Improved Offset Voltage Stability of 4H-SiC CMOS Operational Amplifier by Increasing Gamma Irradiation Resistance

We modified the active layout of an operational amplifier (op-amp) to exhibit high gamma irradiation resistance of over 100-kGy using our 4H-SiC complementary MOS technology, which can be applied for measuring instruments installed in nuclear power plants. The op-amp with the modified active layout features both a thin gate oxide and newly developed gate-electrode structure for suppressing the leakage current. From an experiment we conducted, the leakage current of the p-channel MOSFET with modified active layout remained unchanged from the initial value after irradiation, although that of it with the conventional layout we previously evaluated increased by about two orders of magnitude. The offset voltage of the improved op-amp was maintained below 2.8 mV up to 100-kGy irradiation. The improved op-amp also showed a healthy amplification characteristic without distortion.