Yuanzineng kexue jishu (Apr 2022)
Static and Dynamic Radiation Damage of Silicon Carbide VDMOS and Their Comparison
Abstract
The dynamic characteristics of silicon carbide VDMOS (SiC VDMOS) with different bias states under total dose radiation environment were studied. The effects of 60Co γ�ray irradiation on the threshold voltage and switching characteristics of SiC VDMOS with three bias states were compared. The maximum cumulative dose was 100 krad(Si). When the cumulative dose reached 10, 30, 50, 70, and 100 krad(Si), the sensitive parameters were tested by shift test. Annealing at room temperature for 168 h was carried out, and the annealing changes of the three biases were compared. The device used in the experiment was 39 A and 650 V (SCT3060ALHRC11) N�channel SiC VDMOS produced by ROHM Company. The irradiation experiment was carried out in Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. The irradiation source is 60Co, and the dose rate is 50 rad(Si)/s. The sample was irradiated to 100 krad(Si) at room temperature with different biases (Vgs=-5, 0, 20 V, drain and source grounded). Keithley 4200A�SCS semiconductor characteristic analysis system, BC3193 semiconductor discrete device test system, and self�built dynamic test system were selected on the test instrument. The results show that with the increase of 60Co γ�ray irradiation dose, the trapped charge accumulates in the oxide layer, resulting in the decrease of threshold voltage in the static characteristic. Gate oxides in the device accumulate positively charged oxide trap charges. These positively charged defects attract electrons on the semiconductor surface and increase the surface electron concentration, thus reducing the RDS(ON). There are no notable changes in RDS(ON). At the same time, the total ionizing dose radiation does not affect the IGSS, which is consistent with the results of previous studies. It is worth noting that irradiation can shorten the turn�on time slightly, increase turn�off time increases sharply, and the switching loss increases. For this phenomenon, we believe that the change of depletion layer thickness and threshold voltage after irradiation is the main reason for the differential degradation of its turn�on and turn�off response. On the one hand, due to the delay of the Miller platform region, the gate capacitor is charging and discharging during the device’s opening, and the closing process will be slower. The turn�on and turn�off response of the device will be slower and will be prolonged. On the other hand, the reduction of the threshold often makes the channel region of the device enter the anti�pattern region in advance, which makes the device turn on and turn off in advance faster. Further in�depth and detailed research on dynamic radiation damage characteristics is of great significance to ensure the reliability of SiC power devices in a space radiation environment.
