Three-Dimensional Aperture Diaphragm for EUV Optical Systems
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Solution Overview
Problem
Conventional aperture diaphragms in EUV exposure apparatuses suffer from optical performance deterioration due to suboptimal positioning and shape, leading to image distortion and reduced accuracy in pattern formation on wafers, as they do not adapt to the actual pupil shape of the optical system.
Innovation Solution
A three-dimensional aperture diaphragm design that warps its inner circumferential surface to match the actual pupil shape, ensuring that the contour of the aperture is curved and aligned with the main light beam, thereby improving optical performance by aligning with the optimal pupil heights in various orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional circular aperture diaphragm is used in EUV exposure apparatus, then the device structure is simple and easy to manufacture, but the optical performance deteriorates due to mismatch with the actual pupil shape
Solution Approach 1:
The aperture diaphragm transitions from a conventional two-dimensional circular shape to a three-dimensional shape that conforms to the actual pupil geometry. The inner circumferential surface is warped to match the pupil's three-dimensional structure, enabling accurate light flux definition while maintaining ease of manufacture through standardized fabrication processes.
Solution Approach 2:
The aperture diaphragm employs non-uniform local geometry where the inner circumferential surface is selectively warped in specific regions to match the actual pupil shape. This localized adaptation allows the aperture to define light flux accurately in different orientations while maintaining a relatively simple overall structure.
2Reliability
If the aperture diaphragm is positioned to define light flux, then the optical path is controlled, but image distortion occurs due to suboptimal positioning relative to the actual pupil
Solution Approach 1:
The aperture diaphragm is pre-shaped with a warped inner circumferential surface that anticipates and compensates for the actual pupil geometry. This preliminary geometric adaptation ensures that when the aperture defines the light flux, it already accounts for the three-dimensional pupil structure, preventing image distortion before it occurs.
Solution Approach 2:
The aperture diaphragm's geometric parameters are changed from a uniform circular cross-section to a variable cross-section that reflects the actual pupil's three-dimensional shape. This parameter transformation enables the aperture to maintain optimal positioning for light flux definition while adapting to variations in pupil geometry across different orientations.
3Manufacturing precision
If a three-dimensional aperture shape is implemented, then optical performance is enhanced by matching the actual pupil shape, but the device complexity increases
Solution Approach 1:
The aperture diaphragm incorporates a three-dimensional shape by warping the inner circumferential surface to match the actual pupil geometry. This dimensional enhancement improves optical performance by accurately defining the light flux in accordance with the pupil's three-dimensional structure, while the overall device complexity remains manageable through efficient design.
Solution Approach 2:
The three-dimensional complexity is localized to the inner circumferential surface of the aperture diaphragm, while the outer structure and mounting mechanisms remain relatively simple. This localized complexity approach enhances optical performance where needed without significantly increasing overall device complexity.
Data Source
AI summary
An aperture diaphragm plate is provided to define a light flux on a pupil plane of an optical system or a plane or surface disposed in the vicinity of the pupil plane. An aperture, which is formed in the aperture diaphragm plate, has a three-dimensional shape corresponding to an optimum pupil shape of the optical system. It is possible to improve the imaging characteristic brought about by the optical system by providing the optimum pupil shape of the optical system.