Effects of doping on polysilicon etch rate in a fluorine-containing plasma

The effects of doping on the polysilicon etch rate in a CF4-CF3Cl-O2 planar plasma reactor are described. The effect is related only to the active carrier concentration and not to the total doping level. No significant change in etch rate was observed for carrier concentrations below 1019 cm−3. At higher concentrations the etch rate rapidly increases for phosphorus and arsenic doping and decreases for boron. A qualitative model, which explains experimental results, is described.