| 摘要 |
PURPOSE:To always form piezoresistors at the planned accurate positions and to reduce the variation of characteristics due to dispersion of the thickness of a wafer by a method wherein an etching-resistant region, which regulates one part of the prescribed form of a diaphragm part, is provided before a process wherein the back surface of a substrate is etched. CONSTITUTION:A planned diaphragm part 12 is surrounded in the main surface of a silicon wafer 10 and a groove 11, which is deeper than the diaphragm part 12, is formed by using a first etching mask 13. Then, the mask 13 is removed and a thermal oxidation is performed on the surface of the wafer 10 for forming an ethcing-resistant region 14 on the whole surface. Moreover, an Si layer 15 is laminated on the surface of the region 14 in a thickness so deep that the groove 11 is completely buried. Then, the layer 15 and the etching region 14 are removed by methods of polishing, etc., and silicon on the surface of the planned disphragm part 12 is made to expose. Moreover, boron is selectively diffused from one surface of the wafer 10, a necessary number of piezoresistor 16 are formed at the planned diaphragm part 12, an etching is performed by using a second etching-resistant mask 18 and the diaphragm part 12 is formed. |
