Research on the Short-Circuit Characteristics of Trench-Type SiC Power MOSFETs Under Single and Repetitive Pulse Strikes

Abstract

This paper investigates the short-circuit characteristics of 1.2 kV symmetrical and asymmetrical trench-gate SiC MOSFETs. Based on the self-designed short-circuit test platform, single and repetitive short-circuit tests were carried out to characterize the short-circuit capability of the devices under different electrical stresses through the short-circuit withstanding time (SCWT). Notably, the asymmetric trench structure exhibited a superior short-circuit capability under identical test conditions, achieving a longer SCWT compared to its symmetrical counterpart. Moreover, TCAD was used to model the two devices and fit the short-circuit current waveforms to study the difference in short-circuit characteristics under different conditions. For the degradation of the devices after repetitive short-circuit stresses, repetitive short-circuit pulse experiments were conducted for the two groove structures separately. The asymmetric trench devices show a positive Vth drift, increasing on-resistance, increasing Cgs and Cds, and decreasing Cgd, while the symmetric trench devices show a negative Vth drift, decreasing on-resistance, and inverse variation in capacitance parameters. Both blocking voltages are degraded, but the gate-source leakage current remains low, indicating that the gate oxide has not yet been damaged.

Keywords

• SiC MOSFETs
• trench gate
• short circuit
• degradation