Study on a leaf-like bonding pad defect

Pad residue or contaminations will strongly influence the bonding pad quality and potentially lead to further bonding pad corrosions due to chemical or electrochemical reactions. Many papers have reported that fluorine compounds remained on the bonding pads surface after bonding pads etching will easily lead to multiform corrosions on the bonding pads. In this paper, a leaf-like bonding pad defect was studied and characterized by Auger Electron Spectroscopy, Transmission Electron Microscope, Scanning Electron Microscope, Energy Dispersive X-ray Detector and so on. The top view and cross-section morphologies of the bonding pad defect were observed using SEM and TEM. And the elemental composition of the leaf-like bonding pad defect was analyzed by AES and EDX. AES surface analytical results showed that the fluorine concentration on the corroded bonding pad was much higher than that on the good one. EDX results also showed high fluorine concentration at the corroded area. From the Auger depth profiling results, it was found that the alumina at the corroded area of the aluminum bonding pad was much thicker than the normal native alumina, which might influence the bondablity of aluminum bonding pad to the package materials and lead to the potential failure of the devices. TEM cross-section observation further confirm that alumina at the corroded area was more than 80nm.