Optical Assembly Thermal Stability via Modified Emission Coefficients
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Solution Overview
Problem
Existing optical assemblies for projection exposure installations, particularly in EUV microlithography, face thermal stability issues due to thermally induced 'bimetal effects' caused by mechanical heat bridges between mirror and support body portions, leading to instability and potential impairment of image-guiding effects.
Innovation Solution
The optical assembly incorporates a thermally modified surface portion on the support body with a differing thermal emission coefficient, creating a thermally separating region between support body portions, which can be further enhanced with microstructures, nanostructures, or surface layers to manage heat emission and reduce temperature differences, and includes active temperature control devices for precise heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a mechanical heat bridge is used to connect mirror body and support body portions, then structural stability is improved, but thermal stability deteriorates due to thermally induced bimetal effects
Solution Approach 1:
The support body is divided into multiple support body portions (first support body portion, second support body portion) that are thermally separated. This segmentation allows each portion to be independently thermally managed, preventing the propagation of thermal gradients that cause bimetal effects while maintaining structural support for the mirror body.
Solution Approach 2:
A thermally separating region is introduced as an intermediary between the first and second support body portions. This region acts as a thermal barrier that blocks heat flow between the portions, eliminating the thermal coupling that causes bimetal effects while still allowing mechanical support functionality.
2Temperature
If thermal emission coefficient is increased to improve heat dissipation, then thermal stability is improved, but energy loss increases
Solution Approach 1:
Different surface portions of the support body are given different thermal emission coefficients through selective surface modification. Areas requiring heat dissipation are modified to have higher emission coefficients, while other areas maintain lower emission coefficients to minimize energy loss. This local differentiation optimizes the balance between thermal stability and energy conservation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances thermal stability by minimizing temperature differences between support body portions, preventing thermally induced instabilities and optimizing heat dissipation, thereby maintaining image quality and extending the operational stability of the optical assembly.
Implementation Method 1
a thermal emission coefficient εm of the modified surface portion differs from a thermal emission coefficient εu of an unmodified surface portion
Data Source
AI summary
An optical assembly has at least one mirror with a mirror body. The latter is carried by a support body, which has a first support body portion and a second support body portion. An at least thermally separating region is arranged between the two support body portions. At least one surface portion of at least one of the support body portions or of a body thermally coupled thereto is modified in such a way that a thermal emission coefficient εm of the modified surface portion differs from a thermal emission coefficient εu of the unmodified surface portion by at least 10%. The result is an optical assembly, in which an improved thermal stability is achieved by the predetermining of the thermal emission coefficients.