A method and system for cleaning collector optics in a light source chamber. In producing, for example, extreme ultraviolet light for lithography, debris such as tungsten can accumulate on optical components near a light source in the light source chamber.
An etchant, such as a fluorine-containing gas, can be introduced into the light source chamber. The etchant is ionized via electrodes to generate free fluorine. The electrodes can be, for example, existing light source chamber components including the optical components. The fluorine can then react with the debris, forming gaseous compounds, which are pumped out of the light source chamber.