Characterization of intermetallic growth of gold ball bonds on aluminum bond pads

Abstract

In this paper the intermetallic growth between gold ball bond and aluminum bond pad are studied. It involves thermal aging at 150 °C and 200 °C for various time intervals. The relationship between electrical resistance and intermetallic growth are investigated. Process decapsulation followed by Field Emission Scanning Electron Microscopy (FESEM) are used to determine the intermetallic coverage, intermetallic thickness and Kirkendall void of gold ball on aluminum bond pad. The quantitative Energy Dispersive X-Ray (EDX) is used to determine intermetallic phase composition. The result shows that the electrical resistance increase rapidly with temperature and time reflecting faster interdiffusion rates. The resistance might increases to infinity without degradation in bond strength. The magnitude of intermetallic growth for Au-Al increases with the increases of thermal aging and temperature. Under thermal aging, the void and separation layer propagates further and easily seen after 1000 hours and 40 hours at 150°C and 200°C respectively.