Low temperature bonding of hetero-materials using ambient pressure plasma activation

One critical parameter in wafer level bonding is the process temperature. It should be kept as low as possible. Therefore the reasons are low-melting materials used for vias and different coefficients of thermal expansion (CTE) of bonding partners. In this paper the wafer level bonding of silicon to lithium tantalite (LiTa3) and silicon to glass by using CMP-processes and ambient pressure plasma activation was examined. The bond strength with different bonding, plasma and annealing conditions was characterised by micro chevron test and the razor blade method. Furthermore, the wafer stacks showed after the plasma treatment with different process gases a significant increase of the bonding strength.