Explore High Bonding Reliability of Cu Wire Bonded Devices under Extreme Halide Contaminated Environments

Abstract

Abstract Copper has rapidly replaced gold as the preferred wire bonding material in microelectronic packaging due to its lower cost and many performance advantages. However, halides induced corrosion-related failures need to be carefully controlled to ensure maximum bonding reliability. Literature reported corrosion studies mostly focus on intermetallic compounds as the corrosion vulnerability. Utilizing a novel corrosion screening approach, we established that the bimetallic contact between Cu balls and Al bond pad is the real driver for the observed heavy Al pad corrosion induced by chloride ions [1]. We identified, for the first time, H2 evolution was the coupling cathodic half reaction to the Al bond pad corrosion. With these improved mechanistic insights, we developed an effective corrosion inhibition strategy that utilizes chemical vapor deposition to selectively bond corrosion inhibitors to these critical Cu ball/Al pad interfaces. A new corrosion-screening platform was developed to evaluate the effectiveness of this inhibitor protection treatment. After intentionally loaded chloride contaminants on the die surface, the molded Cu wire bonded devices with selected inhibitor treatment were subjected to PCT stress tests. The subsequent failure analyses, showed selected inhibitor treatment is highly effective of preventing Al bond pad corrosion even under the massive attack of heavy Cl− ion contamination and extensive delamination.