Investigation of the two-dimensional shape of ion-implanted regions

The two-dimensional shape of arsenic ion-implanted regions in single-crystal silicon was investigated both experimentally and theoretically. Experimentally, two techniques were shown to have the necessary submicron resolution: a junction etch process and an SEM-induced current collection method. A comparison of junction depths determined by the etch technique, the EBIC technique, and spreading resistance with the depths calculated using several amorphous target codes was made. For the case of low temperature (6000C) anneals, the etch technique agrees very well with the junction depths predicted by the amorphous target code due to Winterbon. The lateral junction locations obtained from the etch technique are in good agreement with the predictions of a two-dimensional Monte-Carlo code (TRIM) which indicates that arsenic does not show any significant lateral scattering under mask edges. For the case of high temperature (10000C) anneals, the etch and EBIC techniques agree with each other, but show consistently deeper junction locations than does the spreading resistance technique. Comparison with arsenic-diffusion models shows that concentration-dependent effects are important. Presently available processing models do not appear to adequately forecast junction depths