Atomic diffusion bonding of wafers with PDC-SiO₂ underlayers using thin Y, Sc, and Zr films

Abstract After quartz glass wafers with PDC-SiO 2 films were bonded using thin Y, Sc, and Zr films, oxidation of these bonded films by oxygen dissociated from the PDC-SiO 2 films was assessed. Optical and structural analyses revealed fully oxidized films formed at the bonded interface, achieved by application of post-bonding annealing at 300 °C using these 0.5 nm thick films. Particularly, Y films were oxidized easily. The surface free energy at the bonded interface γ was evaluated using a blade test, for convenience. The values, found to be higher than 2.6 J m −2 for as-bonded interfaces, were enhanced further by annealing.