Atomistic simulation of ion irradiation, ion-beam-induced defect formation and defect migration

Ion implantation and subsequent thermal annealing are the standard processes for the electrical doping of semiconductors. Ion implantation is characterized by fast ballistic processes which lead to the deposition of the implanted atoms and to displacements of the target atoms. After the fast relaxation of the displaced atoms a (meta)stable defect structure is formed. Long-term thermally activated processes, especially during thermal annealing, cause defect reduction, rearrangement, and migration. In my talk I will show that computer simulations on the atomic level are a useful tool for the theoretical description of the different physical processes occurring during ion implantation and thermal annealing. The ballistic processes are simulated by the Crystal-TRIM code which is based on the binary collision approximation (BCA). This code is part of different process simulators. Classical molecular dynamics (MD) simulations are employed to investigate defect migration over a period of 10 - 100 ns. The defect diffusivity as well as the microscopic migration mechanisms are studied. A combination of BCA and MD simulations is used to determine the complex defect morphology after the fast relaxation processes are finished. This method allows the effective calculation of the total number and the depth distribution of different defect species (e.g. isolated vacancies and self-interstitials as well as more complex defects) formed on average per incident ion.