Patent ID: 8748294

Claim:
A method of preparing a a silicon-on-sapphire (SOS) substrate comprising the steps in the following order of: a) implanting ions into a monocrystalline silicon substrate or a monocrystalline silicon substrate having an oxide film thereon to form an ion-implanted layer therein; b) performing a surface activation treatment on at least one selected from the group consisting of: a surface of a sapphire substrate; a surface of the ion-implanted monocrystalline silicon substrate; or a surface of the ion-implanted monocrystalline silicon substrate having an oxide film thereon; c) bonding the monocrystalline silicon substrate or the monocrystalline silicon substrate having an oxide film thereon and the sapphire substrate to each other at a temperature range of 50° C. to 350° C., and then applying a heat treatment at a temperature range of 150° C. to 350° C. to obtain a bonded body; d) embrittling an interface of the ion-implanted layer of the bonded body by applying visible light irradiation to the bonded body, wherein the embrittling is performed at a temperature range of 50° C. to 350° C. and within the range of 50° C. lower than the temperature of the bonding step to 50° C. higher than the temperature of the bonding step, wherein a laser is used to apply the visible light irradiation and the irradiation energy per unit area is 5 J/cm2 to 30 J/cm2 and the oscillating frequency is 25 mJ@3 kHz at an output of 50 W to 100 W; and e) applying mechanical impact to the interface of the ion-implanted layer to split the bonded body along the interface, thereby transferring the substrate to form a silicon film.