VUV-assisted low temperature bonding for organic/inorganic hybrid integration at atmospheric pressure

Hybrid bonding among Cu, Ti, quartz, and polydimethylsiloxane (PDMS) substrate, by using vacuum ultraviolet (VUV) irradiation and vapor-assisted surface modification processes, turned out highly feasible at 150 °C and atmospheric pressure. Such a hybrid bonding will be of practical use in the 3D integrations of flex transparent substrates and interconnection layers, which are often used in the optical and MEMS (Micro Electro Mechanical Systems) packaging. Bridging molecular layers, which are based on metal hydroxide hydrates and hydrophilic functional groups, were prepared by introducing water vapor onto the surfaces modified with VUV irradiation in nitrogen atmosphere. The x-ray photoelectron microcopy (XPS) results showed that the initial contaminant layers were successfully removed and water molecules could be adsorbed easily. Upon heating at 150 °C, all combinations of starting materials were bonded through amorphous bridging layers, where the intermolecular dehydration inside the layers created tight adhesion. The interface between transparent materials enabled considerably low loss of light transmittance of less than 5 % in the wavelength range of 380-960 nm.