Gettering process with multi-step annealing and inert ion implantation

Claim 1

A process for producing a semiconductor substrate comprising the steps of: heating a semiconductor substrate material with a first resistivity at a temperature not less than 1100° C. in order to change a major surface of said substrate material into a high resistivity semiconductor layer with a second resistivity higher than said first resistivity, said high resistivity semiconductor layer having resistivity more than 1 ohm cm at a depth of 1.5 um from said major surface of said substrate material, implanting electrically inert impurities into said major surface of said substrate material to produce defect centers in said high resistivity semiconductor layer. heating said substrate material at a temperature ranging from 600° to 900° C. to generate micro defects in both of said substrate material and said high resistivity semiconductor layer, and providing a single crystal semiconductor layer with a third resistivity between said first and second resistivity on said major surface of said substrate material, said third resistivity being larger than said first resistivity.