Improving 5V Digital 4H-SiC CMOS ICs for Operating at 400°C Using PMOS Channel Implantation

In this work, the impact of a shallow aluminum channel implantation on the channel properties of SiC p-MOSFETs and digital SiC CMOS devices is investigated. For this purpose, p-MOSFETs, CMOS inverters and ring oscillators with different channel implantation doses were fabricated and electrically characterized. The threshold voltage of the resulting p-MOSFETs was shifted from -5 V to -3.6 V whereas the effective channel mobility was slightly decreased from 11.8 cm²/Vs to 10.2 cm²/Vs for a p-MOSFET channel implantation dose of 2∙1013 cm-2 compared to the non-implanted channel. The resulting p-MOSFETs enable SiC CMOS logic circuits to operate with a 5 V power supply and to satisfy 5 V TTL input level specification over the whole temperature range of 25°C to 400°C. Furthermore the propagation delay time of inverters was reduced by 80% at 25°C and 40% at 400°C compared to inverters without p-MOSFET channel implantation.