EUV Illumination Stop with Reflective Beam Tube
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Solution Overview
Problem
Current EUV illumination systems face challenges in defining the illumination light beam and managing thermal loading, particularly at constrictions in the beam path, which affects the structure resolution and pupil filling in projection exposure apparatus.
Innovation Solution
A stop is designed with a beam entrance section, a constant cross-section beam tube section, and a beam exit section, where the inner walls of the beam tube section are reflective and the entrance and exit sections can be absorbent, allowing for precise beam shaping and enhanced thermal management by absorbing undesired radiation and debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stop is placed at a constriction of the EUV illumination beam, then the illumination light beam can be well defined, but the thermal loading capacity of the stop is limited
Solution Approach 1:
The patent extends the stop from a simple planar element to a three-dimensional beam tube structure with constant cross-section. This dimensional extension provides a larger surface area for heat dissipation while maintaining the beam-defining function at the constriction point, thus resolving the contradiction between beam definition precision and thermal loading capacity.
Solution Approach 2:
The stop is segmented into distinct functional zones: a beam entrance section, a constant cross-section beam tube section, and a beam exit section. This segmentation allows different parts of the structure to serve different purposes - the beam tube section provides thermal management through its extended surface area, while the entrance and exit sections maintain beam definition, thus resolving the thermal loading limitation.
2Temperature
If the inner wall of the beam tube section is made reflective for EUV illumination light, then the beam course is predetermined and thermal loading capacity is increased, but undesired radiation and debris portions are not effectively removed
Solution Approach 1:
The patent applies different surface properties to different sections of the stop: the beam tube section has reflective inner walls to maintain beam course and dissipate heat, while the beam entrance and exit sections have absorbent inner walls to remove undesired radiation and debris. This local differentiation of surface properties resolves the contradiction between thermal management and harmful factor removal.
Solution Approach 2:
The absorbent sections convert the harmful effect of undesired radiation into beneficial heat dissipation, while the reflective beam tube section converts potential stray light into controlled beam propagation. This transformation of harmful factors into beneficial effects resolves the contradiction between thermal loading capacity and harmful factor removal.
3Device complexity
If a simple stop design is used, then the device complexity is low, but the illumination angle distribution cannot be well controlled
Solution Approach 1:
The patent employs a dynamic geometric design where the beam tube section has a constant cross-section that interacts with the converging beam to naturally define the illumination angle distribution. This geometric dynamic approach achieves precise angular control without complex mechanical adjustments or multiple components, resolving the contradiction between device complexity and illumination precision.
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 configuration enables a well-defined illumination light beam with minimal alteration, improved thermal loading capacity, and enhanced structure resolution, facilitating better imaging and reduced stray light in EUV projection exposure apparatus.
Implementation Method 1
An inner wall of the beam tube section is embodied as reflective for the EUV illumination light
Implementation Method 2
An inner wall of the beam tube section is embodied as absorbent for radiation and/or debris portions that are entrained undesirably with the EUV illumination light. An effective dissipation of heat brought about on account of absorption of undesired light or radiation portions can take place by way of the beam tube section
Data Source
AI summary
A stop is configured to be arranged in a constriction of an EUV illumination light beam between an EUV light source for EUV illumination light and an EUV illumination optical unit. The stop has a beam entrance section, a beam exit section and an intervening beam tube section. The entrance section has a cross section that decreases in the propagation direction of the EUV illumination light beam. The cross section of the exit section increases in the propagation direction. The cross section of the tube section is constant. An inner wall of the beam tube section is embodied as reflective for the EUV illumination light. The result is a stop that can have a defined predetermination of the illumination light beam in conjunction with a good thermal loading capacity of the stop.