METHOD OF OPERATING A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS AND PROJECTION OBJECTIVE OF SUCH AN APPARATUS

摘要

A projection objective of a microlithographic projection ex- posure apparatus (10) has a wavefront correction device (42) comprising a first refractive optical element (44) and a sec¬ ond refractive optical element (54). The first refractive op- tical element comprises a first optical material having, for an operating wavelength of the apparatus, an index of refrac- tion that decreases with increasing temperature. The second refractive optical element comprises a second optical mate¬ rial having, for an operating wavelength of the apparatus, an index of refraction that increases with increasing tempera- ture. In a correction mode of the correction device (42), a first heating device (46; 146) produces a non-uniform and variable first temperature distribution in the first optical material, and a second heating device (56; 156) produces a non-uniform and variable second temperature distribution in the second optical material.