Failure Analysis on the Abnormal Leakage of the Transistors at Lower Temperatures

Failure location and mechanism analysis of a type of transistors failure are presented in this work. The failure phenomenon of abnormal leakage appeared in the collector terminal at low temperatures test. A series of methods including residual gas analysis (RGA), decapping internal inspection, isolation exclusion test and verification test are adopted to analyze the cause of the failure. Based on scanning electron microscope and energy spectrum analyzer examination, the abnormal leakage between the collector and the base terminal is caused by the multiple factors coupling effect. The effect factors include micro cracks in the passivation layer, the internal moisture and the trace of the movable ion. The formation of micro cracks in the passivation layer lies on abnormal passivation process of the chip. It is beneficial to guide the improvement of process control in foundries. Analysis and test method in this failure case could be useful to the similar failure analysis in the future.