QUANTIFICATION OF SECONDARY-ION-MASS SPECTROSCOPY DEPTH PROFILES USING MAXIMUM-ENTROPY DECONVOLUTION WITH A SAMPLE INDEPENDENT RESPONSE FUNCTION

We describe a new method for extracting the secondary-ion-mass spectro scopy response function from measured data for Slayers. The method was developed to reduce the danger of incorporating sample dependent beha vior in the response, and is particularly appropriate for use with sub -keV profile energies where the depth resolution is so high that struc ture can be observed in layers with nm-scale thickness. We demonstrate this method on a system of variously spaced boron delta layers grown in silicon by molecular beam epitaxy. The deconvolved boron distributi ons for different primary ion beam energies, ranging from 500 eV to 6 keV, appear to be self-consistent and the corresponding depth resoluti ons are all increased significantly. Deltas with a 2 nm spacing are re solved without deconvolution using a normally incident 250 eV O-2(+) b eam and the depth resolution (Rayleigh criterion) achievable under the se conditions with deconvolution is <1 nm. Segregation of boron at the near surface side of the delta layers is clearly visible in these dec onvolved data. These features would have been removed using an uncorre cted response. (C) 1998 American Vacuum Society.