Research Disclosure

摘要

This research disclosure relates to an apparatus and method for controlling a pixelated Mirror (Pre-)Heating System (MPHS).The pixelated MHPS may be used in a projection system, for example, in a projection system of an extreme ultraviolet (EUV) lithographic apparatus. Mirrors in such a projection system may be divided into several parts (sectors). To prevent aberrations in a light beam reflected from a mirror, the mirror may be thermally conditioned (i.e. maintained at a desired temperature). The mirror parts have a minimal thermal deformation at a zero crossing temperature T_ZCR. This temperature is above ambient temperature. The pixelated MPHS uses infrared light (IR) to heat the mirror parts to the zero crossing temperature T_ZCR. During EUV exposure of the mirror parts, the pixelated MPHS irradiates the mirror parts with a lower intensity of IR. This balances heat from EUV radiation incident on the mirror to maintain the mirror parts at the (nominal) mirror temperature of T_ZCR.