| 摘要 |
PURPOSE:To prevent a substrate from warping by a method wherein the polycrystalline semiconductor layer, which is the body supporting the substrate, is caused to be exposed to the primary surface of the substrate, grooves are provided in the polycrystalline semiconductor layer, the polycrystalline semiconductor inside the grooves are oxidized and the oxide thus formed fills up the grooves. CONSTITUTION:The principal surface of a polycrystalline semiconductor sub strate 1 is locally covered by a mask 7 and then a groove 8 is formed therein. Next, after the removal of the mask 7, a polycrystalline semiconductor thin film 9 with a thickness (t) is provided. Next, the thin film 9 is subjected to oxidation for the formation of a polycrystalline semiconductor oxide film 10. The volume of the resultant oxide film 10 is quantitatively larger than the film 9 before oxidation. The enlargement results in the filling-up of the groove 8. The increase cannot be accomplished with ease because it takes inside the groove 8, which causes some stress to mount inside the groove 8. The stress becomes a pull stress, while counterbalancing the pull stress present in the rear side. As the result, a substrate does not suffer from warpage during a heat treatment process. |
