A model of plasma-based ion implantation around a round hole in a flat plate

We use a two-dimensional hybrid simulation (particle ions and Boltzmann electrons) to study sheath and ion dynamics around a small round hole in a flat, conducting plate following the application of a large, negative voltage pulse, such as might be encountered during plasma-based ion implantation. Results for hole radii of an eighth and half the ion-matrix overlap length and for depths of one, two and four times the radius are reported. For all these cases, it is found that the hole represents a small perturbation to a planar sheath since the sheath width is always greater than the hole radius. Consequently, most of the ions that enter the hole impact on its bottom at near normal angles; only a small fraction impact on the sidewall obliquely.