Heat pipe, lithographic apparatus and device manufacturing method
A lithographic apparatus is provided that includes a substrate holder configured to hold a substrate, and a heat pipe to maintain the substrate holder at a substantially uniform temperature. The heat pipe has a chamber containing a liquid reservoir and a vapor space, and a heating element at least partly in contact with liquid in the chamber.
1. A substrate table system, comprising:
a substrate holder configured to hold a substrate; and
a heat pipe configured to maintain the substrate holder at a substantially uniform temperature, the heat pipe comprising:
a chamber containing a liquid reservoir and a vapor space; and
a heating element at least partly in contact, in use, with liquid in the chamber, the heating element, in use, being substantially at or overlapping an interface between the liquid and the vapor in the chamber.
2. The substrate table system of claim 1 , further comprising a liquid transporter configured to apply a force to liquid to transport liquid away from a condensing surface at least partly defining the chamber towards the reservoir.
3. The substrate table system of claim 2 , wherein the heating element is positioned in the liquid transporter.
4. The substrate table system of claim 2 , wherein the liquid transporter is a passive liquid transporter.
5. The substrate table system of claim 2 , wherein the liquid transporter is configured to apply the force to the liquid by capillary action.
6. The substrate table system of claim 2 , wherein the liquid transporter comprises a porous material.
7. The substrate table system of claim 2 , wherein the liquid transporter is in the form of a plurality of projections extending towards the condensing surface from the reservoir.
8. The substrate table system of claim 1 , further comprising a structural member extending between a condensing surface and a bottom wall of the chamber opposite the condensing surface.
9. The substrate table system of claim 1 , wherein the heating element is positioned at least partly within the reservoir.
10. The substrate table system of claim 9 , wherein the heating element is elongate in a first direction and is positioned such that the first direction is substantially perpendicular to a top surface of liquid in the reservoir.
11. The substrate table system of claim 1 , further comprising a porous member substantially covering a bottom wall of the chamber.
12. The substrate table system of claim 11 , wherein the heating element is at least partly in the porous member.
13. The substrate table system of claim 1 , wherein the heat pipe further comprises a pressure sensor configured to measure vapor pressure in the vapor space.
14. The substrate table system of claim 1 , wherein the heat pipe further comprises a temperature sensor.
15. The substrate table system of claim 14 , further comprising a controller configured to control the heating element.
16. The substrate table system of claim 15 , wherein the controller is configured to control the heating element to maintain the temperature and/or pressure within the chamber substantially constant.
17. The substrate table system of claim 1 , wherein the heating element is positioned outside of the reservoir.
18. An apparatus, comprising:
a substrate holder configured to hold a substrate;
a heat pipe configured to maintain the substrate holder at a substantially uniform temperature, the heat pipe comprising:
a chamber containing a liquid reservoir and a vapor space, and
a heating element at least partly in contact, in use, with liquid in the chamber, the heating element, in use, being substantially at or overlapping an interface between the liquid and the vapor in the chamber;
a projection system configured to project a beam of radiation onto the substrate; and
a liquid supply system configured to provide a liquid between the projection system and the substrate holder.
19. A method, comprising:
holding a substrate on a substrate holder; and
maintaining the substrate holder at a substantially uniform temperature using a heat pipe, the heat pipe comprising a chamber containing a liquid and a vapor and a heating element at least partly in contact with the liquid in the chamber, the heating element being substantially at or overlapping an interface between the liquid and the vapor in the chamber.
20. The method of claim 19 further comprising providing liquid between a projection system and the substrate holder and projecting a beam of radiation, using the projection system, onto the substrate.