| 摘要 |
PURPOSE:To form a polycrystalline semiconductor layer of small pattern conversion difference on a very thin oxide film without causing damage, by a method wherein the horizontal etching rate of the polycrystalline semiconductor is made small as compared with the etching rate in the depth direction by applying selective ion implantation. CONSTITUTION:Resist material 7 is formed only on the upper part of polycrystalline silicon 5 deposited on a semiconductor substrate 1 via a thin oxide film 3. Ion of high dosage is implanted in the polycrystalline silicon 5 to be eliminated. As the result of this ion implantation, the polycrystalline silicon 5 to be etched is damaged by the shock of ion, and a damaged layer 9 is formed in the polycrystalline silicon 5. In this state, etching process is performed by using a chemical isotropic dry etching. Thereby, the polycrystalline silicon 6, wherein the resist material 7 is not spread and ion is implanted, is eliminated. After that, the resist material 7 is eliminated, and a desired polycrystalline silicon layer 5 is obtained. By this setup, the etching rate becomes extremely high in the damaged layer, and selective etching in the depth direction is enabled. |
