| 摘要 |
PURPOSE:To form a diffusion layer with good efficiency made of a thin semiconductor substrate, by forming a double layer of a polycrystalline Si layer and Si nitride on one surface of a semiconductor substrate later to pre-diffuse impurity in high density on the other surface followed by slumping. CONSTITUTION:Polycrystalline Si films 12, 12' and sequently Si nitride films 13, 13' with thickness of 0.1mum are formed on the both surfaces of the N type semiconductor substrate 11 with thickness of 250mum by a pressure reducing CVD method to remove the double layer on one surface by etching. The impurity pre- diffused region 14 with high density is formed on the exposed surface of the substrate 11 to depth of approx. 20mum. Subsequently, the remaining double layer is removed by etching. The polycrystalline Si 12' is diffuerent from the substrate 11 in etching characteristic not to cause sagging in the neighborhood of the substrate 11 on ethcing. Lastly, the both surfaces of the substrate 11 are protected by polycrystalline Si 6 and Si nitride film 7 for slumping in a conentional method to form a high inpurity density layer 8. When the multilayer is etching- removed, a semiconductor substrate 18 is obtained. |
