Failure analysis for probe mark induced galvanic corrosion and bond degradation during HAST

Understanding the corrosion failure mechanism is vital in designing reliable microelectronic products. We stimulated corrosion on Cu-wired memory device with probe mark damage at the center of Al bond pad. Deep probe marks can trigger pitting corrosion and galvanic corrosion on bond pads in the presence of moisture and corrosive halide ions, resulting in intermetallic deterioration and bond degradation. Strict controls have been implemented to avoid excessively deep probe-mark depth and also to restrict the number of touch-downs during wafer sort testing in order to ensure the strength of the bond pad structure under severe environmental conditions.