EUV Imaging Optics Mirror Spacing Configuration
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Solution Overview
Problem
Current imaging optics systems face challenges in achieving a manageable combination of small imaging errors, efficient production, and high throughput, particularly when dealing with small wavelengths of light, such as EUV wavelengths, due to limitations in mirror design and surface geometry.
Innovation Solution
The design incorporates a plurality of mirrors with a specific configuration where the first mirror has a larger mirror spacing and smaller angles of incidence, utilizing a static free form surface that deviates minimally from an aspherical surface, allowing for high reflection efficiency and reduced intensity loading, while maintaining manufacturing accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the first mirror is positioned closer to the image plane with larger mirror spacing, then the angles of incidence are reduced and manufacturing precision is improved, but the reflection surface area must be carefully controlled to maintain numerical aperture
Solution Approach 1:
The patent applies parameter changes by optimizing the mirror spacing parameter to achieve a balance between imaging precision and surface area. By setting the first mirror spacing to be greater than the last mirror spacing, the system achieves reduced imaging errors while controlling the reflection surface area to maintain numerical aperture performance.
2Reliability
If small angles of incidence are used on the first mirror, then EUV wavelength reflection efficiency is improved, but the mirror must be designed with specific spacing constraints
Solution Approach 1:
The patent uses parameter changes to optimize the mirror spacing configuration for EUV wavelength reflection. By establishing specific spacing relationships where the first mirror spacing is greater than the last mirror spacing, the system achieves high reflection efficiency at small angles of incidence while managing the overall device complexity.
3Productivity
If the first mirror has low intensity loading, then production efficiency is improved, but the reflection surface area is constrained
Solution Approach 1:
The patent applies parameter changes to optimize the intensity loading distribution on the first mirror. By controlling the mirror spacing parameter, the system achieves low intensity loading that improves production efficiency while constraining the reflection surface area to maintain optical performance.
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 results in improved imaging performance with reduced imaging errors, high structure resolution, and efficient production of microstructured or nanostructured components across various wavelengths, including EUV ranges.
Implementation Method 1
an imaging optics with a plurality of mirrors which image an object field in an object plane into an image field in an image plane
Data Source
AI summary
Imaging optics includes a first mirror in the imaging beam path after the object field, a last mirror in the imaging beam path before the image field, and a fourth to last mirror in the imaging beam path before the image field. In an unfolded imaging beam path between the object plane and the image plane, an impingement point of the chief ray on a used region of each of the plurality of mirrors has a mirror spacing from the image plane. The mirror spacing of the first mirror is greater than the mirror spacing of the last mirror. The mirror spacing of the fourth to last mirror is greater than the mirror spacing of the first mirror. Chief rays that emanate from points of the object field that are spaced apart from another have a mutually diverging beam course, giving a negative back focus of the entrance pupil.