Illumination system for an EUV lithography device and facet mirror therefor
The invention relates to an illumination system for an EUV lithography device, comprising: a first facet mirror having facet elements that reflect EUV radiation, and a second facet mirror having facet elements for reflecting the EUV radiation reflected by the first facet mirror onto an illumination field. At least one of the facet elements of the first facet mirror or of the second facet mirror is designed as a diffractive optical element for diffracting the EUV radiation. In particular, at least one of the facet elements of the second facet mirror is designed as a diffractive optical element for illuminating only a part of the illumination field. The invention also relates to an EUV lithography device comprising such an illumination system, and to a facet mirror comprising at least one diffractive facet element.
1. An illumination system, comprising:
a first facet mirror comprising facet elements configured to reflect EUV radiation;
a second facet mirror comprising facet elements configured to: a) reflect the EUV radiation after the EUV radiation reflects from facet elements of the first facet mirror; and b) reflect the EUV radiation onto an illumination field of the illumination system,
wherein:
a first facet element is a diffractive optical element configured to diffract the EUV radiation;
the first facet element is a facet element of the first facet mirror or the second facet mirror;
a second facet element is configured to illuminate only a part of the illumination field;
the second facet element is a facet element of the second facet mirror; and
the illumination system is an EUV lithography illumination system.
2. The illumination system of claim 1 , wherein the part of the illumination field comprises first and second partial regions of the illumination field, and the first partial region is non-contiguous with the second partial region.
3. The illumination system of claim 2 , wherein:
a first plurality of the facet mirrors of the second facet mirror are configured to illuminate the first partial region;
a second plurality of facet elements of the second facet mirror are configured to illuminate the second partial region; and
the first plurality of facet elements of the first facet mirror is different from the second plurality of facet elements of the second facet mirror.
4. The illumination system of claim 3 , wherein:
the facet elements of the first facet mirror are switchable between first and second positions;
in the first position, the facet elements of the first face mirror are configured to reflect the EUV radiation onto the first plurality of facets of the second facet mirror; and
in the second position, the facet elements of the first facet mirror are configured to reflect the EUV radiation onto the second plurality of facets of the second facet mirror.
5. The illumination system of claim 4 , wherein the facet elements of the second facet mirror define a grid arrangement in which facet elements of the first plurality of facet elements alternate with facet elements of the second plurality of facet elements.
6. The illumination system of claim 5 , wherein the first diffractive facet element comprises:
a substrate comprising a profiled surface; and
a multilayer coating supported by the profiled surface, the multilayer coating configured to reflect EUV radiation.
7. The illumination system of claim 2 , wherein:
the facet elements of the first facet mirror are switchable between first and second positions;
in the first position, the facet elements of the first face mirror are configured to reflect the EUV radiation onto a first plurality of facets of the second facet mirror;
in the second position, the facet elements of the first facet mirror are configured to reflect the EUV radiation onto a second plurality of facets of the second facet mirror; and
the first plurality of facet elements of the second face mirror is different from the second plurality of facet elements of the second facet mirror.
8. The illumination system of claim 7 , wherein the facet elements of the second facet mirror define a grid arrangement in which facet elements of the first plurality of facet elements alternate with facet elements of the second plurality of facet elements.
9. The illumination system of claim 2 , wherein the first facet element is a diffractive optical element configured to deflect EUV radiation onto a radiation sensor.
10. The illumination system of claim 2 , wherein at least one of the facet elements comprises a planar surface.
11. The illumination system of claim 2 , wherein the first facet element comprises:
a substrate comprising a profiled surface; and
a multilayer coating supported by the profiled surface, the multilayer coating configured to reflect EUV radiation.
12. The illumination system of claim 11 , wherein the profiled surface comprises a multi-step surface profile.
13. The illumination system of claim 2 , wherein the first facet element comprises a grating structure having a lateral extent of the order of magnitude of a wavelength of the EUV radiation.
14. The illumination system of claim 1 , wherein the first facet element is the same as the second facet element.
15. The illumination system of claim 1 , wherein the first facet element is different from the second facet element.
16. The illumination system of claim 15 , wherein the first facet element is a facet element of the second facet mirror.
17. The illumination system of claim 1 , wherein the first facet element is a facet element of the first facet mirror.
18. The illumination system of claim 1 , wherein the first facet element is configured to deflect EUV radiation onto a radiation sensor.
19. The illumination system of claim 1 , wherein at least one of the facet elements comprises a planar surface.
20. The illumination system of claim 1 , wherein the first diffractive facet element comprises:
a substrate comprising a profiled surface; and
a multilayer coating supported by the profiled surface, the multilayer coating configured to reflect EUV radiation.
21. The illumination system of claim 20 , wherein the profiled surface comprises a multi-step surface profile.
22. The illumination system of claim 1 , wherein the first facet element comprises a grating structure having a lateral extent of the order of magnitude of a wavelength of the EUV radiation.
23. A lithography device, comprising:
an illumination system according to claim 1 ; and
a projection lens,
wherein the lithography device is an EUV lithography device.
24. A method of using an EUV lithography device comprising an illumination system and a projection lens, the method comprising:
using the illumination system to illuminate a portion of a structured object; and
using the projection lens to image at least a portion of the illuminated structured object onto a substrate,
wherein the illumination system comprises an illumination system according to claim 1 .