SOI pressure sensor

Abstract

Abstract A single-crystal silicon piezoresistor has a high sensitivity to strain but has the problem of leakage at the pn junction at elevated temperatures. This usually limits the applications of these devices to less than ≈ 150 °C. This paper presents a technique for fabricating a single-crystal silicon-on-oxide (SOI) pressure sensor for high-temperature applications. The SOI structure is formed from the substrate by a combination of trench etching and anisotropic etching techniques. The desired SOI island is under-etched using an anisotropic etch and then separated from the substrate by an oxidation step. The problems associated with etching convex corners have been avoided by using two trench etchings. The remaining cavities are refilled by polysilicon deposition. By using this technique, a good-quality single crystal can be achieved, without requiring lengthy or expensive processing.