Power Cycling Test Failure Analysis of SiC MOSFET Devices

Abstract

In recent years, gradual development in industry and automobiles and the field of renewable energy production has been achieved led to significant growth in the field of power semiconductors.In particular, operation and non-operation are repeated in such a field, so reliability issues such as delamination and cracking are critical factors.Therefore, there is an increasing demand for reliability verification such as power cycling tests(PCT).In this study, reliability was evaluated using PCT (Mentor Graphics’ Power Tester 1500A), which repeats the heating and cooling of the device by applying continuous gate pulses in the same way as in the actual operating environment.Keysight's B1506A was used to compare the electrical characteristics before and after the PCT.It was found that this increased the turn-on resistance(Ron) on the output curve.The components of the turn-on resistance are:Ron = Rpack + Repi + Rch + R* Where, Rpack is the packaging resistance due to bond wire, metallization, etc., Repi is the drift layer resistor, Rch is the channel resistance, and R* is the other components resistance e.g., the substrate.If there is an increase of Ron, it might be due to Rpack, which is typical power cycling aging [1].We also performed Scanning Electron Microscopy (SEM) analysis for failure analysis and confirmed that the bond wire cracked after PCT.We performed a Scanning Acoustic Microscopy (SAM) analysis for further failure analysis and confirmed that voids were formed in the solder after PCT.Both results are due, as is previously known, to bond wire degradation resulting from thermal-mechanical stress due to the coefficient of thermal expansion (CTE) mismatch between packaging materials [2]. Figure 1