Correlation between chip metallization properties and the mechanical stability of heavy Cu wire bonds

Ultrasonic wire-bonding with 300 mm thick Cu wires is carried out on different Cu bond pads on both Si and thermally oxidized Si chips. The hardness of the Cu metallization and the adhesion strength on the substrates is related to the bonding performance and shear test results. Annealing of the chips prior to the bonding process is carried out at different temperatures which significantly reduces the bond pad hardness. Electron-backscatter diffraction results show the corresponding high deformation of Cu pads annealed at 400 °C due to the bonding process.