Influence of diffusion on solid-state bonding for micro-bumps at low temperatures

The influence of diffusion on bonding micro-bumps at low temperatures in solid state was studied. The contamination was detected to act as a barrier layer on diffusion during bonding. The diffusion between Au and Sn occurred even at low temperatures by performing surface activation process before bonding and was effective on improving the bonding quality. The increase of bonding strengths of Au-to-Au micro-bumps were slow followed with bonding time, which appeared a logarithmic rate law. 100% bond yield was achieved and the die shear strength was higher than 10 MPa at low temperatures by performing surface activation process before bonding.