Adhesion enhancement of magnetron-sputtered copper films by ion bombardment etching treatment of nickel and Inconel substrates: investigations by Auger electron spectroscopy and secondary ion mass spectroscopy of the ion beam effects

Abstract Earlier the effects of ion bombardment etching of substrate surfaces on the adhesion strength of sputtered copper films deposited onto nickel and Inconel samples were studied using the scratch adhesion test. It was found that the mean critical load was very low unless the layer produced by mechanical polishing on the substrate surface was eliminated. After elimination of this layer, the mean critical load increased with increasing ion bombardment etching time, and for a sufficiently long ion bombardment etching, it became so high that it was impossible to observe evidence of an adhesion failure. In order to understand the origin of the mean critical load enhancement, observations were made by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The results obtained showed that the mechanism of the adhesion strength enhancement was likely to be complex. However, it was suggested that the major part of the effect came from the elimination, by ion etching, of the layer produced by mechanical polishing on the substrate surface and from improved anchoring of the coating to its substrate due to the creation of vacancies and microcavities in the etched substrate. In this paper, we report secondary ion mass spectrometry (SIMS) measurements carried out in order to complement the observations made by AES. The elemental depth profiles obtained by SIMS show that the penetration of the film material into the substrate is clearly greater when the coating is deposited onto an ion beam-etched substrate than onto a mechanically polished one. It is again considered that this enhanced penetration improves the anchoring of the coating to its substrate and is promoted by the existence of vacancies and microcavities in the etched substrate. Keywords: Sputtered filmsadhesion strengthscratch testAr ion beam etchingAuger electron spectroscopysecondary ion mass spectrometry