Experimental investigation of the increase in depth resolution obtained through the use of maximum entropy deconvolution of secondary ion mass spectrometry depth profiles

Abstract

Depth profiling using secondary ion mass spectrometry (SIMS) provides profiles of high sensitivity and depth resolution. To obtain the greatest depth resolution, low energy probes must be employed to minimize the redistribution of the sample. However, there is a lower limit beyond which further reduction in energy causes a decrease in ion and sputter 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 current leading to unrealistically long analysis times. To overcome these problems a deconvolution method may be employed to extract the maximum amount of information from data acquired at a higher energy. In this article we experimentally investigate the extent to which the maximum entropy deconvolution method may enhance the depth resolution, by studying its effect on a sample containing closely spaced delta layers near the conventional SIMS depth resolution limit.