A New Isolation Technique for SOS/LSI's–Local Buried Oxide Isolation of SOS (LOBOS)–

Abstract

A new self-aligned oxide isolation technique is described which produces high yield SOS/LSI's. The new technique utilizes self-aligned photoetching steps where the photoresist is exposed to ultraviolet light projected through the back surface of the sapphire substrate. This technique enables a thick SiO2 film grown by chemical vapor deposition to be completely buried between the silicon islands, and is called Local Buried Oxide Isolation of SOS (LOBOS). The buried SiO2 film reduces the step height and prevents the diffusion of impurities from the sapphire substrate to the silicon film. These features result in good interconnections and improved device characteristics. The device characteristics of SOS/MOSFET's with LOBOS structures are compared with those of conventional SOS/MOSFET's.