| 摘要 |
PURPOSE:To enable to continuous etching to the final thickness of a diaphragm in a semiconductor pressure sensor by providing a diffused layers of a diaphragms of substantially equal thicknesses from the surface of a semiconductor substrate, and etching to form the diaphragm from the back surface of the substrate while referring to the electric characteristic of the diffused layer. CONSTITUTION:Piezoelectric resistors 2 of the prescribed number are formed on the surface of an N type silicon substrate 1, and double diffused layer 4 of the depth substantially equal to the thickness of the diaphragm to be finally obtained is provided. A current is flowed to a passge 5 between a boundary between the substrate 1 and a P type diffused layer 4a, and a boundary between the N type diffused layer 4b and the P type diffused layer 4a, and the selective etching is performed to form the diaphragm while observing the current value. When the etching level reaches the position of the broken line 7, i.e., in the passage 5, the current value decreases, and when the etching is finished at the time point when the position of the broken line 8, i.e., the passage 5 is completely interrupted and the current becomes substantially zero, the diaphragm of the desired thickness can be formed. |
