Exposure apparatus and measuring device for a projection lens
View Patent ↗A microlithographic projection exposure apparatus includes a projection lens that is configured for immersion operation. For this purpose an immersion liquid is introduced into an immersion space that is located between a last lens of the projection lens on the image side and a photosensitive layer to be exposed. To reduce fluctuations of refractive index resulting from temperature gradients occurring within the immersion liquid, the projection exposure apparatus includes heat transfer elements that heat or cool partial volumes of the immersion liquid so as to achieve an at least substantially homogenous or at least substantially rotationally symmetric temperature distribution within the immersion liquid.
1. An optical system, comprising:
an illumination system configured to generate projection light;
a projection lens configured to image a mask onto a photosensitive layer, an immersion space being between the projection lens and the photosensitive layer;
an immersion liquid in the immersion space, the immersion liquid being in direct contact with the projection lens and the photosensitive layer to define an interface between the immersion liquid and a surrounding gas, the interface extending between the projection lens and the photosensitive layer;
a heat transfer element configured so that, during an immersion operation, the heat transfer element transfers an amount of heat to or from the immersion liquid: a) at the interface between the immersion liquid and a surrounding gas; or b) within the immersion liquid; and
a control device configured to adjust the amount of heat transferred by the heat transfer element to or from the immersion liquid,
wherein the optical system is a microlithographic projection exposure apparatus.
2. The optical system of claim 1 , wherein the heat transfer element is arranged in the immersion space so that the heat transfer element is in contact with the immersion liquid during an immersion operation.
3. The optical system of claim 2 , wherein the heat transfer element comprises a heating wire.
4. The optical system of claim 1 , wherein the heat transfer element comprises a Peltier element.
5. The optical system of claim 1 , wherein the heat transfer element is arranged at a distance from the immersion space so that heat can be exchanged by thermal radiation between the heat transfer element and the immersion liquid.
6. The optical system of claim 5 , further comprising a directive optical element configured to change a direction of the thermal radiation, the directive optical element being between the heat transfer element and the immersion space.
7. The optical system of claim 6 , wherein the directive optical element has a positive refractive power.
8. The optical system of claim 5 , wherein the heat transfer element comprises a planar radiator configured to be heated or cooled.
9. The optical system of claim 5 , further comprising a thermal sensor configured to measure a temperature of the heat transfer element, wherein the thermal sensor is connected to the control device.
10. The optical system of claim 1 , wherein the heat transfer element is configured to transfer the amount of heat via thermal radiation or thermal conduction.
11. The optical system of claim 1 , wherein the heat transfer element is arranged in a wafer stage configured to position a carrier on which the photosensitive layer is applied.
12. The optical system of claim 11 , wherein the heat transfer element has substantially the same symmetry as a light field that is illuminated on the photosensitive layer during use of the optical system.
13. The optical system of claim 11 , wherein the heat transfer element comprises a plurality of conduits contained in the wafer stage to conduct a heating or cooling medium through the wafer stage.
14. The optical system of claim 1 , wherein the control device is configured to adjust the amount of heat such that the temperature distribution of the immersion liquid is at least substantially homogenous or at least substantially rotationally symmetric.
15. The optical system of claim 1 , wherein, during an immersion operation, the heat transfer element transfers the amount of heat to or from the immersion liquid at the interface between the immersion liquid.
16. The optical system of claim 1 , wherein, during an immersion operation, the heat transfer element transfers the amount of heat to or from the immersion liquid within the immersion liquid.
17. The optical system of claim 1 , wherein:
the heat transfer element is in contact with the immersion liquid; and
during an immersion operation, the heat transfer element transfers heat to or from the immersion liquid within the immersion liquid.
18. The optical system of claim 1 , wherein:
the heat transfer element is arranged outside the immersion liquid; and
the heat transfer element exchanges heat with the immersion liquid via thermal radiation during an immersion operation.
19. An optical system, comprising:
an illumination system configured to generate projection light;
a projection lens configured to image a mask onto a photosensitive layer, an immersion space being between the projection lens and the photosensitive layer;
an immersion liquid in the immersion space, the immersion liquid being in direct contact with the projection lens and the photosensitive layer to define an interface between the immersion liquid and a surrounding gas;
a heat transfer element disposed a distance from the interface so that, during an immersion operation, the heat transfer element exchanges an amount of heat with the immersion liquid via thermal radiation; and
a control device configured to adjust the amount of heat transferred by the heat transfer element to or from the immersion liquid,
wherein the optical system is a microlithographic projection exposure apparatus.
20. The optical system of claim 19 , wherein the heat transfer element is disposed between the projection lens and the photosensitive layer.
21. The optical system of claim 19 , further comprising an optical element configured to change a direction of the thermal radiation, wherein the optical element is between the heat transfer element and the immersion space.
22. The optical system of claim 21 , wherein the optical element has a positive refractive power.
23. The optical system of claim 19 , wherein the heat transfer element comprises a planar radiator configured to be heated or cooled.
24. The optical system of claim 19 , further comprising a thermal sensor configured to measure a temperature of the heat transfer element, wherein the thermal sensor is connected to the control device.