Failure Analysis of a Degraded 1.2 kV SiC MOSFET after Short Circuit at High Temperature

Abstract

This paper presents the experimental results obtained from investigating the impact of short-circuit in SiC MOSFETs at high temperatures. The results indicate that a gate degradation mechanism occurs under a single-stress short circuit event at nominal voltage and junction temperature of 150 • C. The failure mechanism is the gate breakdown, which can be early detected by monitoring the voltage drop of the gatevoltage waveform. The reduction of the gate voltage indicates that a leakage current flows through the gate, leading to a permanent damage of the device but preserving its voltage blocking capability. This hypothesis has been validated through semiconductor failure analysis by comparing the structure of a fresh and a degraded SiC MOSFET. A Focused Ion Beam cut is performed showing cracks between the poly-silicon gate and aluminium source. Furthermore alterations/particles near the source contact have been found for the degraded device.

Impact of Repetitive Short-Circuit Tests on the Normal Operation of SiC MOSFETs Considering Case Temperature Influence

“…In [10] and [22], the temperature-dependent SC capability and robustness are analyzed, which is limited by the heat-generated leakage current and related to thermal runaway [23]. The gate-oxide damage is also observed by the failure analysis after SC test at 150 ºC [24]. However, the impact of different case temperatures on the SC degrading process still needs to be investigated.…”

SiC tools for reliability study

“…Another method to study SiC-defects consists in using Focus ion Beam (FIB) [7]. In a previous study [3], short circuits were submitted to high temperatures until failure.…”

A Behavior Model of SiC DMOSFET Considering Thermal-Runaway Failures in Short-Circuit and Avalanche Breakdown Faults

“…In the past few years, plenty of researchers have focused on SiC DMOSFET's failures in short-circuit faults. Most of them reach an agreement that there are two failure modes in SiC DMOSFET's short-circuit fault: thermal runaway and gate oxide breakdown [7,9,[25][26][27][28][29][30][31][32][33][34][35][36][37]. As for the origin of thermal runaway failure, there are several different explanations.…”