| 摘要 |
PURPOSE:To form a surface protection film which is uniform in grain size and stable to a heat treatment as well as has a high resistivity, by applying a heat treatment to a polycrystalline silicon at a specific temperature and in an inert gas. CONSTITUTION:An SiO2 film 4 with a thickness of 1,000Angstrom or larger is formed on the surface of a silicon substrate 1 having a planer semiconductor element with a p type base region 2 and an n type emitter region 2. Then, a polycrystalline silicon 5 with a thickness of 200-400Angstrom is deposited on the film 4 using SiH4, for example, at 620 deg.C by means of a vacuum CVD apparatus. The silicon substrate 1, having the polycrystalline silicon 5 deposited thereon, is heat-treated in an inert gas at a temperature of 900 deg.C for 30min. Thereafter, an SiO2 film 6 with a thickness of 1-2mum is deposited on the polycrystalline silicon 5 by CVD to form a protection film. This protection film is selectively opened. After base, emitter and collector electrodes 8 are formed, a CVD-Si3N4 film is formed on the whole surface. The thus formed protection film has such electrical characteristics that a leakage current is below 1muA under an electric field of 2X10<6>V/cm which is applied in parallel to the surface of he semiconductor substrate. |
