CONTRIBUTIONS TO COMPUTER-AIDED INTERPRETATION OF ION SPUTTERING DEPTH PROFILING

To evade some of the problems that restrict the quantification of sput tering depth profiling, i.e. the conversion of measured signal intensi ty vs sputtering time profiles into the concentration vs depth scale i n the case of changing sputtering rate with depth, algorithms and comp uter programs are presented for modelling the intensity vs time profil e by computer simulation of the measuring process. Required are only r ough a priori information on the sample type under investigation, e.g. implanted material or layer systems, some knowledge of the actual spu ttering conditions and basic assumptions on origin, transmission and r egistration of the analytical signals. The modelled profile may be ada pted to the measured one by interactive, stepwise variation of paramet ers assumed to be important. For scanned ion beams, procedures for eff icient estimation of the actual ion current density and of the changin g sputtering rate with depth are given too. All calculations can be pe rformed at a desk using any IBM compatible personal computer. Owing to its modular structure, the program may be easily extended and complet ed according to model refinements by users. Agreement between computed and measured profiles indicates that the a priori assumptions on the true depth profile were correct in all probability. Otherwise, in most cases, further experiments have to be performed in order to decide be tween experimental artefacts and material-inherent deviations consider ing also atomic mixing, radiation enhanced diffusion, preferential spu ttering and similar effects. Moreover, the quantitative relations betw een sputtering conditions and crater shape obtainable by the model can support optimization of the measuring conditions particularly with re spect to depth resolution. At last, the procedures and algorithms give n here are a contribution to the final aim of direct quantification of the results of sputtering depth profiling. This article is an electro nic publication in Spectrochimica Acta Electronica (SAE), the electron ic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by three disks with executable programs, source code files , data files and text files. The manual and tutorial text files includ e material that is useful for learning the effective handling of the p rogram and for program extension by user-written program parts.