High-temperature silicon-on-insulator electronics for space nuclear power systems: Requirements and feasibility

The authors have performed a study to determine whether silicon very-large-scale integrated circuits (VLSICs) can survive the high temperature (up to 3000C) and total-dose radiation environments (up to 10 Mrad over a 7-10 year system life) projected for a very-high-power space nuclear reactor platform. It is shown that circuits built on bulk epitaxial silicon cannot meet the temperature requirement because of excessive junction leakage currents. However, circuits built on silicon-on-insulator (SOI) material can meet both the radiation and temperature requirements. From a study of interface-trap generation and annealing, they find that one cannot depend on the elevated temperatures of a space nuclear power platform to automatically improve MOS total-dose radiation hardness. Still, at high-enough temperatures (above 1750C for these devices) and long enough times postirradiation, device response can be essentially independent of total dose. Reliability and performance issues are also discussed. They find that the temperature dependence of the threshold voltage of the SOI transistors is less than that of bulk transistors. Moreover, the ''zero-temperature coefficient'' current is much smaller for these ''floating-body'' SOI devices (-- 4 μA) than for bulk devices (-- 60 μA). Survivability of high-temperature SOI VLSICs in space, including immunity to transient and single-event upset (SEU), is also addressed. While a large number of practical issues remain to be resolved, no fundamental barrier against the successful development of VLSICs on SOI for use in very-high-power space nuclear reactor systems has been identified