Patent ID: 11892779
Assignee: ASML HOLDING N.V.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 11:
12. A method of thermally conditioning an optical element having a curved optical surface used in a lithographic apparatus, the optical element including a set of closed channels, wherein regions at a heat transfer surface of the optical element that are exposed to the set of closed channels are positioned along a curved profile similar to that of the curved optical surface, the method comprising:
delivering, via a pump, a fluid as a heat transfer medium into the set of closed channels of the optical element;
receiving, via a temperature sensor, temperature values across the curved optical surface, or receiving, via a model, a heat distribution across the curved optical surface; and
controlling, based on the temperature values or the heat distribution, a property of the fluid to maintain a uniform temperature distribution across the optical element during imaging of a pattern using the lithographic apparatus, wherein the controlling comprises:
determining a location on the curved optical surface having relatively high temperature values;
identifying one or more closed channels of the set of closed channels that are nearest to the determined location; and
adjusting the property of the fluid within the one or more closed channels so that temperature at the determined locations is maintained within a desired temperature range.