Reliability Characterization of Ion-Induced Leakage Current Degradation in Silicon Carbide Schottky Power Diodes

Abstract

Silicon carbide (SiC) has superior material properties, compared to silicon, for use in high-power electronics, allowing for improved circuit density and efficiency. In space applications, these benefits would improve the proportion of satellite mass and volume that could be devoted towards useful payloads. However, several ion-induced failure modes limit the use of SiC devices in high-radiation environments such as space. Of these failure modes, single-event leakage current increases (SELC) occurs at the lowest voltage biases and therefore determines the limits of the SiC device safe operating area in most situations. In this work, the radiation threshold for SELC is defined for several SiC Schottky diodes spanning several manufacturers and rated breakdown voltages. This threshold appears to be identical for all SiC devices, and modifying an existing model for SELC, the threshold is described as a critical localized power dissipation within an ion strike path. As increased reverse-bias leakage current is not inherently fatal to device operation, but does impact circuit efficiency and reliability, the magnitude and frequency of SELC is also derived from experimental data by forming distributions of step increases in leakage current. The influence of irradiation bias and deposited energy from the ion on both SELC magnitude and frequency is analyzed. Finally, using experimentally-derived SELC distributions, a probabilistic method for estimating cumulative SELC for arbitrary mission lengths and orbits is presented. Decreasing bias voltage appears to decrease SELC significantly across the range of potential outcomes. Increasing device shielding and decreasing mission length reduce the probability of a worst-case cumulative SELC magnitude but do not significantly reduce the worst-case cumulative SELC magnitude. This result suggests SELC is in many instances dominated by a single ion with a high energy transfer, and shielding and mission length alter the probability of such an event occurring.