It is becoming important to evaluate silicon self-diffusion with progress of a silicon semiconductor industry. In order to evaluate the self-diffusion of silicon, silicon isotope superlattices (SLs) is the only marker. For this reason, it is important to correctly evaluate a film thickness and a depth distribution of isotope SLs by secondary ionmass spectrometry (SIMS). As for film thickness, it is difficult to estimate the thicknesses correctly if the cycles of SLs are short. In this work, first, we report the determination of the film thickness for short-period SLs using mixing roughness-information (MRI) analysis to SIMS pro. le. Next, the uncertainty of the conventional method to determine the film thicknesses of SLs is determined. It was found that the conventional methods cannot correctly determine the film thickness of short-period-isotope SLs where film thickness differs for every layer. (C) 2008 Elsevier B. V. All rights reserved.