Nonconventional gas produced from coal

Abstract

Owing to its unique physical and electronic properties, β-SiC is a promising semiconductor material for specialized high temperature, high power and high speed device applications. The development of SiC technology is hindered by the unavailability of good quality, large area β-SiC material. Heteroepitaxial growth of β-SiC on silicon substrates by chemical vapour deposition (CVD) promises to be a cost-effective way of growing large area SiC single crystals. Silicon wafers are cheap and have excellent qualities, and the technology for good wafer surface preconditioning is available. It is well established that ultra-clean process conditions are important for CVD processes. A low pressure CVD apparatus has been developed utilizing state-of-the-art ultraclean system technology. The reactor is an ultrahigh vacuum system that can be loaded with up to eight substrates. The process temperature is limited to the melting point of silicon. The gas supply installation provides excellent gas quality at the point of use. Commercial high purity process gases and point-of-use purification are utilized. Comparative growth studies have been carried out by simultaneously depositing SiC layers on Si(100) and Si(111) substrates. All the relevant process parameters such as temperature, pressure, reaction gas flows, etc. have been varied and investigated. Crystallographic characterization of the CVD-grown SiC films has been carried out. X-ray diffraction measurements reveal 0.08° FWHM (full width at half-maximum) for the SiC(200) rocking curve peak and 0.10° FWHM for the SiC(111) rocking curve peak.