EXPERIMENTAL INVESTIGATION OF THE INCREASE IN-DEPTH RESOLUTION OBTAINED THROUGH THE USE OF MAXIMUM-ENTROPY DECONVOLUTION OF SECONDARY-ION MASS-SPECTROMETRY DEPTH PROFILES

Depth profiling using secondary ion mass spectrometry (SIMS) provides profiles of high sensitivity and depth resolution. To obtain the great est depth resolution, low energy probes must be employed to minimize t he redistribution of the sample. However, there is a lower limit beyon d which further reduction in energy causes a decrease in ion and sputt er yields to a point where sensitive SIMS is no longer possible. Also, with most ion guns, a reduction in energy brings a dramatic loss of c urrent leading to unrealistically long analysis times. To overcome the se problems a deconvolution method may be employed to extract the maxi mum amount of information from data acquired at a higher energy. In th is article we experimentally investigate the extent to which the maxim um entropy deconvolution method may enhance the depth resolution, by s tudying its effect on a sample containing closely spaced delta layers near the conventional SIMS depth resolution limit. (C) 1996 American V acuum Society.