Lithographic apparatus and device manufacturing method
View Patent ↗A lithographic apparatus is disclosed that includes an optical arrangement having an array of optical elements arranged in a plane perpendicular to the radiation beam. Each optical element comprises an electrical heating device to change an optical path length of the radiation beam. By selectively actuating the electrical heating devices, a position dependent change in optical path length can be achieved in order to correct for irradiation-induced optical path length errors.
1. A lithographic apparatus, comprising:
an illumination system configured to condition a radiation beam according to an intensity distribution;
a support constructed to hold a patterning device, the patterning device configured to impart the conditioned radiation beam with a pattern in its cross-section to form a patterned radiation beam;
a substrate table constructed to hold a substrate;
a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
an array of optical elements arranged transverse to and in a path of the radiation beam, wherein each optical element comprises an individually addressable electrical heating device configured to locally heat the optical element; and
a control unit configured to control the heating devices depending on a phase map of the patterned radiation beam at a pupil plane of the projection system.
2. The lithographic apparatus of claim 1 , wherein the phase map is derived from the intensity distribution.
3. The lithographic apparatus of claim 1 , further comprising an interferometer arranged to measure the phase map.
4. The lithographic apparatus of claim 1 , wherein the control unit is arranged to further control the heating devices depending on a history of previously applied intensity distributions, or a history of applied actuation of the heating devices, or both histories.
5. The lithographic apparatus of claim 1 , wherein at least one optical element of the array of optical elements comprises a channel configured to transport a fluid from a supply container to the at least one optical element so as to establish a static temperature distribution across the at least one optical element.
6. The lithographic apparatus of claim 5 , wherein the control unit is arranged to further control the heating devices depending on a transport velocity and temperature of the fluid.
7. The lithographic apparatus of claim 5 , wherein the channel comprises at least two substantially parallel plates.
8. The lithographic apparatus of claim 7 , wherein the heating device is located on a surface, facing the fluid, of at least one of the plates.
9. The lithographic apparatus of claim 7 , wherein the heating device is located on a surface, opposite of the fluid, of at least one of the plates.
10. The lithographic apparatus of claim 7 , wherein the at least one optical element comprises a further channel sharing one of the plates of the channel.
11. The lithographic apparatus of claim 10 , wherein the heating device is located on a surface of the shared plate.
12. The lithographic apparatus of claim 1 , wherein the optical elements are comprised in a single structure.
13. The lithographic apparatus of claim 1 , wherein each heating device comprises an elongated conductor.
14. The lithographic apparatus of claim 13 , wherein the elongated conductor comprises one of the group of Cr, Cu, Au and Al.
15. The lithographic apparatus of claim 13 , wherein the cross-section of the elongated conductor conforms to a trapezium-shape.
16. The lithographic apparatus of claim 5 , wherein the fluid comprises a gas.
17. The lithographic apparatus of claim 16 , wherein the gas substantially comprises nitrogen.
18. The lithographic apparatus of claim 5 , wherein the fluid comprises a liquid.
19. A device manufacturing method comprising:
imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;
projecting the patterned radiation beam onto a target portion of a substrate using a projection system;
locally changing an optical path length of the radiation beam using an array of optical elements arranged transverse to the radiation beam, each optical element comprising an individually addressable electrical heating device; and
controlling the heating devices depending on a phase map in a pupil plane of the projection system.
20. The device manufacturing method of claim 19 , further comprising deriving the phase map from an intensity distribution of the radiation beam.
21. The device manufacturing method of claim 19 , further comprising controlling the heating devices depending on a history of previously applied intensity distributions, or a history of applied actuation of the heating devices, or both histories.
22. The device manufacturing method of claim 19 , further comprising transporting a fluid through a channel in at least one optical element of the array of optical elements to establish a static temperature distribution across the at least one optical element.
23. The device manufacturing method of claim 22 , further comprising controlling the heating devices depending on a transport velocity and temperature of the fluid.