Modified diffusion bond process for chemical mechanical polishing (CMP)-Cu at 150°C in ambient air

This paper describes the feasibility of a low-temperature diffusion bonding process for Cu thin film electrodes in ambient air. After Cu thin film surfaces were bombarded by an Ar fast atom beam in vacuum to remove the initial thick adsorbate layer, the surfaces were contacted with each other at atmospheric pressure. As the exposure condition, O₂ gas with controlled humidity was used to prevent moisture-induced generation of thick Cu(OH)₂ layers, which was considered hydrated. Upon heating at 150degC for 600 s after the touchdown, high bonding strength, which was as high as that of Cu film breakage from the inside, was obtained through a CuO interfacial layer of around 10 nm thickness with considerably low electrical resistivity.