Optical system, and method for operating an optical system

Patent metadata

Field	Value
Publication number	US-12571983-B2
Application number	US-202318328154-A
Country	US
Kind code	B2
Filing date	Jun 2, 2023
Priority date	Jan 28, 2021
Publication date	Mar 10, 2026
Grant date	Mar 10, 2026

Abstract

An optical system, for example in a microlithographic projection exposure apparatus, comprises a mirror and a temperature-regulating device. The mirror has an optical effective surface and a mirror substrate. A plurality of temperature-regulating zones are arranged in the mirror substrate. The temperature-regulating device is used to adjust the temperatures present in each of the temperature-regulating zones independently of one another. The temperature-regulating zones are arranged in at least two planes at different distances from the optical effective surface. The temperature-regulating zones in the at least two planes are configured as cooling channels through which, independently of one another, a cooling fluid at a variably adjustable cooling fluid temperature is able to flow. A method for operating such an optical system is provided.

First claim

What is claimed is:

1 . An optical system, comprising:
a mirror comprising an optically effective surface and a mirror substrate, the mirror substrate comprising a plurality of temperature control zones; a temperature control device configured to set temperatures in the temperature control zones independently of one another; and a device, wherein:
the temperature control zones are in two planes at different distances from the optically effective surface;
the temperature control zones in the two planes comprise cooling channels through which, independently of one another, a cooling fluid with a variably settable cooling fluid temperature is flowable; and
the device is configured to ascertain a cooling power that is output when the cooling fluid flows through the cooling channels.

2 . The optical system of claim 1 , further comprising a regulation unit configured to temporally variably regulate the temperatures set in the temperature control zones by the temperature control device.

3 . The optical system of claim 2 , wherein the regulation unit is configured so that a determination, underlying the regulation, of a current heating state of the mirror is performed based on the cooling power that is output by the cooling fluid when it flows through the cooling channels.

4 . The optical system of claim 1 , wherein:
the mirror substrate comprises a first mirror substrate part comprising a first mirror substrate material; the mirror substrate comprises a second mirror substrate part on a side of the first mirror substrate part facing away from the optically effective surface; and the second mirror substrate part comprises a second mirror substrate material different from the first mirror substrate material.

5 . The optical system of claim 4 , wherein the two planes are assigned to different mirror substrate parts.

6 . The optical system of claim 4 , wherein the first mirror substrate material has a lower average coefficient of thermal expansion than the second mirror substrate material.

7 . The optical system of claim 1 , wherein:
a first plurality of temperature control zones are in a first plane of the two planes; and the temperature control zones located in the first plane are settable independently of one another.

8 . The optical system of claim 1 , wherein the temperature control device comprises a plurality of Peltier elements, and each Peltier element is assigned to a respective temperature control zone.

9 . The optical system of claim 1 , wherein the temperature control device comprises a plurality of radiant heaters, and each radiant heater is assigned to a respective temperature control zone.

10 . The optical system of claim 1 , wherein the optically effective surface is configured to reflect electromagnetic radiation at a wavelength of less than 30 nm.

11 . The optical system of claim 1 , wherein the optical system is a projection lens a microlithographic projection exposure apparatus, or the optical system is an illumination device of a microlithographic projection exposure apparatus.

12 . A method, comprising:
providing the optical system of claim 1 ; and setting the temperatures in the temperature control zones independently of one another so that a deformation, due to different thermal expansion of the temperature control zones belonging to different of the two planes, corresponds to a desired deformation.

13 . The method of claim 12 , further comprising temporally variably regulating the temperatures respectively set in the temperature control zones.

14 . The method of claim 12 , further comprising flowing the cooling fluid through the cooling channels while independently variably setting the temperature of the cooling-fluid temperature in the cooling channels.

15 . The method of claim 12 , further comprising:
flowing the cooling fluid through the cooling channels; ascertaining a cooling power that is output when the cooling fluid flows through the cooling channels; and performing a determination, underlying the regulation, of a current heating state of the mirror based on the ascertained cooling power.

16 . An optical system, comprising:
a mirror comprising an optically effective surface and a mirror substrate, the mirror substrate comprising a plurality of cooling channels therein, the cooling channels configured so that, independently of one another, a cooling fluid with a variable cooling-fluid temperature is flowable therethrough; a device configured to ascertain a cooling power output when the cooling fluid flows through the cooling channels; and a regulating unit configured to temporally variably regulate temperatures set in the temperature control zones via the temperature control device, wherein a determination, underlying this regulation, of a current heating state of the mirror is performable based on the ascertained cooling power output when the cooling fluid flows through the cooling channels.

17 . A method, comprising:
providing the optical system of claim 16 ; and setting the temperatures in the temperature control zones independently of one another so that a deformation, due to different thermal expansion of the temperature control zones belonging to different of the two planes, corresponds to a desired deformation.

18 . A method of operating an optical system, the optical system comprising a mirror, the mirror comprising an optically effective surface and a mirror substrate, the mirror substrate comprising cooling channels therein and through which, independently of one another, a cooling fluid with a variably settable cooling-fluid temperature is flowable, the method comprising:
ascertaining a cooling power that is output when the cooling fluid flows through the cooling channels;
performing a determination of a current heating state of the mirror based on the ascertained cooling power; and
using the determined current heating state to regulate the a temperature set in the temperature control zones in a temporally variable manner.

19 . The optical system of claim 2 , wherein the regulation unit is configured so that a determination, underlying this regulation, of a current heating state of the mirror is performable based on the ascertained cooling power output when the cooling fluid flows through the cooling channels.

20 . The optical system of claim 16 , wherein:
the mirror substrate comprises a first mirror substrate part comprising a first mirror substrate material; the mirror substrate comprises a second mirror substrate part on a side of the first mirror substrate part facing away from the optically effective surface; and the second mirror substrate part comprises a second mirror substrate material different from the first mirror substrate material.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Dirauf Andre
• Gruner Toralf
• Baer Norman
• Monz Thomas
• Buettner Paul

Classifications

• G03F7/70316

  Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements · CPC title

• G03F7/70233

  Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems · CPC title

• G03F7/702

  Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems · CPC title

• G02B7/1815 Primary

  with cooling or heating systems (cooling arrangements for laser mirrors H01S3/0401) · CPC title

• G03F7/70266 Primary

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