Investigation on the degradation indicators of short-circuit tests in 1.2 kV SiC MOSFET power modules

Abstract

This paper provides a comprehensive investigation on both static characteristics and short-circuit performance of 1.2 kV SiC MOSFET power modules with 2 nd generation planar technology. The experimental approach is based on the static characteristics measurements and the short-circuit tests with gradual increase of pulse time duration. If any variation of the static characteristics appears, the time duration of next short-circuit tests would keep the same with the last pulse duration (approach 1) or increase continuously (approach 2). The results of the short-circuit waveforms show a gate degradation which is further confirmed with the measurement of the gate leakage current. Additionally, other degradation indicators, including positive shift of threshold voltage, drain leakage current and on-state resistance increase are evidenced and discussed in this paper. These can be used for early prediction of the degradation and failure in the short-circuit conditions.

Review of Methodologies for Evaluating Short-Circuit Robustness and Reliability of SiC Power MOSFETs

“…For example, one such optimized NDT, with minimized stay inductance and capable of sustaining a voltage of up to 10 kV, has been built [32]. Another NDT in [44] for testing 1.2 kV SiC MOSFETs has a significantly smaller stray inductance achieved by very closely placed busbars carrying currents flowing in opposite directions [45]. Apart from that, techniques helpful towards reducing measurement errors due to parasitic parameters must be adopted.…”

“…Under laboratory conditions, the online measurement method can be implemented by placing two voltage probes on each end of the external gate resistance RG. The voltage measured can then be divided by RG to give IGSS [44]. In order to more accurately measure the waveform of IGSS, the RG value is generally selected as tens of ohms [44], [50], [77].…”

“…The voltage measured can then be divided by RG to give IGSS [44]. In order to more accurately measure the waveform of IGSS, the RG value is generally selected as tens of ohms [44], [50], [77]. On the other hand, many research efforts have been devoted to realizing condition monitoring based on IGSS, which can be embedded into commercial gate drivers [64]- [66].…”

“…Moreover, many research efforts have been devoted to investigating SiC MOSFET power modules [44], [79], [80], [81], [82]. Although the short-circuit failure mechanism and the degradation of electrical parameters of power modules have been found out to be consistent with that of discrete SiC MOSFETs [44], [80], [81], in some cases, only a few chips fail, which may be due to non-uniform thermal stress distribution [79], [82].…”

“…Moreover, many research efforts have been devoted to investigating SiC MOSFET power modules [44], [79], [80], [81], [82]. Although the short-circuit failure mechanism and the degradation of electrical parameters of power modules have been found out to be consistent with that of discrete SiC MOSFETs [44], [80], [81], in some cases, only a few chips fail, which may be due to non-uniform thermal stress distribution [79], [82]. It is worth mentioning that, in the study of the SC reliability of 1.2 kV/500 A SiC MOSFET modules in [44], it is found that the significantly increased IGSS after multiple SC cycles has a recovery trend after a few days [44].…”