A CuCCu Wire-Bonding Enabled by a Cu-Selective Passivation Coating to Enhance Packaging Reliability

Semiconductor device packaging reliability specifications are tightening toward a low ppb to zero defect rate standard due to the increasingly stringent automotive safety requirements. When exposed to chloride ions contamination, the typical copper (Cu) to aluminum (Al) wire-bonding connection could be a potential source of corrosion-related reliability concerns in wire-bonded devices. This article studies the effect of replacing the Al bond pad with Cu on the corrosion-induced lift-off of wire bonds when exposed to low ppm levels of chloride contamination. Real-time immersion corrosion screening was carried out on a wire-bonded device for accelerated time-dependent observation of corrosion progression in 100-ppm chloride solution. The newly developed Cu-Cu wire-bonded devices, enabled by selective passivation to prevent Cu oxidation, dramatically outperformed Cu-Al wire-bonded devices in complete immersion in chloride solution. A chemically discerning reflection-absorption infrared spectroscopy (RAIRS) metrology was used to measure the oxidation suppression provided by a mere few nanometers of passivation coating.