US Patent 7951716 Wafer and method of producing the same

A wafer is produced at a step of polishing a predetermined face of a wafer to flatten the predetermined face while supplying a polishing liquid onto a bonded abrasive cloth, wherein the bonded abrasive cloth comprises a urethane bonding material consisting of a soft segment having a polyfunctional isocyanate and a hard segment having a polyfunctional polyol and having an expansion ratio of 1.1-4 times and silica having an average particle size of 0.2-10 μm and a hydroxy group, and has a given ratio of the hard segment occupied in the urethane bonding material, a given volume ratio of silica and a given Shore D hardness.