Influence of ion beam activation on the mode of growth of Cu on Si(100)

Abstract

The influence of simultaneous low-energy argon-ion bombardment on the initial nucleation and growth of sputter-deposited copper on Si(100) under ultrahigh vacuum conditions has been investigated using Auger electron spectroscopy. Argon-ion energies were either 500 or 1000 eV, with the ratio of ion arrival rate to copper atom arrival rate to the substrate ranging from 0.3 to 0.8. Proton-induced x-ray emission was used to measure the thickness (areal density) of the deposited copper. The intensities of the Si-LVV and Cu-LVV Auger transitions were measured as a function of film thickness and from those data it was possible to determine the mode of growth of the copper film. For the case of deposition without ion beam activation, an island growth mechanism was observed. For simultaneous bombardment with 500-eV Ar+ , a complete change to layer-by-layer growth was observed when the ion-to-atom arrival ratio was 0.8. For 1000-eV Ar+ bombardment, the results indicated an island growth mechanism for arrival rate ratios between 0.3 and 0.6, although the possibility of ion beam mixing between the overlayer and substrate, which would affect the interpretation of the data, cannot be discounted. Equilibrium sputtering yields for concurrent ion bombardment and film deposition were also measured and were found to be considerably less than those for equivalent Ar+ bombardment of bulk copper.