Patent ID: 7718507

Claim:
A method of producing a bonded wafer comprising: bonding a wafer for an active layer ion-implanted with a light element such as hydrogen or helium to a given depth position onto a wafer for a supporting substrate, and thereafter exfoliating the wafer for the active layer at the ion-implanted portion of the given depth position through a heat treatment to leave an active layer on an outer peripheral portion of the wafer for the supporting substrate and then polishing a terrace portion formed on the outer peripheral portion of the wafer for the supporting substrate to remove island-shaped projections fixed on the terrace portion and made from a sagged part of the wafer for the active layer, in which the polishing of the terrace portion of the active layer is carried out with a predetermined fixed grain abrasive cloth while controlling a scattering of terrace width and smoothness of an outer peripheral face of the active layer to a given range and wherein the fixed grain abrasive cloth comprises a cloth and many fixed grains embedded within the cloth, the cloth comprising a urethane bonding material made from a soft segment having a polyfunctional isocyanate and a hard segment having a polyfunctional polyol and having an expansion ratio of 1.1-1.4 times, and the fixed grains comprising silica having an average particle size of 0.2-10 μm and a hydroxy group, and a ratio of the hard segment in the urethane bonding material is 40-60% as a molecular weight ratio and a ratio of silica in the whole of the fixed grain abrasive cloth is 20-70 volume %, and the fixed grain abrasive cloth has a resulting Shore D hardness of between 40 and 100.