Effect of surface treatment on adhesion strength between magnetron sputtered copper thin films and alumina substrate

•Deposition of Cu thin film on Al2O3 substrate is carried out without adhesion layer.•Effectiveness of surface treatments to improve the film adhesion has been evaluated.•Surface roughness and apparent surface energy are two important considerations.•Argon plasma cleaning is the most effective method to improve the adhesion strength.•It works through reducing surface contamination and creating surface dangling bonds. A number of surface pre-treatments have been studied for their effectiveness on the adhesion strength between magnetron sputtered copper (Cu) thin film and polycrystalline alumina (Al2O3) substrate. The treatments include organic solvent cleaning, acid washing, heat treatment, plasma cleaning, and they were organized into different sequences in order to evaluate their individual contribution to the film adhesion. Adhesion strength was measured mechanically using a pull test. By proper pre-treatment, the adhesive strength of at least 34MPa can be achieved with direct sputtering of Cu thin film onto the Al2O3 substrate. With the help of XPS, SEM, XRD, TGA and contact angle measurement, the effect of the different substrate surface treatment techniques has been elucidated.