Simulation on SIMS depth profiling of delta-doped layer including relaxation caused by defects

Using the dynamic Monte Carlo (MC) code, ACAT-DIFFUSE. the SIMS depth profi ling of a multilayered thin film (Ta2O5 (18 nm)/SiO2 (0.5 nm)) sample was i nvestigated. The ACAT-DIFFUSE code is based on the binary collision approxi mation, taking into account the generation of interstitial atoms and vacanc ies, annihilation of vacancies, diffusion of interstitial atoms and primary ions and the relaxation of target materials according to the packing condi tion which include not only beam and target particles but also defects (int erstitial atoms and vacancies). The observed 1-3 nm shift of the delta laye r peak to the surface in SIMS depth profiles can be reproduced by the ACAT- DIFFUSE simulation. It is found that this peak shift is mainly due to the r elaxation or expansion caused by defects produced behind the delta layer, n ot due to the collision mixing which results mainly in broadening the obser ved delta layer peak. Therefore, as ion energy decreases or the angle of in cidence becomes large, the peak shift becomes small, because the total amou nt of defects produced behind the delta layer is small before the delta lay er is sputtered off. (C) 2001 Elsevier Science B.V. All rights reserved.