Lithography apparatus and a method of manufacturing a device

1. A lithography apparatus comprising:

a projection system configured to project a desired image onto a substrate;

an active module configured to generate a time-varying heat load;

a temperature conditioning system configured to maintain a component of the lithography apparatus at a predetermined target temperature; and

a heat buffer comprising a structure separate from and in contact with the temperature conditioning system, the structure comprising a phase change material in thermal contact with the active module, the phase change material having a phase change temperature such that the phase change material is caused to undergo a phase change by the time-varying heat load,

wherein the temperature conditioning system and heat buffer are configured such that heat is removed from the heat buffer at a lower rate than a peak heat generation rate of the active module.

2. The lithography apparatus according to claim 1 , wherein, during normal operation of the lithography apparatus, the phase change material is stationary relative to the projection system during projection of the desired pattern onto the substrate, during measurement of a property of the substrate, and during positioning of the substrate for the projection and the measurement.

3. The lithography apparatus according to claim 1 , wherein the active module is configured to perform a predetermined operation; and the heat buffer is arranged to capture at least 75% of a total heat output by the active module during the predetermined operation.

4. The lithography apparatus according to claim 3 , wherein the heat buffer comprises sufficient phase change material to absorb by latent heat of phase change at least two times the total heat output by the active module during the predetermined operation.

5. The lithography apparatus according to claim 1 , wherein:

the temperature conditioning system is configured to remove heat from the active module at a predetermined heat removal rate;

the time-varying heat load includes an excess heat generation period in which heat is generated at a rate greater than the predetermined heat removal rate; and

the heat buffer is arranged to capture at least 75% of the heat generated by the active module in excess of the predetermined heat removal rate during the excess heat generation period.

6. The lithography apparatus according to claim 5 , wherein the heat buffer comprises sufficient phase change material to absorb by latent heat of phase change at least two times the heat generated by the active module in excess of the predetermined heat removal rate during the excess heat generation period.

7. The lithography apparatus according to claim 1 , wherein the active module includes an actuator and/or a power electronic device, a substrate stage cleaner or an air gauge.

8. The lithography apparatus according to claim 1 , wherein the active module and the heat buffer are located within a thermally isolated system such that a rate of heat outflow from the thermally isolated system is less than a peak value of the time-varying heat load.

9. The lithography apparatus according to claim 1 , wherein the phase change is a transition from solid to liquid.

10. The lithography apparatus according to claim 1 , wherein the heat buffer further comprises a heat transfer member in thermal contact with the active module and the phase change material.

11. The lithography apparatus according to claim 9 , wherein the heat transfer member has a plurality of fins in contact with the phase change material.

12. The lithography apparatus according to claim 1 , wherein the active module is mounted on the component of the lithography apparatus.

13. The lithography apparatus according to claim 12 , wherein the component of the lithography apparatus is a frame of the lithography apparatus.

14. The lithography apparatus according to claim 1 , further comprising a thermal insulator particularly surrounding the active module and the heat buffer.

15. A device manufacturing method using a lithography apparatus having a projection system and an active module, the method comprising:

operating the active module so that a time-varying heat load is generated;

absorbing the time-varying heat load in a heat buffer comprising a structure separate from and in contact with a temperature conditioning system, the structure comprising a phase change material, by the phase change material undergoing a phase change;

removing heat from the heat buffer at a lower rate than a peak heat generation rate of the active module; and

projecting a desired image onto a substrate using the projection system.

16. The method according to claim 15 , wherein the active module performs a predetermined operation, and the heat buffer captures at least 75% of a total heat output by the active module during the predetermined operation.

17. The method according to claim 15 , wherein;

the temperature conditioning system removes heat from the active module at a predetermined heat removal rate;

the time-varying heat load includes an excess heat generation period in which heat is generated at a rate greater than the predetermined heat removal rate; and

the heat buffer captures at least 75% of the heat generated by the active module in excess of the predetermined heat removal rate during the excess heat generation period.

18. The method according to claim 15 , wherein the active module and the heat buffer are located within a thermally isolated system such that a rate of heat outflow from the thermally isolated system is less than a peak value of the time-varying heat load.

19. The method according to claim 15 , wherein the phase change is a transition from solid to liquid.

20. The method according to claim 15 , wherein the heat buffer further comprises a heat transfer member in thermal contact with the active module and the phase change material.

21. The method according to claim 15 , wherein, during normal operation of the lithography apparatus, the phase change material is stationary relative to the projection system during the projecting the desired image onto the substrate, during measurement of a property of the substrate, and during positioning of the substrate for the projecting and the measurement.