SIMS analysis of Al δ-doped GaAs test structures using chemical bevelling as a sample preparation technique

A chemical bevelling technique has been developed to synthesize high‐magnification bevels in gallium arsenide for SIMS linescanning and imaging. Bevels have been prepared in gallium arsenide substrate material, in gallium arsenide implanted with aluminium and in two delta‐doped (aluminium) GaAs test structures. The accuracy, sensitivity, dynamic range and depth resolution–depth characteristics of the bevel and linescan approach have been compared to conventional SIMS depth profiling. Images of the bevelled structures have been used to obtain a quick view of the features of interest. Linescans have yielded an aluminium profile from the aluminium implant that is very similar to that from a SIMS depth profile. Linescan results from the aluminium deltas in gallium arsenide indicate that depth resolutions of a few nanometers can be retained to depths of several microns. The depth resolution of the deltas has been measured as a function of bevel magnification and a theory has been developed to explain the results. A peak width (resolution) of 2.2 nm for an aluminium delta has been achieved at a bevel magnification of 6000 using a 15 keV 16O2+ ion beam, and a depth resolution limit of 1.3 nm has been deduced by extrapolation to infinite bevel magnification. The combined effects of beam‐induced mixing, microtopography and the escape depth of the secondary ions is a broadening of 2.0 nm for these conditions.