Application of laser annealing techniques to increase channel mobility in silicon on sapphire transistors

Abstract

Laser annealing techniques were successfully incorporated into standard metal-oxide-semiconductor silicon-on-sapphrie (MOS/SOS) processing to increase transistor channel mobility. Silicon islands were photolithographically defined and chemically etched (by KOH) on standard SOS wafers. The islands were exposed to radiation from an excimer laser (λ=2490 Å) having a pulse duration of 25 nsec, a beam size in the range 0.1–0.2 cm2, and an energy density in the range 0.5–1.0 J/cm2. Using standard processing techniques, MOS transistors were fabricated and characterized. It was found that MOS transistors fabricated over islands exposed to a beam having an energy density of 0.8 J/cm2 exhibit a 30% increase in channel mobility.