High-temperature behavior of MOS devices

Bulk-silicon and silicon-on-sapphire (SOS) MOS transistors and CMOS logic gates were characterized at temperatures up to 375 C. The bulk-silicon devices were observed to function only below 300 C; the principal degradation mechanism was found to be current leakage at reverse-biased p-n junctions. SOS devices, whose construction eliminates most of these junctions, showed potentially usable characteristics up to 375 C. However, severe self-heating and significant gate-oxide current leakage were observed in SOS. The fact that recognizable characteristics were observed despite self-heating indicates that SOS devices may be usable at temperatures well above 375 C.