Temperature measurement of optical elements in an optical apparatus
AssigneeASML Netherland B.V.
InventorsKoen Martin Willem Jan BOS, Joost André KLUGKIST, Anirudh ANAND
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Abstract
An optical apparatus is disclosed, the apparatus comprising an optical element having a reflective surface for reflecting incident radiation in a beam path, and at least one sensor configured to sense radiation corresponding to a temperature of a respective portion of a backside surface of the optical element. Also disclosed is a method of controlling a temperature of a reflective surface of an optical element in a lithographic apparatus.
Claims19
-19. (canceled)
An optical apparatus comprising:
- an optical element having a reflective surface for reflecting incident radiation in a beam path;
- at least one sensor configured to sense radiation corresponding to a temperature of a respective portion of a backside surface of the optical element;
- and
- at least one coating formed on the respective portion of the backside surface, the at least one coating configured to have temperature-dependent optical properties.
A method of controlling a temperature of a reflective surface of an optical element in a lithographic apparatus, the method comprising:
- configuring at least one sensor to sense radiation corresponding to a temperature of a portion of a backside surface of the optical element;
- and
- using a signal provided by the sensor to configure a temperature controller to control a temperature of the optical element.
Dependencies are inferred from the claim text.