| 摘要 |
PROBLEM TO BE SOLVED: To satisfy even contradictory requirements with the same layer by varying the porosity in a porous silicon region in a predictable manner when it is formed in a silicon block thereby varying the porosity over the entire porous silicon layer. SOLUTION: A silicon doped substrate 200 is subjected to anode oxidation to form a porous silicon layer 210. A region of lower porosity is formed at a predetermined current density in an outer layer 210A where an epitaxial layer is grown. Subsequently, a porosity of 30-70% is provided in a region 210B by increasing the current density. Furthermore, a porosity of 60-80% is provided in a region 210C, which is the closet to the substrate 200, by increasing the current density furthermore. Consequently, a high quality epitaxial silicon layer can be grown in the surface layer 210A having a low porosity and the higher porosity in other parts 210B, 210C of the layer can enhance insulation of the circuit and relax interlayer stress. |
