A PARTICULARLY FAST TRIM VERSION FOR ION BACKSCATTERING AND HIGH-ENERGY ION-IMPLANTATION

It was an unresolved problem to theoretically treat the details of RBS spectra, e.g. the influence of double or triple scattering events, or the effects of multiple scattering at glancing incidence or exit angles. The same statement holds true for high energy implantation, if more details than just the main peak are of interest, e.g. the lateral or backward low concentration tails which result from large angle scattering. The present work explains the necessary steps to make the TRIM code even more time efficient: (1) consider only large scattering angles individually; (2) account for the remaining small angle collisions in a global way by (a) subtracting the "partial" nuclear energy loss resulting from these small angle collisions, and (b) adding up the multiple scattering angular spreads caused by such small angle deflections; (3) replacing the "magic" procedure by a fully analytic formula of good precision for large angle scattering at high energies (4) modifying the electronic energy loss subtraction to account for the variation of S(e)(E) along the extended free flight paths; and (5) improving the random number generator to provide in a fast way uncorrelated numbers for billions of ion histories without repetition. In some cases it was possible to increase the program speed by an order of magnitude. Examples of backscattering spectra and high energy range profiles are shown, which could not be obtained by previous existing theories or numerical codes within reasonable computing times.