Y-Zernike Polynomial Mirror Surfaces for EUV Projection Optics
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Solution Overview
Problem
Current optical structures for microlithography imaging systems face challenges in imaging small features with extreme ultraviolet wavelengths at high numerical aperture and large field of view while maintaining small residual aberrations and being manufacturable with existing techniques.
Innovation Solution
The design of optical components using a Y-Zernike polynomial to describe optical surfaces, allowing for the creation of optical structures with six mirrors, each with a Y-Zernike polynomial surface, which enables imaging at extreme ultraviolet wavelengths with high numerical aperture and large field of view, and minimizes residual aberrations, while being manufacturable with current techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional rotationally symmetric aspheric surface prescriptions are used, then manufacturing is simpler, but residual wavefront aberrations increase (greater than 20 milliwaves at NA 0.35)
Solution Approach 1:
The patent changes the mathematical parameters used to describe optical surfaces from conventional rotationally symmetric aspheric prescriptions to Y-Zernike polynomials. This parameter transformation enables precise control of wavefront aberrations while maintaining manufacturability, achieving residual aberrations of less than 20 milliwaves at NA 0.35.
Solution Approach 2:
The patent introduces asymmetric field points out of the plane of symmetry into the optical design. By optimizing the optical surfaces to handle these asymmetric field conditions, the system achieves superior aberration correction without requiring fully asymmetric surface geometries that would be difficult to manufacture.
2Measurement precision
If high numerical aperture and large field of view are achieved, then imaging resolution improves, but residual aberrations increase
Solution Approach 1:
The patent employs Y-Zernike polynomial parameters to describe optical surfaces, enabling the system to achieve high numerical aperture (NA 0.35) and large field of view (26x2 mm) while maintaining residual wavefront aberrations below 20 milliwaves. This parameter approach allows simultaneous optimization of resolution and aberration control.
Solution Approach 2:
The optical design process incorporates iterative optimization where field points out of the plane of symmetry are used to feedback and adjust the Y-Zernike polynomial coefficients. This ensures that the optical surfaces are precisely tuned to correct aberrations across the entire field of view at high NA.
3Ease of manufacture
If optical structures with small asymmetry are designed, then manufacturability with current techniques is maintained, but imaging performance at high NA and large field of view becomes difficult to achieve
Solution Approach 1:
The patent uses Y-Zernike polynomial parameterization to describe optical surfaces that have small asymmetries. This allows the surfaces to be manufactured with current techniques while still achieving the required imaging performance at high NA and large field of view, as the polynomial coefficients can be precisely controlled to optimize both manufacturability and 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 approach allows for higher resolution and light throughput with reduced manufacturing complexity, achieving residual wavefront aberrations of less than 20 milliwaves at NA 0.35, which is not possible with conventional rotationally symmetric aspheric surface prescriptions, and maintains the ability to manufacture components with existing techniques.
Implementation Method 1
an optical mirror component for a projection optics system comprises an optical surface
Data Source
AI summary
Optical structure and design concepts are provided, using a Y-Zernike polynomial, and by which optical components, optical components and optical structures, can be designed and produced, to image at extreme ultraviolet (EUV) wavelengths, at a relatively high NA (e.g. 0.35), with a relatively large field of view (e.g. 26×2 mm). Moreover, an optical structure produced according to the principles of the present invention has a small amount of asymmetry, which enables the components of the optical structure to be manufactured with current manufacturing techniques.