Comparative Analysis of Degradation of SiC MOSFET Power Module With Different Proportions of Al/Cu Buffer Under Power Cycling

Due to the mismatch in coefficient of thermal expansion (CTE) between the SiC chip and the bonding wire, there is a sever thermal-mechanical stress at the bonding interface, causing a significant reduction in the reliability of the bonding wire. By using sintered silver to connect an Al/Cu buffer layer at the top of the chip, the mismatch in CTE between the bonding wire and the chip can be improved, greatly enhancing the reliability of the bonding wire. The integration of the buffer layer with Ag sintering technology significantly improves the reliability of power modules and enhances power density. Furthermore, the buffer layer increases the thermal capacity, thereby reducing the operating temperature of the semiconductor device. In this study, the effects of different Al/Cu stress buffer layers with different proportions on the reliability of the single-sided molded SiC power module with Al bonding wire were investigated through subsecond power cycling tests (PCTs), and the failure modes of the bonding wire were characterized. The results show that the failure point of the bonding wire in the module with an Al/Cu stress buffer layer is located at the cracking of the bonding wire heel. Among the 10-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> m Al/40-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> m Cu buffer layers with good electrical conductivity, the module with this buffer layer has a longer lifetime.