Deconvolution of SIMS Depth Profiles of Boron in Silicon

Abstract

We have measured the depth resolution function of the SIMS analysis of boron in silicon for different experimental conditions and fitted this function with an analytical expression initially proposed by Dowsettet al. We use this analytical depth resolution function for the implementation of an iterative deconvolution algorithm, taking into account several properties of the signal, such as positivity and regularity. This algorithm is described precisely. The algorithm is tested on several theoretical structures and then implemented for the deconvolution of real structures of boron-doped silicon layers in silicon. In particular, a sample constituted by six consecutive delta layers and a 75 A thick layer are deconvolved. It is shown that the asymmetry of the profiles is completely removed and that the full width at half-maximum of the deconvolved delta layers can be reduced down to 41 A. It is also shown that a layer whose real thickness is smaller than the measured width of the resolution function can be easily distinguished from a delta layer, and its thickness estimated.