Research on Total Ionizing Dose Effect of double-trench SiC MOSFET

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In this article, the impact of <sup>60</sup>Co-γ ray irradiation on double trench SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) was investigated under different condiation. First, the effect of the total ionizing dose(TID) on the electrical performance of the device at different gate bias voltages was carried out. The results indicate that at 150 krad (Si) irradiation dose, the threshold voltage of the device after irradiation decreases by 3.28 V and 2.36 V for gate voltages of +5 V and -5 V bias, respectively, whereas the threshold voltage of the device after irradiation decreases by only 1.36 V for a gate voltage of 0 V bias. The threshold voltage of the device after irradiation drifts in the negative direction, and the degradation of the electrical performance is especially obvious under the positive gate bias. This is attributed to the increase in the number of charges trapped in the oxide layer. Meanwhile, room temperature annealing experiments were performed on the irradiated devices for 24, 48 and 168 hours. The shallow oxide trap charges generated by irradiation annealed at room temperature, while the deep oxide trap charges and interface trap charges were difficult to recover at room temperature, resulting in an increase in the threshold voltage of the devices after annealing, indicating that the electrical properties of the devices could be partially recovered after annealing at room temperature. In order to characterise the effect of <sup>60</sup>Co-γ ray irradiation on the interfacial state defect density of the devices, low frequency noise (1/<i>f</i>) tests were performed at different doses and different gate bias voltages. The 1/<i>f</i> low frequency noise test revealed that, under different bias voltages, the presence of oxide trap charges induced inside the oxide layer of the device after irradiation and the interfacial trap charges generated at the SiO<sub>2</sub>/SiC interface increased the irradiated defect density inside the device. This resulted in an increase of 4-9 orders of magnitude in the normalized power spectral density of the drain current noise of the irradiated device.To further obtain the irradiation damage mechanism of the device, a numerical simulation study was carried out using the TCAD simulation tool, and the results revealed that a large number of oxide trap charges induced by irradiation in the oxide layer cause an increase in the electric field strength in the gate oxide layer close to the trench side, which leads to a negative drift of the threshold voltage of the device and affects the performance of the device. The results of this paper can provide important theoretical references for the radiation effect mechanism and radiation reinforcement design of double trench SiC MOSFET devices.