Low Temperature Hybrid Bonding of Organic/Inorganic Substrates at Atmospheric Pressure

摘要

Homo- and heterogeneous bonding of Cu, SiO_2, and polyimides, by using a single vapor-assisted surfaceactivation method at 150 °C and atmospheric pressure, is highly feasible and will be of practical use inthree-dimensional hetero-integration of thin, flat interconnection layers where the surfaces of electrodes and insulationlayer appear on the same plane. Since it is necessary to achieve good bondability to diverse materials in a single processin order to obtain such a “bumpless” hybrid structure, we have to create a compatible bridging layer at low temperature.Bridging layers, based on Cu hydroxide hydrate and silanol and hydroxyl groups formed from SiO_2 and a polyimide,respectively, were prepared by introducing water onto the activated surfaces at atmospheric pressure. The growth rate ofthe bridging layers was tunable via absolute humidity, and an exposure of 8 g/m~3 was chosen based on the diffusiondistance of Cu atoms. Heating at 150 °C, after exposure to humidity, caused tight adhesion between the mating surfacesfor all combinations of starting materials with voidless amorphous interfacial (bridging) layers. Because of thewell-controlled layer thickness, a low electrical resistivity of ～ 4 × 10–8 Ω·m was obtained at the Cu-Cu interface.Furthermore, the preliminary study on the surface treatment using ultraviolet irradiation was carried out to Cu andtransparent resin substrate to eliminate the vacuum process.