Capping a sample surface using amorphous-Si (a-Si) prior to SIMS analysis is a common method for improving ultra-shallow boron depth profiling, however, details of the limitations of a-Si capping have not been thoroughly investigated. In this study we have investigated the problems and/or limitations of a-Si capping method when applied to SIMS. Capping Si layers were grown using Si evaporation in UHV (similar to2 x 10(-8) Pa) at less than 100 degreesC during growth. Using this a-Si capping SIMS method we have successfully measured shallow depth profiles for ultra-shallow B and P. (C) 2004 Elsevier B.V. All rights reserved.