Plasma-based ion implantation of a square bar is modeled using a particle-in-cell plasma simulation for three different size bars. When the sheath width is significantly greater than the bar width, it is found that the incident ion dose is largest at the center of the bar and decreases precipitously at the corners. When the sheath width is comparable to the bar width, the incident dose is largest near to, but not at, the corners. It may be possible to optimize dose uniformity by straddling these two regimes. ©1997 American Institute of Physics.