of surfactant, wherein the weight percent is based on the total weight of the prepolymers;   (b) frothing the reaction mixture of step (a) by introducing a foaming agent into the reaction mixture; and   (c) polymerizing the frothed reaction mixture in the presence of an effective amount of curative to form a polishing pad having a density ranging from about 0.6 to about 0.95 g/cc.   
     
     
         12 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the prepolymer reaction mixture is about 65-75 wt % polyether prepolymer to about 25-35 wt % polyester prepolymer. 
     
     
         13 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the prepolymer reaction mixture is about 70 wt % polyether prepolymer to about 30 wt % polyester prepolymer. 
     
     
         14 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the polyether and polyester prepolymers are first mixed with the surfactant in a tank and the frothing agent is added to said tank to form a froth. 
     
     
         15 . The method of making a polyurethane chemical mechanical polishing pad of  claim 14 , wherein the froth is routed to a mixer tank and curative is added to said mixer tank. 
     
     
         16 . The method of making a polyurethane chemical mechanical polishing pad of  claim 15 , wherein a green cured polyurethane foam is dispensed from said mixer tank and further cured. 
     
     
         17 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the prepolymers, surfactant, and frothing, agent are provided in the same tank, and the curing agent is added thereafter to the same tank. 
     
     
         18 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the TDI-terminated polyester is an ethylene adipate polyester having a molecular weight ranging from about 2000 to 4000 and is based on a reaction of an ethylene adipate polydiol with a 1,3-diisocyanato methylbenzene. 
     
     
         19 . The method of making a polyurethane chemical mechanical polishing pad of  claim 14 , wherein the average weight percent of unreacted isocyanate group (NCO) present in the prepolymer mixture ranges from about 6.5% to about 8.5%. 
     
     
         20 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the surfactant is selected from the group of silicone and polysiloxane-polyalkyleneoxide surfactants, in an amount from 0.3 to 5.0 wt % of prepolymers and surfactant. 
     
     
         21 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the effective amount of curative is in a ratio of 0.9 to 1.0 to the prepolymers utilized, wherein the ratio corresponds to a combination of amine and hydroxyl groups relative to an amount of available isocyanate groups. 
     
     
         22 . The method of making a polyurethane chemical mechanical polishing pad of  claim 11 , wherein the curative is an aromatic diamine. 
     
     
         23 . A CMP polishing pad produced by the method of  claim 11 .