EUV Imaging Optics With Large Image Field and High Transmission
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Solution Overview
Problem
Existing EUV projection exposure apparatuses face challenges in achieving high transmission and large maximum image field extent simultaneously, limiting throughput and exposure capabilities.
Innovation Solution
The development of an imaging EUV optical unit with a plurality of mirrors that achieves an overall transmission greater than 5% and a maximum image field extent of over 50 mm, utilizing anamorphic designs and specific mirror configurations to optimize illumination and imaging, including combinations of normal and grazing incidence mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of mirrors and their individual transmission are increased to achieve high overall transmission (>5%), then the exposure power and throughput are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent optimizes the angle of incidence parameters for each mirror to maximize EUV transmission. By carefully selecting and adjusting the incidence angles (using grazing incidence for most mirrors and normal incidence for others), the system achieves >5% overall transmission while managing complexity through parameter optimization rather than simply adding more components.
Solution Approach 2:
The optical system uses composite mirror designs with different incidence types (grazing and normal) combined in specific configurations. This composite approach allows the system to achieve high transmission by leveraging the strengths of different mirror types while maintaining a manageable number of components.
2Productivity
If the image field extent is increased to >50 mm to enable simultaneous exposure of multiple fields, then the productivity is improved, but the manufacturing precision and imaging quality control become more difficult
Solution Approach 1:
The patent divides the large image field (>50 mm) into multiple exposure fields that can be simultaneously exposed. By segmenting the field and using a tailored image field shape (such as annular or segmented rectangular patterns), the system achieves high productivity while maintaining imaging quality through localized optimization of each segment.
Solution Approach 2:
The optical system is designed with local quality optimization, where different regions of the optical path are optimized for specific functions. The mirror configurations and coatings are tailored to maintain uniform imaging quality across the entire large field extent, with particular attention to edge and corner regions that are typically more difficult to control.
3Device complexity
If the overall mirror surface area is reduced to <1.5 m² to simplify the apparatus, then the device complexity is reduced, but the exposure power and transmission capability are limited
Solution Approach 1:
The patent employs anamorphic (non-circular) mirror surfaces and optimized geometric configurations that maximize the effective reflecting area within a compact footprint. By utilizing three-dimensional spatial arrangement and non-uniform surface distributions, the system achieves high exposure power with reduced overall mirror surface area (<1.5 m²).
Solution Approach 2:
The system optimizes the numerical aperture and f-number parameters to maximize the utilization of available mirror surface area. By carefully controlling these optical parameters and the angular distribution of rays, the system achieves high exposure power efficiency, extracting maximum performance from limited mirror surface resources.
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 enhances throughput by allowing simultaneous exposure of adjacent fields, reducing the need for higher power sources, and improving exposure power and efficiency in EUV projection exposure apparatuses.
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 for imaging an object field into an image field. A plurality of mirrors serve 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. An overall transmission of the plurality of mirrors for the EUV imaging light is greater than 5%. The image field of the imaging optical unit has a maximum extent of more than 26 mm in an image plane. This can yield an imaging EUV optical unit with improved usability for an EUV projection exposure apparatus.