The development of a dual rate technique for the growth of silicon-on-sapphire films

Abstract

The properties of both p- and n-type 1.5 μm thick silicon on sapphire films can be significantly altered by suppressing the reactions occurring at the silicon-sapphire interface. These reactions can be minimized by using a rapid initial deposition rate (2 μm/min) and a low deposition temperature (1000 °C). The electrical properties of the deposited films can be further enhanced by decreasing the deposition rate to ∼ 0.3 μm/min after surface coverage of the substrate is complete. Both the hole and electron mobilities measured in 1.5 μm thick films grown with the dual rate technique are among the highest yet reported for silicon on sapphire. Films grown with the dual rate technique manifest an increase in the hole concentration during thermal oxidation, in contrast to the decrease usually observed in films grown with existing techniques. This behavior is related to the decreased aluminum content of these films, and also to a possible defect annihilation process that occurs during thermal oxidation. The lowered deposition temperature and the increased initial deposition rate can of course also be used for the growth of films less than 1.5 μm thick.