SIMS with low energy (down to 250 eV) primary ions has been widely used for ultra-shallow dopant profiling for ULSI device development. In spite of its high performance in depth resolution, there still remain ambiguities to be overcome in SIMS technique for accurate depth and concentration calibrations in the shallow depth regions. In order to get accurate ultra-shallow boron depth profiles, BN-delta-doped multilayer reference materials were developed and evaluated in a round-robin study using low energy SIMS. Those delta-doped layers were used to measure the sputter rate change in the initial stage of oxygen-ion bombardment. (C) 2004 Elsevier B.V. All rights reserved.