Lithographic apparatus and device manufacturing method
View Patent ↗In an immersion lithography apparatus or device manufacturing method, the position of focus of the projected image is changed during imaging to increase focus latitude. In an embodiment, the focus may be varied using the liquid supply system of the immersion lithographic apparatus.
1. A lithographic apparatus, comprising:
an illumination system configured to condition a beam of radiation;
a support structure configured to hold a patterning device, the patterning device configured to impart the beam with a pattern in its cross-section;
a substrate table configured to hold a substrate;
a projection system configured to project the patterned beam onto a target portion of the substrate;
a liquid supply system configured to fill a space between the projection system and the substrate with a liquid; and
a beam controller configured to focus the patterned beam at a plurality of positions, along a direction substantially parallel to an optical axis of the projection system, relative to the substrate during projection of the patterned beam.
2. The apparatus according to claim 1 , wherein the patterned beam is focused at the plurality of positions by action of the immersion liquid.
3. The apparatus according to claim 1 , wherein the beam controller is configured to vary the position of focus by moving a final element of the projection system.
4. The apparatus according to claim 3 , wherein the final element is movable by action of pressure of the liquid.
5. The apparatus according to claim 4 , wherein movement of the substrate is effective to generate the pressure.
6. The apparatus according to claim 3 , wherein the final element is tilted relative to other optical elements in the projection system.
7. The apparatus according to claim 3 , wherein the final element is moved in a direction substantially parallel to an optical axis of the apparatus.
8. The apparatus according to claim 1 , wherein the beam controller is configured to control the liquid supply system to vary the position by altering the refractive index of the liquid.
9. The apparatus according to claim 8 , wherein the refractive index is altered by a change in composition of the liquid.
10. The apparatus according to claim 8 , wherein the refractive index is altered by a change in temperature of the liquid.
11. The apparatus according to claim 1 , wherein the beam controller is configured to vary the position of focus by moving the substrate, by broadening a bandwidth of the beam of radiation, by providing a further beam of radiation of a different wavelength to the patterned beam, by tilting the patterned beam with respect to the substrate, by moving the patterning device, or by any combination of the foregoing.
12. A device manufacturing method, comprising:
providing a liquid to a space between a projection system of a lithographic apparatus and a substrate;
projecting a patterned beam of radiation, using the projection system, through the liquid onto a target portion of the substrate; and
focusing the patterned beam of radiation at a plurality of positions, along a direction substantially parallel to an optical axis of the projection system, relative to the substrate during projection of the patterned beam.
13. The method according to claim 12 , comprising focusing the patterned beam of radiation at the plurality of positions by action of the liquid.
14. The method according to claim 12 , comprising focusing the patterned beam of radiation at the plurality of positions by movement of a final element of the projection system.
15. The method according to claim 14 , comprising moving the final element by action of pressure of the liquid on the final element.
16. The method according to claim 15 , comprising generating the pressure in the liquid by movement of the substrate.
17. The method according to claim 14 , comprising tilting the final element relative to other optical elements in the projection system.
18. The method according to claim 14 , comprising moving the final element in a direction substantially parallel to an optical axis of the lithographic apparatus.
19. The method according to claim 12 , comprising focusing the patterned beam of radiation at the plurality of positions by altering the refractive index of the liquid.
20. The method according to claim 19 , wherein altering the refractive index of the liquid comprises changing the composition of the liquid.
21. The method according to claim 20 , wherein altering the refractive index of the liquid comprises changing the temperature of the liquid.
22. The method according to claim 12 , comprising focusing the patterned beam of radiation at the plurality of positions by moving the substrate, by broadening a bandwidth of the patterned beam of radiation, by providing a further beam of radiation of a different wavelength to the patterned beam of radiation, by tilting the patterned beam of radiation with respect to the substrate, by moving the patterning device, or by any combination of the foregoing.