Heteroepitaxial growth of SiC at low temperatures for the application of a pressure sensor using hot-mesh CVD

Abstract

Silicon carbide (SiC) is a wide bandgap semiconductor and it exhibits excellent electronic and chemical properties. Fabrication of SiC devices on Si wafers of large diameter is desired to reduce their production cost. For the fabrication of electronic devices in the SiC layer, however, an electronic isolation between SiC and Si substrate is required because of the leakage current between the SiC and the substrate. Therefore the application of the SOI (Si on insulator) technique to the SiC on insulator (SiCOI) structure has been eagerly investigated [1, 2]. SiCOI structure has been investigated for the applications of piezo-resistive sensors and micro electromechanical systems (MEMS) operating at physically and chemically harsh environments [3]. SiC growth on SOI substrates, however, is very difficult owing to thermal instability of the thin top-Si layer. During the thermal annealing of SOI substrates at the substrate temperature lower than 1000°C depending on the top Si layer thickness, Si atoms agglomerate and the Si islands and voids would be formed [4, 5]. Because outdiffusion of the Si atoms into SiC layer is induced in the case of the SiC growth on Si layer, void formation takes place at lower temperatures than that in the case of the thermal annealing. The SiC growth at much lower temperature than 1000°C, therefore, is required. In our previous study, 3C-SiC epitaxial films were grown at 750°C by hot-mesh CVD, a kind of hot-wire CVD which utilizes the catalytic decomposition of source gases by heated tungsten (W) wires with a mesh structure [6], using monomethylsilane (MMS) as a source gas. In this paper, the epitaxial growth of 3C-SiC films on SOI substrates was investigated by the hot-mesh CVD method. And their piezoresistive property was measured for the application of a pressure sensor.