| 摘要 |
A method for manufacturing an SOI substrate superior in film thickness uniformity and resistivity uniformity in a substrate surface of a silicon layer having a film thickness reduced by an etch-back method is provided. After B ions is implanted into a front surface of a single-crystal Si substrate 10 to form a high-concentration boron added p layer 11 having a depth L in the outermost front surface, the single-crystal Si substrate 10 is appressed against a quartz substrate 20 to be bonded at a room temperature. Chemical etching is performed with respect to the single-crystal Si substrate 10 from a back surface thereof to set its thickness to L or below. A heat treatment is carried out with respect to an SOI substrate in a hydrogen containing atmosphere to outwardly diffuse B from the high-concentration boron added p layer 11 , thereby acquiring a boron added p layer 12 having a desired resistance value. During this heat treatment, B in an Si crystal is diffused to the outside of the crystal in a state where it is coupled with hydrogen in the atmosphere, and a B concentration in the high-concentration boron added p layer 11 is reduced. In regard to a heat treatment temperature at this time, in view of a softening point of the insulative substrate, an upper limit of the heat treatment temperature is set to 1250° C., and 700° C. is selected as a lower limit of the temperature at which B can be diffused.
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