| 摘要 |
PROBLEM TO BE SOLVED: To prevent a board from being warped by forming a silicon film where an entire film is turned amorphous on the backside an insulating board before a semiconductor device is formed as a light transmission prevention film. SOLUTION: A silicon semiconductor thin film 2 with a thickness of 3,000Åis formed on the surface of a sapphire transparent insulating board 1 by epitaxial growth. Then, the surface of the silicon thin film 2 is oxidized for forming a silicon oxide film 3 with a thickness of 4,000Åbeing used as a surface protection film, and a silicon thin film with a thickness of 200-2,000Åis left. A silicon film 4 with a thickness of 1,000Åis formed on the back surface of the sapphire board 1 by the epitaxial growth. By treating the silicon film 4 by the vapor growth method with SiH4 at a temperature of, for example, 639 deg.C as a feed gas, a thin-film monocrystalline silicon is formed. Silicon 5 is ion-implanted into the silicon film 4 of the back surface of the sapphire board 1, thus forming a light transmission prevention film 41 where the silicon film 4 is turned amorphous state. Then, the silicon oxide film 3 is eliminated, and the silicon thin film 2 is exposed onto the surface.
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