Application of SLAT methodology in bond pad process evaluation for sidewall polymer removal

Abstract

Bond pad sidewall polymer removal in a thick passivation device was attempted using different approaches, longer NE111 clean, 250°C bake and high temperature (HT) NE111 clean. SLAT methodology was adopted to evaluate the Al bond pad quality due to F-content on the bond pad surfaces during long term wafer storage. Both for 250°C bake and HT-NE111 no Fluorine-crystal defects were observed on bond pad surfaces with SLAT studies. However, Cu segregation was noticed, which can cause Al-Cu galvanic corrosion, for 250 °C baking process. But with HT NEU, bond pad sidewall polymers were completely removed and thus, mitigating the risk of F-crystal defect formation. Moreover, this approach was without any other type of defects. This is an alternative approach where EKC solvent is not available to manufacture bond pad surface with no sidewall polymers. Wafers, which were processed with HT NE111 clean, were stored up to 3 months and display no F-crystal on bond pad surfaces.