Chemical mechanical polishing pad having a low defect integral window

1. A chemical mechanical polishing pad comprising:

a polishing layer having a polishing surface and an integral window;

wherein the integral window is integrated in the polishing layer;

wherein the integral window is a polyurethane reaction product of a curative agent and an isocyanate-terminated prepolymer polyol;

wherein curative is selected our the group consisting of 4,4′-methylene-bis-o-chloroaniline; 4,4′-methylenc-bis-(3-chloro-2,6-diethylaniline); dimethylthiotoluenediamine; trimethyleneglycol di-p-aminobenzoate; polytetramethyleneoxide di-p-aminobenzoate; polytetramethyleneoxide mono-p-aminobenzoate; polypropyleneoxide di-p-aminobenzoate; polypropyleneoxide mono-p-aminobenzoate; 1,2-bis(2-aminophenylthio)ethane; 4,4′-methylene-bis-aniline; diethyltoluenediamine; 5-tert-butyl-2,4-toluenediamine; 3-tert-butyl-2,6-toluenediamine; 5-tert-amyl-2,4-toluenediamine; 3-tert-amyl-2,6-toluenediamine; chlorotoluenediamine and mixtures thereof;

wherein the isocyanate-terminated prepolymer polyol is a reaction product of a polyol and a polyfunctional aromatic isocyanate;

wherein the polyol is selected from the group consisting of polytetramethylene ether glycol, polypropylene ether glycol, an ester-based polyol, a copolymer thereof and a mixture thereof;

wherein the polyfunctional aromatic isocyanate is selected from the group consisting of 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; 4,4′-diphenylmethane diisocyanate; naphthalene-1,5-diisocyanate; toluidine diisocyanate; para-phenylene diisocyanate; xylylene diisocyanate; and, mixtures thereof;

wherein the curative agent contains curative amine moieties that react with the unreacted NCO moieties contained in the isocyanate-terminated prepolymer polyol to form the integral window;

wherein the curative agent and the isocyanate-terminated prepolymer polyol are provided at an amine moiety to unreacted NCO moiety stoichiometric ratio of 100 to 125%;

wherein the integral window has a porosity of <0.1 vol %;

wherein the integral window exhibits an average compression set of 5 to 25%;

wherein the polishing surface is adapted for polishing a substrate selected from a magnetic substrate, an optical substrate and a semiconductor substrate.

2. The chemical mechanical polishing pad of claim 1 , wherein the integral window has an oval cross section in a plane parallel to the polishing surface.

3. The chemical mechanical polishing pad of claim 1 , wherein the isocyanate-tenninated prepolymer polyol comprises an isocyanate-terminated polytetramethylene ether glycol.

4. The chemical mechanical polishing pad of claim 3 , wherein the isocyanate-terminated polytetramethylene ether glycol contains 9.00 to 9.25 wt % unreacted NCO moieties.

5. The chemical mechanical polishing pad of claim 1 , wherein the isocyanate-terminated prepolymer polyol contains 8.75 to 9.40 wt % unreacted NCO moieties.

6. The chemical mechanical polishing pad of claim 1 , wherein the integral window exhibits an optical transmission of 20 to 50% at 670 nm.