Effect of bob etching time on wire bonding quality

The dependence of wire bond-pull strength on the morphology of the underlying polycrystalline silicon (poly-Si) beneath the bondpad metal is studied using atomic force microscopy (AFM). Statistical analysis shows that the roughness of the poly-Si is correlated with the wire bond-pull strength. The correlation is believed to be due to the effectiveness of thermal dissipation through poly-Si during the wire bonding process. Statistical analysis also shows that the roughness of the poly-Si is correlated to the buffered oxide etch (BOE) etching time before the bondpad metal deposition. In this work it is concluded that the BOE etching time has a significant effect on the wire bonding quality. The roughness parameter that links the BOE etching time to the wire bond-pull strength is found to be the localization factor.