Radiation Response of Negative Gate Biased SiC MOSFETs

Silicon carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFETs) are expected as power electronic devices for high radiative conditions, including nuclear plants and space. Radiation response of commercial-grade prototype SiC MOSFETs with applying the gate bias is of interest, in terms of installation of the device in robots or sensors working under such radioactive circumstances. Due to gamma-rays irradiation, the threshold voltages (Vth) of samples with un- and negative-biased up to −4.5 V slightly shift toward the negative voltage side. In contrast, the positive bias of 2.25 V shifts Vth more negatively. Positive charge densities trapped in the gate oxide of un- and positive-biased samples increased with increasing dose. However, no significant increase was observed for negative-biased samples of −2.25 and −4.5 V. We calculated characteristic parameters for the accumulation of holes in the gate oxide, σpJp which is defined as the product of current density due to holes generated by irradiation and capture cross section for a hole in a trap, and it is lower for these negative biased samples compared with the unbiased case. Application of appropriate negative gate biases to SiC MOSFETs during irradiation suppresses accumulation of positive charges in the gate oxide and negative shift of Vth, due to irradiation

Swelling of radiation-cured polymer precursor powder for silicon carbide by pyrolysis

Ceramic yield, density, volume change and pore size distribution were measured for radiation- and thermally cured PCS powder when they were pyrolyzed in the temperature range of 673–973 K. Higher ceramic yield was obtained for radiation-cured powder due to smaller amount of evolved gas. Temperature dependence of volume change and the total pore volume show that the formation and disappearance of pores in the powders were determined by the volume shrinkage and evolution of decomposed gases. Volume shrinkage narrowed the pore size distribution for radiation-cured powder. For thermally cured powder, the narrowing of size distribution was disturbed by aggregated pores. Smaller amount of evolved gas from radiation-cured powder relative to thermally cured powder prevented the aggregation of pores and provided the narrow size distribution

Membrane-supported LSI with integrated heater and temperature monitor for on-site annealing-recovery from 20 kGy gamma ray irradiation damage

In this study, we proposed a novel membrane-supported large-scale integration (LSI) with integrated heater and temperature monitor for on-site annealing-recovery from TID (total ionizing dose) effect with low energy consumption, aiming at solving the problem of integrated circuit (IC) damage by gamma ray irradiation. The heater and membrane structure were fabricated around an LSI by using MEMS (micro electromechanical systems) technology. The thermal characteristics of the microheater was studied for temperature monitoring to ensure an appropriate recovery temperature. 20 kGy gamma-ray irradiation was performed on the LSI samples and then the irradiated samples were annealed for recovery by the integrated microheater. It was found that the driving current of the LSI decreased after irradiation and almost recovered to the original level after 15-minutes annealing at 300°C. We report, for the first time, the successful recovery of the LSI from 20 kGy gamma-ray TID damage by using the integrated heater and temperature monitor