Study of Surface Contamination Produced during High Dose Ion Implantation

Auger ele!tron spectroscopy (AES) was used to examine surface contamination layers on Si produced by high-dose ion implantation. Depth profiling studies indicate that when conventional diffusion pump oil is used in the vacuum system of the implanter target chamber, high-dose implantation of Si exp + or BF sub 2 exp + leads to formation of a carbonaceous surface layer approx 100A thick. Physisorption of hydrocarbons from the implanter residual vacuum followed by radiation-induced polymerization is the most probable cause for the formation of this layer. This layer may account for nonuniform etching characteristics and nonohmic contact formation often observed in heavily implanted Si. Cleaning with organic solvents or peroxide cleaning solution, annealing at 550 deg C for 100 min, and anodic oxidation followed by HF stripping, were evaluated as potential layer removal techniques. Only anodic oxidation with HF stripping was found to be for complete removal of the polymerized layer. The contamination is essentially eliminated by replacing the conventional diffusion pump oil in the target chamber vacuum system with a perfluorinated polyether fluid.21 refs.--AA