Arrangement for debris reduction in a radiation source based on a plasma
View Patent ↗The invention is directed to an arrangement for debris reduction in a radiation source based on a plasma, particularly for generating bundled radiation in the extreme ultraviolet (EUV) spectral region. The object of the invention, to find a novel possibility for beam shaping and debris reduction in a radiation source based on a plasma which substantially increases the life of collector optics without having to tolerate a substantial reduction in transparency or a sudden destruction of the protective mechanism, is met according to the invention in that exchangeable additional optics are arranged in the radiation path between a conventional debris filter and the collector optics, wherein a distance-increasing intermediate imaging of the source location relative to the collector optics is provided by the additional optics for further debris reduction.
1. An arrangement for debris reduction in a radiation source based on a plasma comprising:
a radiation-generating plasma as a source location;
collector optics;
a debris filter being arranged next to said radiation-generating plasma and comprising a filter structure having openings which are not covered by foil traps; and
additional optics for forming a distance-increasing intermediate imaging of the source location and provided as a conjugated source location for the collector optics,
wherein additional optics being arranged between the debris filter and the collector optics, and
wherein the additional optics are provided as an auxiliary optical device having at least one reflecting surface to accept residual debris being passed through the debris filter and being exchangeable for restoring reflectivity after defined time periods when reflectivity of the additional optics has reached a defined degree of reduction due to deposition by the residual debris filter during operation of the radiation source.
2. The arrangement according to claim 1 , wherein the additional optics are reflection optics.
3. The arrangement according to claim 2 , wherein the additional optics have reflecting surfaces for reflection in grazing incidence.
4. The arrangement according to claim 3 , wherein the reflecting surfaces of the additional optics are shaped as curved surfaces of revolution.
5. The arrangement according to claim 4 , wherein the reflecting surface has the shape of an ellipsoid of revolution.
6. The arrangement according to claim 4 , wherein the reflecting surface has the shape of a paraboloid of revolution.
7. The arrangement according to claim 4 , wherein the reflecting surface has the shape of a hyperboloid.
8. The arrangement according to claim 4 , wherein the additional optics comprise a combination of a plurality of reflecting surfaces with differently curved surfaces of revolution.
9. The arrangement according to claim 3 , wherein the reflecting surfaces of the additional optics are made of metal which is highly reflective in the EUV region.
10. The arrangement according to claim 9 , wherein the reflecting surfaces of the additional optics are incorporated in highly reflective metallic base material.
11. The arrangement according to claim 9 , wherein the reflecting surfaces of the additional optics are coated with a highly reflective metallic coat.
12. The arrangement according to claim 9 , wherein the reflecting surfaces of the additional optics contain at least one of the metals, molybdenum, rhodium or palladium.