Ionizing radiation tolerance of stacked Si3N4-SiO2 gate insulators for power MOSFETs

The total ionizing dose radiation response of metal-nitride-oxide-semiconductor capacitors are examined. Capacitors with different oxide and nitride thickness combinations are fabricated and irradiated using a Co-60 gamma source. Electrical characterization showed all samples with oxide/nitride stack gate insulators exhibited significantly higher tolerance to irradiation when compared to metal-oxide-semiconductor capacitors. Thick oxide-nitride layers can be used as gate insulators in power metal-oxide-semiconductor field effect transistors. Technology computer-aided design simulations are performed to characterize the radiation effects mechanisms. Spatially distributed interface traps at shallow energy level were present in all the oxide/nitride stacks. These interface traps decrease as total dose increases. This result may be due to radiation induced hydrogen passivation.