Patent ID: 8288245

Claim:
A method for manufacturing an SOI substrate, comprising the steps of: providing a damaged semiconductor substrate, wherein the damaged semiconductor substrate comprises: a first damaged semiconductor region in a central portion of the damaged semiconductor substrate; and a step portion in a peripheral portion of the damaged semiconductor substrate, the step portion comprising: a first insulating layer; and a second damaged semiconductor region under the first insulating layer, the second damaged semiconductor region comprising: a semiconductor region under the first insulating layer; and an embrittlement region under the semiconductor region, removing the first insulating layer by a first etching treatment; starting to remove the first damaged semiconductor region and the second damaged semiconductor region by a second etching treatment, stopping the second etching treatment after an etching selectivity of the peripheral portion of the damaged semiconductor substrate to the central portion of the damaged semiconductor substrate per unit time is reduced from two or higher to lower than two, thereby a non-damaged semiconductor region is left, wherein the second etching treatment is performed using a mixed solution, and wherein the mixed solution comprises: a first substance capable of performing an oxidation of a semiconductor material included in the damaged semiconductor substrate; a second substance capable of performing a dissolution of an oxidized semiconductor material; and a third substance capable of controlling a speed of the oxidation of the semiconductor material and a speed of the dissolution of the oxidized semiconductor material; heating the damaged semiconductor substrate under an atmosphere including hydrogen after performing the second etching treatment, thereby a reprocessed semiconductor substrate is manufactured; irradiating the reprocessed semiconductor substrate with ions to form an embrittlement region in the reprocessed semiconductor substrate; bonding the reprocessed semiconductor substrate and a base substrate to each other with a second insulating layer interposed therebetween; and separating the reprocessed semiconductor substrate at the embrittlement region to form a semiconductor layer over the second insulating layer.