Failure mechanism analysis of off-state drain-to-source leakage current failure of a commercial 650V discrete GaN-on-Si HEMT power device by accelerated power cycling test

A gallium nitride on silicon substrate (GaN-on-Si) high-electron-mobility transistor (HEMT) power device is commercially available. The package-level reliability of a GaN-based power device is necessary to respond market demands. Power cycling (PC) tests are a useful method to investigate the reliability of a packaged power component closer to a real application. An off-state drain-to-source leakage current failure (IDSS) of a 650. V discrete GaN-on-Si power device under PC test was reported in a previous study. In this paper, to investigate failure mechanism from the last study experiments to verify the root cause are conducted. Scanning acoustic microscope (SAM) images of failure samples exhibit the solder delamination between the discrete chip and the lead frame. The reasonable hypothesis of a correlation between the delamination and IDSS failure is suggested and is tested with a detailed analysis and supplemental experiments. In the process of analyzing the above hypothesis, the new risk of IDSS failure caused by losing electrical connection of silicon substrate rises. The solution for the risk also is proposed. It is discussed that the IDSS failure phenomenon is related to thermal stress induced during PC test. The tests and the analysis indicate that the failure is a thermal stress induced IDSS leakage, not matched previously reported mechanisms.