CuO thin films produced for improving the adhesion between Cu and Al2O3 foils in a direct bonded copper (DBC) process

Abstract

The direct bonded copper (DBC) process was carried out between Cu and Al2O3 foils and CuO thin films were grown on the surface of Cu foils to reduce the defects produced by the DBC on the surface. CuO thin films were synthesized using a magnetron sputtering system, employing a target of Cu with 99.99% of purity and substrates of Cu foils. The discharge atmosphere for the films growth was (Ar + O2). Once the coatings were grown, coated and uncoated Cu foils were joined at both sides (one on the top and the other at the button) of the alumina foil using the traditional direct bonded process. The Atomic concentration, chemical composition and bonding configuration of both cases were studied by X-ray photoelectron spectroscopy (XPS), finding Metallic Cu, Cu2O and Cu–O bonds; furthermore, the atomic concentration analysis showed that coated Cu foil exhibited lower oxygen percentage, compared with uncoated one. The study of the surface defects was carried out using scanning electron microscopy (SEM) showing that the Al2O3 ceramic was better pasted with the Cu foil including the CuO thin film.