Ultrahigh Resolution in Sputter Depth Profiling with Auger Electron Spectroscopy Using Ionized SF6 Molecules as Primary Ions

Abstract

Depth profiling studies with Auger electron spectroscopy (AES) on a GaAs/AlAs multilayer structure using different sputtering gases (Ar, Xe, SF6), ion energies of 500, 750 and 1000 eV and ion incidence angles of 70 and 85 deg show that ultrahigh depth resolution with Δz=1.6 nm is obtained for SF6 at 500 eV and 85 deg. Application of the mixing-roughness-information depth (MRI) model for quantitative profile evaluation reveals the various contributions of atomic mixing, roughness and information depth to the depth resolution. Although under optimum conditions the roughness is still predominant with an rms value of 0.7 nm, a record low value of 0.4 nm was found for the mixing zone length. This correponds to less than two monolayers and opens the way to layer-by-layer sputtering without atomic mixing.