Substrate support structure, clamp preparation unit, and lithography system
View Patent ↗A substrate support structure for clamping a substrate by means of a capillary force created by a liquid clamping layer having a lower pressure than its surroundings. The substrate support structure comprises a surface provided with a plurality of substrate supporting elements for holding the substrate, and the surface further comprises portions with different capillary potential for inducing, during clamping, a predetermined capillary flow within the liquid clamping layer.
1. A substrate support structure for clamping a substrate by means of a capillary force created by a liquid clamping layer having a lower pressure than its surroundings and having an outer liquid surface, the substrate support structure comprising a surface provided with a plurality of substrate supporting elements for holding the substrate, the surface of the substrate support structure comprising a perimeter being circumscribed by a moat, and further comprising surface portions with different capillary potential for inducing, during clamping, a predetermined capillary flow within the liquid clamping layer to replenish evaporating liquid at locations within a portion of the surface of the substrate support structure with a higher capillary potential;
wherein at least a part of the surface portions with a lower capillary potential takes the form of a channel, wherein the channel extends from a predetermined location along the perimeter, and wherein the channel is arranged to induce a capillary flow from the channel to the periphery of the liquid clamping layer.
2. The substrate support structure of claim 1 , wherein the surface portions with different capillary potential further induce, during clamping, sacrificial gap development at one or more predetermined locations along the periphery of the liquid clamping layer.
3. The substrate support structure of claim 1 , wherein the surface of the substrate support structure comprises the surface portions with a lower capillary potential at the perimeter of the substrate support structure surface at one or more predetermined locations while the majority of the perimeter has a higher capillary potential.
4. The substrate support structure of claim 1 , wherein the substrate supporting elements are arranged in a regular pattern with a mutual pitch, and wherein the channel width is smaller than said mutual pitch.
5. The substrate support structure of claim 1 , wherein the channel comprises a curved portion.
6. The substrate support structure of claim 1 , wherein at least a part of the surface portions with a lower capillary potential takes the form of one or more channels.
7. The substrate support structure of claim 6 , wherein the surface area of the one or more channels covers less than 25% of the substrate support structure surface.
8. The substrate support structure of claim 7 , wherein the surface area of the one or more channels is homogeneously spread over the substrate support structure surface.
9. The substrate support structure of claim 8 , wherein the surface portions with a lowest capillary potential is provided at the perimeter of the surface.
10. The substrate support structure of claim 9 , wherein a height difference between the top surface of the substrate supporting elements and a height level of the surface portion with the lowest capillary potential circumscribing the remainder of the surface substantially equals twice the height of the substrate supporting elements provided on the surface portion with a lower capillary potential within the remainder of the surface of the substrate support structure.
11. The substrate support structure of claim 1 , wherein the surface portions with a lowest capillary potential is provided at a circumference of the surface portions with a higher capillary potential.
12. The substrate support structure of claim 1 , wherein the surface portions with different capillary potential have different height levels to provide a difference in capillary potential.
13. The substrate support structure of claim 1 , wherein the surface portions with different capillary potential have different affinity for the clamping liquid to provide a difference in capillary potential.
14. The substrate support structure of claim 13 , wherein the surface portions with different capillary potential have a differing surface treatment, surface material, or surface coating, to provide a difference in capillary potential.
15. The substrate support structure of claim 1 , wherein the substrate support structure further comprises a liquid removal system for removing liquid circumferential to said surface.
16. The substrate support structure of claim 15 , wherein the liquid removal system comprises a gas distribution system.
17. The substrate support structure of claim 16 , wherein the gas distribution system comprises at least one gas inlet for providing gas, and at least one gas outlet for removing gas.
18. The substrate support structure of claim 16 , wherein the substrate support structure further comprises a sealing structure circumscribing the substrate support structure surface such that gas provided by the gas distribution system can flow between the substrate support structure surface and the sealing structure.
19. The substrate support structure of claim 18 , wherein the sealing structure has a height level corresponding with the height level of the plurality of substrate supporting elements.
20. The substrate support structure of claim 18 , wherein the substrate supporting elements are arranged in a regular pattern with a mutual pitch, and the distance between the sealing structure and the nearest substrate supporting elements exceeds said mutual pitch.
21. The substrate support structure of claim 1 , wherein the outer liquid surface is concave-shaped.