NMOS Logic Circuits Using 4H-SiC MOSFETs for High Temperature Applications

Normally-off 4H-SiC MOSFETs are used to build NMOS logic gates intended for high temperature operation. The logic gates are characterized between 25 degrees C and 500 degrees C. Stable gate operation for more than 200h at 400 degrees C in air is demonstrated. The excellent MOS reliability is quantified using I-V curves to dielectric breakdown and constant voltage stress to breakdown at 400 degrees C. Although the effective tunneling barrier height phi(B) for electrons lowers to 2eV at 400 degrees C, the extrapolated lifetime from constant voltage stress to breakdown measurements is longer than 10(5)h at 400 degrees C for typical logic gate operating field strength of 2MV/cm.