Sputtering-induced surface roughness of metallic thin films

Abstract

Changes in surface microtopography which often occur during sputter depth profile analysis can significantly affect the measured depth resolution of interfaces. To understand better the importance of this roughening effect on interface analysis, we have correlated measurements of surface roughness obtained while Auger sputter depth profiling thin metallic multilayered systems (Ni/Cr, Ag/Ni and chromium oxide/Cr) with the observed Auger interface widths. The r.m.s. roughness of these surfaces was measured, in situ, using optical total intergrated scattering (TIS) techniques. We find that the surface roughness increases with sputtered depth as well as with the energy of the impacting ions. The TIS measurements of r.m.s. roughness are in good agreement with the interface widths obtained from the Auger depth profiles and with the predictions of a statistical sputtering model (D. Marton and J. Fine, Thin Solid Films, 151 (1987) 433). At elevated temperatures, 373 and 473 K, a slight decrease is observed in the surface roughness of Ag/Ni thin films, probably as a result of surface diffusion; such materials sputtered at yet higher temperatures (576 and 673 K) become rougher, probably because of recrystallization processes.