Instability of Critical Electric Field in Gate Oxide Film of Heavy Ion Irradiated SiC MOSFETs

The critical electric field (Ecr) of the gate oxide in 4H-Silicon Carbide (SiC) MOSFETs was measured under inversion bias conditions with ion irradiation. The Linear Energy Transfer (LET) dependence of the Ecr at which the gate oxide breakdown occurred in these MOSFETs was evaluated. The linear relationship between the Ecr-1 and LET was observed for SiC MOSFETs. The slope of the LET-1/Ecr for SiC MOSFETs is almost the same that of the LET-1/Ecr lines for SiC MOS capacitors. The Vds dependence of Ecr was also evaluated. The correlation between the direction of electric field of drain-source region and direction of ion incidence affects to instability of Ecr.