Temperature Dependence of Rapid Thermal Annealing of Silicon on Sapphire

Abstract

AbstractThe material improvement of silicon on sapphire by rapid thermal annealing (RTA) is investigated as a function of the maximum temperature during the RTA cycle. Dramatic improvement of the crystalline quality throughout the silicon epilayer occurs for the lowest RTA temperature used (1160°C). The dechanneled fraction at the surface, Xo = 0.033, for the highest temperature anneal, gives bulk-like silicon values. Thus, at the surface, the crystalline quality is like bulk silicon. For the higher temperature anneals, transmission electron microscopy reveals that only a few microtwins extend to the surface. The defect microstructure in the region of the silicon/sapphire interface is substantially reduced. The RTA results in Al autodoping on the order of 1017 cm-3. The strain in the silicon epilayer is the same both before and after the RTA. The defect elimination can be explained in terms of the motion of the incoherent boundaries of the microtwins.