Quantitative AES depth profiling of a Ge/Si multilayer structure

Abstract

AbstractAuger electron spectroscopy (AES) depth profiling of a Ge/Si multilayer structure with Ge layers of 2.2, 4.3 and 2.2 nm thickness in Si was performed with Ar+ ions of 1.5 and 3 keV energy and at 74° incidence angle to the normal to the surface. The plot of the Ge LMM Auger peak intensity as a function of the sputtering time was analysed quantitatively using the MRI (mixing–roughness–information depth) model. As a result, the optimum MRI parameters w (mixing length), σ (roughness) and λ (here, used as information depth) were found to be 1.7, 0.8 and 1.6 nm, respectively, for 1.5 keV Ar+ bombardment. For an appropriate evaluation of the 3 keV Ar+ data, w had to be increased to 3.0 nm and σ to 1.4 nm, respectively, while λ was kept constant. In the first run, the MRI calculation results could not be fitted optimally to the profiling results, and therefore the assumed in‐depth distribution of Ge had to be changed accordingly. After a few modifications of the latter and of the roughness parameter, an optimized fit was obtained by changing either the thickness of the layers or the average Ge concentration within the layers, or, most favourably, by a combination of both approaches. Comparison with densitometer measurements on transmission electron microscopy images confirm the thicker layer structure. Copyright © 2002 John Wiley & Sons, Ltd.