Crystal-trim and its application to investigations on channeling effects during ion implantation

Abstract

Abstract The formalism for the binary collision code Crystal-TRIM which simulates ion implantation effects in crystalline solids is presented. The treatment of binary collisions, the kinematics and the crystal description are elucidated in detail. The nuclear scattering is described by the ‘universal’ potential. The scattering angles are calculated by semianalytical and analytical formulae. We employ a semiempirical model to describe the electronic stopping of the ions. Thermal vibrations of lattice atoms, the radiation-induced production of vacancies and interstitials and their accumulation, the generation of static lattice disorder due to electronic energy deposition and the influence of a thin amorphous surface layer are considered in the simulation model. The program Crystal-TRIM is applied to calculate range profiles for P+ and B+ implantation into Si at energies between 500 keV and 1 MeV, at ion incidence into axial and planar channels and into ‘random’ directions, and at ion doses between 1013 and 1014 cm−2. A relatively good agreement with experimental data is found if the effects of radiation damage, static lattice disorder and the influence of an amorphous surface layer are taken into account simultaneously. We study dechanneling processes during ion implantation. The dechanneled fraction of the ion beam is calculated in dependence on the depth. Furthermore, we illustrate the motion of individual projectiles within the crystalline solid.