Method for heating an optical element in a microlithographic projection exposure apparatus and optical system

Patent metadata

Field	Value
Publication number	US-12353141-B2
Application number	US-202318342377-A
Country	US
Kind code	B2
Filing date	Jun 27, 2023
Priority date	Feb 10, 2021
Publication date	Jul 8, 2025
Grant date	Jul 8, 2025

Abstract

A method of heating an optical element in a microlithographic projection exposure apparatus and an optical system includes using a heating arrangement to introduce a heating power into the optical element. The heating power is regulated based on a setpoint value. The setpoint value is varied over time during the operation of the projection exposure apparatus. Varying the setpoint value for the heating power comprises a simulation of the effects of changes in the heating power relative to the actual value thereof based on a model for the thermal behavior of the optical element.

First claim

What is claimed is:

1. A method, comprising:
using a heating arrangement to introduce a heating power into an optical element in a microlithographic projection exposure apparatus, the optical element comprising a temperature sensor, the heating power being controlled based on a setpoint value for a temperature attained at a location of the temperature sensor;
measuring wavefront data of the microlithographic projection exposure apparatus;
modelling wavefront properties of the microlithographic projection exposure apparatus;
comparing the measured wavefront data to the modelled wavefront properties; and
based on the comparison of the measured wavefront data and the modelled wavefront properties, varying a setpoint value for the temperature attained at the location of the temperature sensor during operation of the projection exposure apparatus, thereby varying the heating power.

2. The method of claim 1 , comprising varying the setpoint value taking into account an illumination setting currently set in the projection exposure apparatus.

3. The method of claim 1 , comprising varying the setpoint value taking into account a reticle currently used in the projection exposure apparatus.

4. The method of claim 1 , comprising varying the setpoint value based on a measurement of an intensity distribution currently present in a predetermined plane of the projection exposure apparatus.

5. The method of claim 1 , comprising generating the model taking into account a known spatial distribution of a zero crossing temperature in a material of the optical element.

6. The method of claim 1 , comprising generating the model using an artificial intelligence method, wherein the model is trained using a multiplicity of training data in a learning phase, and each training datum comprises values of the heating power and wavefront properties of projection exposure apparatus assigned to the values.

7. The method of claim 6 , wherein the training data are at least partially based on a model-based simulation of the wavefront properties to be expected for different operating conditions of the projection exposure apparatus.

8. The method of claim 6 , wherein the training data are at least partially based on wavefront properties measured in the projection exposure apparatus for different operating conditions.

9. The method of claim 1 , comprising heating the optical element to reduce a spatial and/or temporal variation of a temperature distribution in the optical element.

10. The method of claim 1 , comprising heating the optical element to at least partially compensate an optical aberration caused elsewhere in the projection exposure apparatus.

11. The method of claim 1 , wherein the optical element comprises a mirror.

12. The method of claim 1 , comprising operating the microlithographic projection exposure apparatus using an operating wavelength of less than 30 nm.

13. The method of claim 1 , wherein varying the setpoint value for the temperature attained at the location of the temperature sensor comprises a simulation of respective effect of changes in the heating power on a wavefront provided by the projection exposure apparatus in an image or wafer plane of a projection lens of the microlithographic projection exposure apparatus.

14. The method of claim 1 , comprising, for a model-aided determination of effects of a change in the heating power, implementing an optical forward propagation for the projection exposure apparatus.

15. The method of claim 14 , comprising using a measurement of a wavefront provided in a plane of the projection exposure apparatus to calibrate the forward propagation or the model.

16. A method of manipulating a temperature of an optical element in a microlithographic projection exposure apparatus, the optical element comprising a temperature sensor, the method comprising:
varying a setpoint value of a temperature attained at a location of the temperature sensor during operation of the projection exposure apparatus based on a comparison of a simulation of a respective effect of changes in the heating power with its actual value with regard to the wavefront properties provided by the projection exposure apparatus based on a model of thermal behavior of the optical element; and
using the setpoint value to control heating power that is introduced into the optical element.

17. The method of claim 16 , wherein varying the setpoint value of the temperature attained at the location of the temperature sensor comprises a simulation of respective effect of changes in the heating power on a wavefront provided by the projection exposure apparatus in an image or wafer plane of a projection lens of the microlithographic projection exposure apparatus.

18. The method of claim 16 , comprising, for a model-aided determination of effects of a change in the heating power, implementing an optical forward propagation for the projection exposure apparatus.

19. The method of claim 18 , comprising using a measurement of a wavefront provided in a plane of the projection exposure apparatus to calibrate the forward propagation or the model.

20. An optical system, comprising:
an optical element comprising a temperature sensor;
a heating arrangement configured to heat the optical element; and
a control unit configured to provide closed-loop control of the heating power introduced into the optical element by the heating arrangement based on a setpoint value for a temperature at a location of the temperature sensor,
wherein:
the setpoint value is variable over time during operation of the optical system;
the variation of the setpoint value comprises a simulation of a respective effect of changes in the heating power in comparison with its actual value with regard to the wavefront properties provided by the optical system based on a model for the thermal behavior of the optical element; and
the optical system is an optical system of a microlithographic projection exposure apparatus.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Hellweg Dirk

Classifications

• G03F7/70266

  Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction · CPC title

• G02B5/0891

  Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06) · CPC title

• G03F7/70525

  Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure · CPC title

• G03F7/70891 Primary

  Temperature · CPC title

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title