Channeling in manufacturing sharp junctions: a molecular dynamics study

We examine how channeling affects ion implantation depth profiles in silico n and whether channeling can be beneficial for achieving a sharp end-of-ran ge in the profile. Accurate modeling of channeling requires a molecular dyn amics program with a realistic electronic stopping model. We have implement ed the local electronic stopping model originally proposed by Cai et al. an d the Firsov model to describe energy losses in inelastic collisions betwee n recoiling ions and target atoms. Simulations of 0.25-15 keV B and As ions in the [100], [110] [111] and off-channel directions in silicon show that channeling effects become unimportant at keV energies in the [100] and [111 ] directions, whereas in the [110] channel they persist down to the very lo west energies. Implantation into the [100] channel gives optimal sharpness of the profiles down to implantation depths of roughly 400 Angstrom indicat ing that no tilt is necessary for the very shallow implants needed in next- generation semiconductors.