US-20260126614-A1 - OPTICAL MODULE AND PROJECTION EXPOSURE SYSTEM

Abstract

An optical module comprises an optical element and a stiffening body. The optical element comprises an optical effective surface. The optical element is connected to the stiffening body by way of a connection element. The connection element comprises a decoupling region which mechanically decouples the stiffening body and the optical element parallel to the optical effective surface.

Inventors

• Jens Kugler
• Andreas Raba
• Marwene Nefzi

Assignees

• CARL ZEISS SMT GMBH

Dates

Publication Date

20260507

Application Date

20251219

Priority Date

20230627

Claims (20)

1. 1 . An optical module, comprising: an optical element comprising an optical effective surface; in a stiffening body; and an actuator connecting the optical element and the stiffening body, wherein: the actuator comprises a region mechanically decoupling the stiffening body and the optical element parallel to the optical effective surface; the region of the actuator is deflectable parallel to the optical effective surface; and a Young's modulus of a material of the stiffening body is at least twice a Young's modulus of a material of the optical element.
2. 2 . The optical module of claim 1 , wherein the stiffening body comprises a ceramic.
3. 3 . The optical module of claim 1 , wherein the actuator is between the optical element and the stiffening body in a direction of an optical axis of the optical module.
4. 4 . The optical module of claim 1 , wherein the actuator comprises at least two regions which are deflectable perpendicular to each other and parallel to the optical effective surface.
5. 5 . The optical module of claim 1 , wherein the region is actively controllable.
6. 6 . The optical module of claim 1 , wherein the actuator comprises a region which is deflectable perpendicular to the optical effective surface.
7. 7 . The optical module of claim 1 , further comprising an evaluation unit connected to the region of the actuator, wherein the evaluation unit is configured to detect mechanical stresses.
8. 8 . The optical module of claim 1 , wherein the stiffening body comprises a thickened region.
9. 9 . The optical module of claim 1 , wherein the stiffening body comprises a stiffening rib.
10. 10 . The optical module of claim 1 , further comprising sensor elements, wherein the stiffening body comprises a thickened region which is a reference region supporting the sensor elements.
11. 11 . The optical module of claim 1 , wherein the optical element and/or the stiffening body comprise fluid channels.
12. 12 . The optical module of claim 1 , wherein the optical element comprises a mirror.
13. 13 . The optical module of claim 1 , wherein the Young's modulus of the material of the stiffening body is at least twice the Young's modulus of the material of the optical element
14. 14 . The optical module of claim 1 , further comprising a passive decoupling element comprising a region which is deflectable parallel to an optical axis of the optical module, wherein the passive decoupling element is coupled to the actuator.
15. 15 . An apparatus, comprising: an optical module according to claim 1 , wherein the apparatus comprises a semiconductor lithography projection exposure apparatus.
16. 16 . The apparatus of claim 15 , further comprising: an illumination optics unit; and a projection optics unit, wherein: the illumination optics unit is configured to illuminate an object field in an object plane of the projection optics unit; the projection optics unit is configured to image the illumination field into an object field in an object plane of the projection optics unit; and the projection optics unit comprises the optical module.
17. 17 . An optical module, comprising: an optical element comprising an optical effective surface; a stiffening body comprising a ceramic; an actuator connecting the optical element and the stiffening body, wherein: the actuator comprises a region mechanically decoupling the stiffening body and the optical element parallel to the optical effective surface; and the region of the actuator is deflectable parallel to the optical effective surface.
18. 18 . The optical module of claim 17 , wherein the stiffening body comprises silicon carbide.
19. 19 . An apparatus, comprising: an optical module according to claim 17 , wherein the apparatus comprises a semiconductor lithography projection exposure apparatus.
20. 20 . The apparatus of claim 19 , further comprising: an illumination optics unit; and a projection optics unit, wherein: the illumination optics unit is configured to illuminate an object field in an object plane of the projection optics unit; the projection optics unit is configured to image the illumination field into an object field in an object plane of the projection optics unit; and the projection optics unit comprises the optical module.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation of, and claims benefit under 35 USC 120 to, international application No. PCT/EP2024/067969, filed Jun. 26, 2024, which claims benefit under 35 USC 119 of German Application Nos. 10 2023 116 895.9 and 10 2023 116 899.1, filed on Jun. 27, 2023. The entire disclosure of each of these applications is incorporated by reference herein. FIELD The disclosure relates to an optical module for a projection exposure apparatus and to a projection exposure apparatus for semiconductor lithography. BACKGROUND Projection exposure apparatuses for semiconductor lithography are used for producing extremely fine structures, for example on semiconductor components or other microstructured components. An idea of the apparatuses involves the production of extremely fine structures down to the nanometer range by way of generally reducing imaging of structures on a mask, a so-called reticle, on an element to be structured, such as, for example, a wafer, that is provided with photosensitive material. The minimum dimensions of the structures produced depend on the resolution of the optical system used for imaging. The resolution, in turn, in general depends directly on the wavelength of the radiation used for imaging, which is known as the used radiation, and the numerical aperture, i.e. the product of the refractive index of the surrounding medium and the opening angle of the optical system used for imaging. Light sources that produce radiation in an emission wavelength range from 100 nm to 300 nm, referred to as the DUV range, are used to produce the used radiation, wherein light sources with an emission wavelength in the order of a few nanometers, for example between 1 nm and 120 nm, for example in the order of 13.5 nm, have found increased use in recent times. The emission wavelength range described last is also referred to as the EUV range. In the optical system, optical elements such as lens elements and mirrors are used to illuminate the structures and for example to image them, wherein mirrors are usually used in the field of EUV lithography on account of the strong absorption of the emission wavelengths used therein by most materials. In order to image the structures, so-called optical effective surfaces of the optical elements are exposed to used radiation. Within the scope of imaging, deviations of the position of the optical elements from an optimum target position typically have a relatively large influence on the quality of image representation and hence on the quality of the components produced. To help meet the stringent desire properties in relation to position, the position of a predominant number of mirrors can be actively controlled. Such closed-loop control typically involves a high control bandwidth, which depends inter alia on the first internal natural frequencies of the optical element or optical module, wherein the lowest internal natural frequency should be above 1500 Hz. Lower natural frequencies can lead to the sensors for the closed-loop control starting to vibrate in the low-frequency range (<1500 Hz), whereby rigid body control for positioning the mirror may become unstable. In addition to the optical element, an optical module additionally comprises at least the actuators and sensors for positioning purposes and the connection thereof to the optical element. The desired natural frequencies, which as shown above are relatively high, involve the use of a certain amount of comparatively expensive materials in order to attain the desired stiffness, especially in view of the main bodies, for example the main bodies of mirrors. In view of this issue, proposals have been made in the past to arrange comparatively thin optical elements on stiffening bodies made of comparatively stiff materials, with these stiff materials not needing to be the relatively expensive known materials of the main bodies of optical elements. However, a challenge remains in view of compensating the deviations between the respective coefficients of thermal expansion of the elements involved, as these are quite significant in this case. SUMMARY The present disclosure seeks to provide an optical module, in which an optical element is arranged on a separate stiffening body and wherein the issue of different coefficients of thermal expansion is effectively counteracted. In an aspect, the disclosure provides an optical module comprising an optical element and a stiffening body, with the optical element comprising an optical effective surface. In this case, the optical element can be connected to the stiffening body by way of at least one connection element. According to the disclosure, the connection element can comprise a decoupling region which provides mechanical decoupling of the stiffening body and the optical element parallel to the optical effective surface. Within the meaning of the disclosure, decoupling means the reduction of the transmission of force