EUV Lithography Mirror with Honeycomb Cavity and Removable Support
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Solution Overview
Problem
EUV lithography apparatuses with large numerical apertures face challenges in producing mirrors with large diameters, as existing solutions result in unfavorable mass distribution, reduced stiffness, increased weight, and larger diameters due to protuberances used for mounting and actuation, which complicates deformation decoupling and dynamic behavior.
Innovation Solution
A method for producing a mirror arrangement with a cavity between the front and rear walls, where a supporting element is initially provided to prevent sagging during production but is then partly removed to decouple the walls mechanically, reducing weight and maintaining stiffness, and using a material with a zero thermal expansion coefficient to minimize temperature effects on imaging properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mirrors with large diameter are produced for EUV lithography apparatuses with large numerical apertures, then the numerical aperture is improved, but the weight increases and stiffness decreases
Solution Approach 1:
The mirror body is designed with a honeycomb-like internal structure consisting of numerous cells with hexagonal cross-sections. This porous configuration significantly reduces the mirror's weight while maintaining structural stiffness and rigidity, enabling large-diameter mirrors to achieve both high numerical aperture and acceptable weight for actuation in EUV lithography apparatuses
2Ease of operation
If protuberances are provided on the mirror substrate for mounting and actuation, then the mirror can be mounted and actuated, but the mass distribution becomes unfavorable and stiffness is reduced
Solution Approach 1:
The harmful protuberances extending far outside the mirror substrate are eliminated. Instead, bearing sections are integrated directly into the mirror body at optimized locations, removing the adverse mass distribution and stiffness reduction caused by external protuberances while maintaining mounting and actuation functionality
Solution Approach 2:
The mirror body is designed with locally optimized bearing sections positioned at specific locations on the mirror substrate, rather than using uniform protuberances. This allows the structure to have different properties at different locations - the bearing sections provide mounting functionality while the majority of the mirror body maintains optimal mass distribution and stiffness
3Weight of moving object
If the mirror body is made thin to reduce weight, then the weight is reduced, but the mirror becomes more sensitive to deformation from small forces
Solution Approach 1:
The honeycomb-like internal structure provides high strength-to-weight ratio, allowing the mirror body to be thin and lightweight while maintaining resistance to deformation. The cellular structure distributes mechanical loads effectively throughout the mirror body, preventing localized deformations even in thin-walled constructions
Solution Approach 2:
The mirror employs a composite structure combining a thin outer shell with an internal honeycomb core, creating a lightweight yet stiff construction. This composite approach allows the mirror to achieve both reduced weight and improved deformation resistance compared to solid thin mirrors
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
The method achieves good deformation decoupling, reduces weight, and maintains stiffness, allowing for improved dynamic properties and reduced temperature dependence, making it suitable for large-diameter mirrors in EUV lithography applications.
Implementation Method 1
a supporting element is initially provided to prevent sagging during production
Implementation Method 2
using a material with a zero thermal expansion coefficient to minimize temperature effects on imaging properties
Data Source
AI summary
A method for producing a mirror arrangement for a lithography apparatus is proposed, which comprises the following steps: producing a mirror body having a cavity delimited by a front wall, a rear wall and a side wall of the mirror body, the side wall being arranged between the front wall and the rear wall, wherein at least one supporting element is provided in the cavity between the front wall and the rear wall; and after producing the mirror body, at least partly removing the supporting element.