Creep-resistant polishing pad window

摘要

The polishing pad is useful for polishing at least one of magnetic, optical and semiconductor substrates. The polishing pad includes a polishing layer having a polyurethane window. The polyurethane window has a cross-linked structure formed with an aliphatic or cycloaliphatic isocyanate and a polyol in a prepolymer mixture. The prepolymer mixture is reacted with a chain extender having OH or NH2 groups and having an OH or NH2 to unreacted NCO stoichiometry less than 95%. The polyurethane window has 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 90 and an optical double pass transmission of at least 15% at a wavelength of 400 nm for a sample thickness of 1.3 mm.