SILICON DIAGRAM AND MANUFACTURE OF SILICON PRESSURE SENSOR

PURPOSE: To form a diaphragm of an arbitrary shape, regardless of crystal orientation, by forming an n+-type diffusion region on a given portion on an upper wall of a substrate, drilling a through hole and exposing a given portion of the N+-type diffusion region after an n-type silicon epitaxial layer is grown, forming a porous silicon layer by an anode reaction, and etching it. CONSTITUTION: Silicon oxide films 2a and 2b are grown on upper and lower side walls of a silicon substrate 1. A diffusion window is opened by photolithography, and an n+-type diffusion region 4 as an impurity source is formed on a given upper sidewall of the silicon substrate 1. After the silicon oxide film layer 2a removed, an n-type silicon epitaxial layer 5 is grown. A hole 11 is drilled in the n-type epitaxial layer 5 in a photoetching method to expose the n+-type diffusion region 4. A porous silicon layer 9 is formed in anode oxidization. In a selective etching step, an air gap 10 is formed. Then, a diaphragm with a desired shape can be obtained. As compared with the situation in which only side etching phenomenon or formation of a rectangular diaphragm can be obtained by the isotropic or anisotropic etching method, the present method enables to form a diaphragm of an arbitrary shape.