Illumination unit having a facility for preventing contamination of optical components, and photolithographic apparatus including such an illumination unit
AssigneeASM Lithography B.V.
InventorsJohannes C. H. Mulkens, Nicolaas C. J. A. Van Hijningen, Judocus M. D. Stoeldrayer
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Abstract
An imaging apparatus and an illumination unit for use in such an apparatus are described, which unit comprises an illumination housing (LH) accommodating a radiation source (LA) and at least a reflector (RL). To prevent a decrease of the radiation power supplied by the illumination housing, this housing is provided with means (LA, SH, L.sub.29) which prevent a diffuse deposit of silicon-containing particles present in the ambient air from being formed on optical components within the illumination housing.
Claims6
An illumination unit for illuminating an object with high efficiency in an ambience where particles are decomposed by influence of illumination radiation, said illumination unit comprising:
- (a) an illumination housing,
- (b) a radiation source within said illumination housing,
- (c) an optical system for forming an illumination beam from radiation emitted by said radiation source,
- (d) first means for passing a gaseous cooling medium through said illumination housing to cool said radiation source, and
- (e) second means for preventing deposits of decomposable particles on surface areas within said illumination housing in the path of said illumination beam, said second means being within said illumination housing for preventing said deposits from being formed from gases introduced into said illumination housing, said gases not having been purified of decomposable particles.
Dependencies are inferred from the claim text.