Cause analysis on abnormal defects between metal layers of IGBT dies for power modules

IGBT dies are widely applied in power modules for new energy vehicles at present, and meanwhile, the reliability has been a research emphasis. As addressed in this paper, abnormal defects at the Al-Ni interfaces of IGBT dies resulted in the failure of power modules for new energy vehicles during the power cycling tests. Based on the failure characteristics, a systematical investigation was conducted to explore the root causes of these defects through a series of study methods such as process traceability, characterization analysis and theoretical analysis. At last, the root causes of the failure were determined through the comprehensive analysis. Furthermore, the formation processes of abnormal defects under different states were reverted, and the detailed formation mechanisms were also confirmed from the special separation characteristics at the Al-Ni interface. Besides, the corresponding countermeasures were also proposed according to the conclusions obtained. It was believed that the achievements would help improve the preparation quality of metal layers of IGBT dies and enhance the integral reliability of power modules for new energy vehicles.