Gate Oxide and Package Reliability of TO-263 SiC MOSFETs

Abstract

This article presents a comprehensive reliability analysis of TO-263 silicon carbide MOSFETs (SiC MOSFETs) from four different vendors, focusing on gate oxide and package degradation. A range of accelerated aging tests (AATs), including positive high-temperature gate bias (PHTGB), negative high-temperature gate bias (NHTGB), high-temperature reverse bias (HTRB), and dc power cycling (DCPC), are conducted to investigate both gate oxide and package reliability. The findings from HTGB and HTRB tests emphasize that even a 10 nm reduction in gate oxide thickness can significantly impact gate oxide reliability compared to similar designs. Furthermore, the results from NHTGB show that the devices are more prone to failure compared to PHTGB, disproving the idea that the device lifetime is longer in the off-state compared to the on-state. The conclusions are drawn from measurements using focused ion beam (FIB) and transmission electron microscopy (TEM), which provide detailed cross-sectional images of the devices. Additionally, the reliability of the TO-263 package is assessed, highlighting solder fatigue failure between the device and the printed circuit board (PCB) as a significant issue. This failure mechanism can lead to the detachment of the device from the PCB, resulting in a loss of connection. The study underscores the importance of optimizing gate oxide thickness and addressing thermal–mechanical stresses to enhance the overall reliability of SiC MOSFETs with TO-263 packages in high-power applications.