A method for operating a semiconductor apparatus includes generating a plurality of target droplets, deforming the target droplets into a plurality of target plumes respectively, changing an orientation of at least one of the target plumes, and generating a plurality of EUV radiations from the target plumes respectively. At least one of the EUV radiations irradiates an area on the light collector different from other EUV radiations in response to the orientation of the at least one of the target plumes.