Inorganic Temporary Direct Bonding for Collective Die to Wafer Hybrid Bonding

A newly developed temporary bonding method for die population on a carrier wafer with CVD dielectric film has been demonstrated. With this integration approach, the temporary bonding is done by plasma-activated direct bonding. Therefore, the temporary bonding interface is compatible with most of the front-end processes. Furthermore, the risk of the die sift during bonding can be mitigated since the interface layer is thin and solid state. The key to the temporary bonding is intentional voids formation and acceptably weak adhesion energy by low temperature deposited SiO2 film. The surface roughness, film composition, mechanical property, and impact of plasma activation have been deeply investigated. Furthermore, the interface analysis, e.g. bonding energy measurement at anhydrous atmosphere, interface void inspection, and TEM analysis have been performed. The combination of TDS and positron annihilation spectroscopy (PAS) unveils that the low temperature deposited SiO2 contains a lot of open spaces and water inside the vacancy, which works as a water reservoir, may be released during the post-bond annealing. It eventually forms bonding voids, which works as an initiation of release interface. The CVD SiO2 film interface can be easily released by significantly low force. The alternative temporary bonding technology enable advanced heterogeneous 3D integration, with high yield, high bonding alignment accuracy and cost reduction.