HRTEM and X-ray diffraction analysis of Au wire bonding interface in microelectronics packaging

Interfacial microstructures of thermosonic Au wire bonding to an Al pad of die were investigated firstly by high-resolution transmission electron microscopy (HRTEM) and X-ray micro-diffractometer. The equal-thickness interference structures were observed by HRTEM due to diffusion and reaction activated by ultrasonic and thermal at the Au/Al bond interface. And X-ray diffraction results showed that three different interplanar crystal spacings ('d' value) of the interfacial microstructures were 2.2257 , 2.2645 , and 2.1806 respectively from the high intensity of diffraction to the low intensity of diffraction. These indicated that the intermetallic phase AlAu₂ formed within a very short time. It would be helpful to further research wire bonding technology.