LITHOGRAPHIC PROJECTION APPARATUS, DEVICE MANUFACTURING METHOD AND DEVICE MANUFACTURING THEREBY

摘要

PROBLEM TO BE SOLVED: To provide an efficient and effective cleaning method of an optical element used in a lithographic projection apparatus without employing any unstable material. SOLUTION: Purge gas containing a small amount of molecular oxygen is supplied from a gas supplying source 4 into a space 2 receiving the optical element 3 used in a lithographic projection apparatus. The optical element is irradiated with a UV radiation beam from a radiation source LA for mask pattern projection or a radiation source 7 exclusive for purge whereby the beam of radiation decomposes oxygen and produces an oxygen radical which cleans the optical element very effectively. When the partial pressure of the molecular oxygen contained in the purge gas is from 1×10-4Pa to 1 Pa, sufficient cleaning can be effected within a short time. According to this method, an unstable material such as ozone or the like is not used whereby an excessive work such as the preparation of the purge gas is not required and the optical element can be cleaned simultaneously with the exposure of the substrate, thereby not requesting the optical element removed from the lithographic apparatus. COPYRIGHT: (C)2003,JPO