JPS6432174A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain a low-cost sensor which allows the thickness of its epitaxial layer to be set freely by using a single crystal substrate having no epitaxial layer and controlling the thickness of a beam through two-stage etching and end point detection by an infrared sensor. CONSTITUTION:The n-type silicon substrate 1 having no epitaxial layer is oxidized thermally to cover the surface with an oxide film 2. Then this oxide film 2 is board, and p-type impurities are implanted only in the holed part to form a gauge resistance diffusion layer 3. Then a nitride film 5 is formed as a final protection film by plasma CVD while a diffusion gate is brought into contact with Al wiring 4. Here, a pad part 10 and an etching part 7 are holed, a silicon etching liquid whose etching speed is not so fast is used first for etching, and the silicone etching liquid is used for etching from the reverse surface. Thus, the two-stage etching is performed and when a hole penetrates a wafer, light from the infrared sensor is absorbed by wax and its reflected light attenuates to enter an off-mode; and thus an end point is detected and the sensor whose initially provided step is held as thick as the beam is obtained.