| 摘要 |
PURPOSE:To eliminate the defects generating from the diffusion of impurities by a method wherein, after polycrystalline Si has been provided on an Si surface, impurities are diffused in vapor-phase into the Si. CONSTITUTION:An SiO2 16 of approximately 1mum in thickness is provided in advance on an N type Si wafer 2, and a polycrystalline Si film 36 is deposited on the SiO2 film in a vacuum using SiH4. At this time, the surface of the wafer 2 is contaminated with the swarf 17 of quartz ampoule and the particles 37 wherein diffusion impurities Ga and Si, which is doped in advance, are alloyed. Therefore, after the above has been thoroughly boiled up using aqua regia, it is washed clean with pure water, processed for thirty minutues by the mixed acid of HF+NHO3+H2O, and the swarf 17 and the Ga particles 37 are completely removed together with the polycrystalline Si 36. Accordingly, the front of a P type diffusion layer 22 can be made uniform even after driving. If the predeposition of diffusion impurities is performed at a high temperature for a long time, the density of defects increases, and the density of defects is reduced in proportion to the increase in the thickness of the polycrystalline Si film. Also, the yield rate of an element is improved remarkably when the optimum thickness is selected for the polycrystalline Si film. |
