Hydrolysis-Tolerant Hybrid Bonding in Ambient Atmosphere for 3D Integration

In this study, a heterogeneous bonding between organic and inorganic materials was realized at low temperature without vacuum atmosphere, by means of the vapor-assisted vacuum ultraviolet (VUV) surface modification method. In this method, an ultrathin bridge layer was created between the surfaces via the VUV irradiation in nitrogen atmosphere containing lower alcohol vapor. The radical species of H, OH, and CH sequentially enabled the initial surface cleaning, partial deoxidization of native oxide, and the formation of hydroxyl-terminated alkyl bridge with multidentate carboxylate on the inorganic material. Due to the dynamic competition of reversible hydrolysis of the multidentate carboxylate, the waterproof characteristic was expected to the bridge layer. The bridge layer was then bonded strongly to the modified organic material surface by hydrogen bond on the moment of contact at room temperature, which was followed by the dehydration condensation upon heating at 423.2 K around. Given polyether ether ketone (PEEK) and wiring metals as the typical materials in the fields of flexible electronics and structural materials, the evolution of chemical surface binding condition was analyzed to optimize the bridge formation. The bond interface showed cohesive fracture after the high humidity storage testing at 358.2 K and RH 85% for 1000 hours. Such the hybrid bonding with ultrathin bridge layer will be of the actual use in 3D flexible integration in near future.