EUV Mirror Layout for Compact High-Throughput Imaging
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Solution Overview
Problem
Existing EUV projection exposure apparatuses face challenges in achieving a compact structure while maintaining high imaging throughput and efficiency, particularly due to the large size of the last mirror and the need for efficient guidance of the imaging beam path.
Innovation Solution
The proposed imaging EUV optical unit employs a design where the antepenultimate mirror's reflection surface faces the last mirror, allowing the beam path to be guided around it, combined with a configuration of NI and GI mirrors to achieve a compact structure and high throughput, with an overall transmission of greater than 10% and an image-side numerical aperture of less than 0.5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the last mirror is made large to determine the image-side numerical aperture, then the imaging throughput is improved, but the overall device size increases
Solution Approach 1:
The beam path is redirected from a linear sequence to a three-dimensional configuration by introducing the antepenultimate mirror that faces the last mirror. This allows the beam to pass behind the last mirror through the antepenultimate mirror's reflection surface, utilizing spatial reconfiguration to reduce the overall optical unit size while preserving the large last mirror diameter needed for high imaging throughput.
2Device complexity
If the beam path is guided directly through the last mirror, then the optical path is simplified, but the last mirror blocks the beam path and increases the required installation space
Solution Approach 1:
The antepenultimate mirror serves as an intermediary element that redirects the beam path around the last mirror. By positioning the antepenultimate mirror's reflection surface to face the last mirror, the beam is reflected through a path that bypasses the obstruction created by the large last mirror, thereby reducing the required installation space while maintaining optical functionality.
3Area of stationary object
If more mirrors are added to guide the beam path around the last mirror, then the installation space is reduced, but the number of optical elements increases
Solution Approach 1:
The antepenultimate mirror performs multiple functions: it acts as a beam redirecting element to guide the path around the last mirror, serves as a structural component defining the optical cavity, and contributes to the overall optical path length. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving compact installation space.
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 design enables a compact EUV optical unit with improved usability, increased throughput, and reduced wavefront aberration, allowing for efficient imaging with a compact footprint and enhanced exposure power.
Implementation Method 1
a plurality of mirrors for guiding EUV imaging light at a wavelength of shorter than 30 nm along an imaging beam path from the object field towards the image field
Data Source
AI summary
An imaging EUV optical unit serves images an object field into an image field. The imaging optical unit has a plurality of mirrors for guiding EUV imaging light along an imaging beam path. The plurality of the mirrors includes at least two normal incidence mirrors and at least one grazing incidence mirror. The last two mirrors in the imaging beam path are normal incidence mirrors and lack an imaging light passage opening. A reflection surface of an antepenultimate mirror in the imaging beam path faces the last mirror in the imaging beam path. This EUV optical unit can have improved usability for an EUV projection exposure apparatus.