Factors causing deterioration of depth resolution in Auger electron spectroscopy depth profiling of multilayered systems

Abstract

We have investigated the effects of the sputter-induced roughness on the depth resolution Δz and on the interface position zc obtained by Auger electron spectroscopy (AES) depth profiling of a Ni/Cr multilayer and of an AlAs/GaAs superlattice. We also correlated the escape depth λ with Δz and zc. First, the sputter-induced roughness was evaluated by atomic force microscopy (AFM). Second, both Δz and zc were evaluated quantitatively using an error function fitting method of AES, depth profiles. The AFM observation shows that the height distribution of sputter-induced roughness is approximated to first order by a Gaussian distribution and is correlated with the resolution function which depends strongly on the sputter-induced roughness. The precise measured height distribution is, however, somewhat different from the Gaussian distribution. The computational simulation using the error function approximation fitting is in good agreement with experimental results. We also estimated the escape depth λ using the same computational simulation results. The results indicate that the error function approximation fitting is useful to evaluate Δz and zc as a practical method, but anomalies of Δz and zc are discernable at the specific interface. These anomalies are assumed to come from preferential sputtering.