Direct interconnection of chemical mechanical polishing (CMP)-cu thin films 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, O₂ gas was introduced into the vacuum chamber to prevent moisture-induced generation of thick Cu(OH)₂ layers, which was considered hydrated. Then the surfaces were contacted with each other at atmospheric pressure. 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.