Illumination optical system for projection lithography

摘要

An illumination optical system for projection lithography for the illumination of an illumination field has a facet mirror. An optical system, which follows the illumination optical system, has an object field which can be arranged in the illumination field of the illuminate optical system. The facet mirror has a plurality of facets to reflectively guide part bundles of a bundle of illumination light. Reflection faces of the facets are tiltable in each case. In a first illumination tilt position, the tiltable facets guide the part bundle impinging on them along a first object field illumination channel to the illumination field. In a different illumination tilt position, the tiltable facets guide the part bundle impinging on them along a different object field illumination channel to the illumination field. The reflection faces of the tiltable facets are configured so that the part bundle in the at least two illumination tilt positions is reflected with a degree of reflection R coinciding within a tolerance range of +/−10%. The result is an illumination optical system which avoids an undesired influence of the illumination tilt position of the tiltable facets on the illumination light throughput of the illumination optical system.

主权项

1. An illumination optical system, comprising:
a first facet mirror comprising a plurality of first facets including a group of first facets, each of the first facets having a first reflection face; and a second facet mirror comprising a plurality of second facets, each of the second facets having a second reflection face, wherein:
for each of the first facets of the group of first facets:
when the first facet is in a first position, the first reflection face of the first facet guides a part bundle of illumination light along a first channel to a corresponding second reflection face;when the first facet is in a second position, the first reflection face of the first facet guides the part bundle of illumination light along a second channel to a corresponding second reflection face which is different from the second reflection face to which the first reflection face guides the part bundle of illumination light when the first reflection face is in its first position;when the first facet is in its first position, the first reflection face reflects the part bundle of illumination light with a first reflectivity;when the first facet is in its second position, the first reflection face reflects the part bundle of illumination light with a second reflectivity;the second reflectivity coincides with the first reflectivity within a tolerance range of +/−10%;the corresponding second reflection faces of the first and second channels are located on a conic section portion of the second facet mirror;the conic section portion is limited by a first conic section line and a second conic section line;the first conic section line is defined by a first angle of incidence of the part bundle illumination light onto the first facet;the second conic section line is defined by a second angle of incidence of the part bundle illumination light onto the first facet; andabsolute values of the first angle of incidence and the second angle of incidence differ by at most 10°; andthe illumination optical system is configured to be used for projection lithography.