Long-range channelling in low energy ion implantation into silicon

Abstract

Low energy (50 eV) implantation of boron and silicon into crystalline Si through the {110} and {100} faces is studied by a molecular dynamics simulation and the results compared with a binary-collision crystalline computer model and SIMS data. It is found that long-range channelling of the B particles takes place and that their ranges far exceed those predicted by transport theory in random media or Monte-Carlo computer models. It is found that channelling of B occurs only in the 〈110〉 direction. The Si atoms which are displaced by more than the nearest-neighbour spacing always originate from near to the surface as a result of direct knock-ons from ions which do not channel. These displacements show a distinct angular dependence because of the crystalline nature of the solid. For the Si implantation, the attractive forces between the incoming ion and the crystal atoms play an important role in limiting the ion range.