Cu/Ni interface study for bump reliability improvement

Under Bump Metallization (UBM) quality is crucial to the reliability of flip chip products. This paper focuses on the failure mechanism that attributed to Temperature Humidity Bias (THB) test. The importance of metal film condition is emphasized, and the effect of voltage bias is discussed. In addition, a detailed experiment on Cu/Ni UBM interface is carried out for THB improvement. The investigation scope contains Cu surface topography and Cu/Ni interface adhesion. Based on the experiment results, the optimal process condition has been determined. A notable improvement of THB performance is achieved after process optimization.