| 摘要 |
<p>PURPOSE:To obtain a flow sensor which has a thin film heater isolated thermally and electrically from the side of a substrate to generate no vortex in a gas flow. CONSTITUTION:A single crystal single layer 2 with an additive of a high concentration of boron is formed on the surface of an n-type silicon substrate 1. SiO2 films 4 and 5 are formed on both sides of the substrate by thermal oxidation and a window is opened in the SiO2 film 5 on the rear thereof. As a result, when the substrate 1 undergoes an anisotropic etching, a cavity 15 is made in the n-type silicon substrate 1 while the single crystal silicon layer 2 with the additive of the high concentration of boron will not be affected by the anisotropic etchant, hence being left on the cavity 15 in a diaphragm. The product thus obtained is utilized as a thin film heater 6. Electrodes 7 and 7 are arranged on the upstream and downstream sides so that current flows through the thin film heater 6 along the flow of a gas. A slit 8 is formed in the SiO2 film 4 on a groove 3 on the upstream and downstream sides of the thin film heater 6 to isolate the thin film heater 6 thermally and electrically from the substrate 1. Temperature sensors 9 a, b and c are arranged on the thin film heater on the upstream side, at the center and on the downstream side respectively along the flow of the gas.</p> |
