TEM analysis on the structure of bonding pad interface for bondability issue

Transmission Electron Microscopy (TEM), as a main analysis technique, together with Scanning Electron Spectroscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were employed to analyze the morphology and microstructure of Au-Al interface of Gold ball bonding. A special sample preparation method for TEM analysis was devised to overcome peeling issue of Gold bonding ball from the Al pad. There were two kinds of phases identified below the interface crack based on the elemental analysis and the contrast of TEM pictures. Al had been completely consumed to react with Au after 325degC temperature aging for 1000 hours. Near Al-Au interface, Au₄Al phase with cubic lattice was indexed by the selective area diffraction pattern. The final IMC phase formed by Au-Al interfacial reaction in the middle of the ball bond was observed to be different compared to the peripheral region.