Creep-resistant polishing pad window

1. A polishing pad useful for polishing at least one of magnetic, optical and semiconductor substrates, comprising a polishing layer, the polishing layer having a polyurethane window, the polyurethane window having a cross-linked structure formed by reacting an aliphatic or cycloaliphatic isocyanate and a polyol to form a prepolymer and reacting the prepolymer with a chain extender consisting essentially of diethyl toluene diamine, 3,5-dimethylthio-2,4-toluenediamine and isomers thereof, 3,5-diethyltoluene-2,4-diamine and isomers thereof, 3,5-diethyltoluene-2,6-diamine, 4,4′-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline), 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”), polytetramethyleneoxide-di-p-aminobenzoate, N,N′-dialkyldiamino diphenyl methane, p,p′-methylene dianiline (“MDA”), m-phenylenediamine (“MPDA”), methylene-bis 2-chloroaniline (“MBOCA”), 4,4′-methylene-bis-(2-chloroaniline) (“MOCA”), 4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”), 4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”), 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane, 2,2′,3,3′-tetrachloro diamino diphenylmethane, trimethylene glycol di-p-aminobenzoate, or mixtures thereof, and having an OH or NH 2 to unreacted NCO stoichiometry less than 95%, the polyurethane window having a time dependent strain less than or equal to 0.02% when measured with a constant axial tensile load of 1 kPa at a constant temperature of 60° C. at 140 minutes, a Shore D hardness of 45 to 80 and an optical double pass transmission of at least 15% at a wavelength of 400 nm for a sample thickness of 1.3 mm and wherein the polyurethane window has a partial cured morphology.

2. The polishing pad of claim 1 wherein the polyurethane window is metastable with a negative time dependent strain.

3. The polishing pad of claim 1 wherein the prepolymer includes greater than two isocyanate groups.

4. A polishing pad useful for polishing at least one of magnetic, optical and semiconductor substrates, comprising a polishing layer, the polishing layer having a polyurethane window, the polyurethane window having a cross-linked structure formed by reacting an aliphatic or cycloaliphatic isocyanate and a polyol to form a prepolymer, and reacting the prepolymer with a chain extender consisting essentially of diethyl toluene diamine, 3,5-dimethylthio-2,4-toluenediamine and isomers thereof, 3,5-diethyltoluene-2,4-diamine and isomers thereof, 3,5-diethyltoluene-2,6-diamine, 4,4′-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline), 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”), polytetramethyleneoxide-di-p-aminobenzoate, N,N′-dialkyldiamino diphenyl methane, p,p′-methylene dianiline (“MDA”), m-phenylenediamine (“MPDA”), methylene-bis 2-chloroaniline (“MBOCA”), 4,4′-methylene-bis-(2-chloroaniline) (“MOCA”), 4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”), 4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”), 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane, 2,2′,3,3′-tetrachloro diamino diphenylmethane, trimethylene glycol di-p-aminobenzoate, or mixtures thereof, and having an OH or NH 2 to unreacted NCO stoichiometry less than 90%, the polyurethane window being metastable, the polyurethane window having a negative time dependent strain when measured with a constant axial tensile load of 1 kPa at a constant temperature of 60° C. at 140 minutes, a Shore D hardness of 50 to 80 and an optical double pass transmission of at least 15% at a wavelength of 400 nm for a sample thickness of 1.3 mm and wherein the polyurethane window has a partial cured morphology.

5. The polishing pad of claim 4 wherein the prepolymer includes greater than two isocyanate groups.

6. The polishing pad of claim 4 wherein the polyurethane window has an optical double pass transmission of at least 18%.

7. The polishing pad of claim 4 wherein the polyurethane window has a Shore D hardness of 55 to 75.