Gamma-Ray Irradiation Effects on VLSI Geometry MOSFETs Fabricated on Laser Recrystallized SOI Wafers

We have investigated the effects of radiation on the characteristics of NMOS and PMOS FETs having different channel length (1.3μm - 5μm). The FETs were fabricated on SOI wafers where the silicon (0.5μm) film was laser recrystallized. Gammairradiation (up to 200 Krad(Si)) was performed at 300 K while the devices were under bias (+10, 0, -10 volts). Radiation produced severe increases in the NMOS FETs subthreshold leakage currents. Smaller increases with irradiation were observed in the PMOS FET's subthreshold leakage currents. Radiation caused increases in the PMOS FET's threshold voltage with the largest shifts occuring for the +10 volts gate bias. The threshold voltage in NMOS devices decreased with exposure to ionizing irradiation. All the observed threshold shifts are consistent with net hole trapping in the SiO2. We observed a monotonic dependence of the radiation induced threshold voltage shifts on the channel length of PMOS devices. Smaller threshold shifts were obtained for the shorter channel devices.