| 摘要 |
PURPOSE:To realize stable thermal diffusion by forming a layer including impurity on the impurity diffusion region of semiconductor substrate having one conductivity type, protecting the surface with a silicon nitride film and executing thermal diffusion in the nitrogen gas ambient. CONSTITUTION:The silicon oxide films 17, 18 are formed at the front and rear surfaces in the steam ambient and the poly-silicon films 19, 20 are formed on such silicon oxide films 17, 18. Thereafter, the silicon nitride films 21, 22 are formed in the thickness of 0.1-0.15mum on such poly-silicon films 19, 20. These silicon nitride films 21, 22 are formed, for example, by thermal decomposition of SIH2Cl2 and NH3 by the depressurized CVD method. A semiconductor wafer 23 thus formed is inserted into the diffusion furnace. With such diffusion furnace, a high concentration N type (N<+>) diffusion layer 24 can be formed in the depth of 180mum at the internal surface of N type silicon substrate 11 through the themal diffusion processing at a temperature of 1,270 deg.C for the period of 190hr under the ambient condition of nitride gas (N2) of 4l/min. |
