<inline-formula> <tex-math notation="LaTeX">${C}_{\textsf{OSS}}$ </tex-math> </inline-formula> Measurements for Superjunction MOSFETs: Limitations and Opportunities

Abstract

Small-signal measurements of output capacitance ( ${C_{\textsf {OSS}}}$ ) are ubiquitous in power semiconductor datasheets and determine critical features of power converters. For silicon superjunction power MOSFETs (SJs), we report ${C_{\textsf {OSS}}}$ measurements with two key anomalies: variation with ac perturbation frequency and hysteresis with dc sweep direction. Using mixed-mode simulations, we attribute the frequency shift to the fundamental SJ structure and find that dc hysteresis is caused by charge trapping from uneven depletion fronts. We show that ${C_{\textsf {OSS}}}$ measurements on SJs do not accurately characterize large-signal operation, underestimating stored energy by up to four times and giving no indication of ${C_{\textsf {OSS}}}$ losses.