ELIMINATING DOPANT DIFFUSION AFTER ION-IMPLANTATION BY SURFACE ETCHING

Implantation damage is believed to play a significant role in dopant d iffusion. Described here is an attempt to modify the point defect dama ge profile of a 40 keV, Si-29 implant in GaAs by chemically etching aw ay the top 100 angstrom of the sample after implantation. In these sam ples, no Si diffusion was observed after annealing, while significant Si redistribution did occur in a similar sample which received no post -implant etch. TRIM simulations predict an excess Ga vacancy surface l ayer and excess Ga interstitials deeper in the sample. It is thought t hat by removing the vacancy-rich surface layer, the etch alters the im plant damage profile and thus the diffusion behavior of the Si. Surfac e effects from etching as related to the Si diffusion are shown to be consistent with a vacancy-assisted diffusion mechanism. Evidence that this model may be applicable to B implants in Si is also shown.