Microstructure investigation of Cu/SnAg solid-liquid interdiffusion interconnects by Electron Backscatter Diffraction

The investigation of the grain structure of Cu/SnAg interconnects produced by solid-liquid interdiffusion (SLID) bonding is presented in this study. The texture analysis was carried out using Electron Backscatter Diffraction (EBSD). The samples were manufactured by flux-assisted bonding of two Si dies with an area array of square Cu/SnAg bumps on the bottom die and square Cu bumps on the top die at a temperature of 250°C and bonding time between 35 s and 40 s. The influence of the bonding process carried out under pressure of 1.73 MPa and without pressure on the orientation of the Cu₆Sn₅ grains is shown. The preferred grain orientation of Cu₆Sn₅ is <;0001> parallel to the sample direction [010] (growth direction of the intermetallic compounds (IMCs), perpendicular to Cu surface). This texture decreases with the application of bonding pressure. The Cu grains show the preferred directions <;101> and <;111> parallel to the electroplating direction.