Year
2015
Abstract
The physical models are applicable for a wide range of implantation conditions without the need for an additional calibration. This study outlines the fundamental physics associated with the penetration of energetic ions into solids. The moving ions lose energy to the solid, create point defects, and after stopping they produce the final distribution in the target. The Monte Carlo modelling of ion implantation allows the incorporation of arbitrarily complex physical models at an atomic level. The electronic stopping power of the target is complicated and not fully understood up to now, since several physical processes contribute to the electronic energy loss: i) Direct kinetic energy transfer to target electrons, mainly due to electron-electron collisions. ii) Excitation of band- or conduction-electrons (effect on weakly bound or non-localized target electrons). iii) Excitation or ionization of target atoms (effect on localized electrons). iv) Excitation, ionization, or electron-capture of the projectile. The core of the simulator performs the calculation of ion trajectories in a three-dimensional manner independent of the dimension of the simulated device structure. An ion trajectory is simulated by successively applying nuclear and electronic stopping processes that slow down the ion motion. Therefore it is necessary to locate atomic nuclei of the target which collide with the ion projectile. After finding the location of the next collision partner, the parameters of the nuclear and electronic stopping models are determined. The partner dependent parameters for the stopping models are the mass and charge of the target atom, the impact parameter, and the free flight path length between two nuclear collisions. Several physical and numerical models are involved in the trajectory calculation. Each material segment of the simulation domain has assigned its own set of models. We have used Monte Carlo implantation on nuclear materials with MCIMPL-II.