Plasma processing of metallic cobalt was experimentally investigated with three fluorine-containing gases, CF4–O2, SF6–O2, and NF3 to determine the surface decontamination rate and to examine the reaction mechanism. Results show that the maximum etching rate reaches 17.12 μm/min with NF3 gas at 420°C, while the rates are 2.56 μm/min and 1.14 μm/min with CF4–O2 and SF6–O2 gas, respectively, at the same temperature. AES analysis identified the constituent elements of the reaction products to be oxygen, fluorine, and cobalt, and XPS analysis reveals that the reaction product with all three plasma gases is very likely to be CoF2.