Development of cosmic ray hardened power MOSFET´s

Developmental power DMOS (double-diffused metal-oxide-semiconductor) FETs were thoroughly characterized in a simulated cosmic-ray environment using heavy ions at the Brookhaven National Laboratory´s tandem Van de Graaff accelerator facility. The primary failure mode encountered on FETs in this environment was susceptibility to single-event burnout. Burnout of the power DMOS FET was catastrophic. Another failure mode was single-event gate rupture. Although gate rupture is not as severe as burnout, its long-term effects are not known. Single-event gate rupture causes performance degradation due to increased gate leakage current. An increase in current can pose serious problems for applications that cannot compensate for the added performance degradation. Long-term reliability of the gate oxide may be affected, resulting in premature device failure. Numerous processing lots were fabricated to verify experimentally that each failure mode could be successfully minimized. Test results have shown that an n-channel, 150-V DMOS FET survived exposures to ions with linear energy transfers up to 80 MeV-cm²/mg. Hardening approaches are discussed, including their advantages and disadvantages in relation to the FET´s performance