EUV Collector Mirrors with Polynomial Corrective Shapes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV and X-ray collector optical systems face challenges in increasing collector efficiency and achieving uniform far field intensity distribution, which affects lithographic processes due to mirror thickness-induced shadowing and thermal limitations.
Innovation Solution
A nested Wolter I collector optical system with polynomial corrective shapes on its mirrors redirects radiation to fill dips in the far field intensity distribution, optimizing the mirror geometry and thermal management to enhance collection efficiency and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the mirror thickness is increased to provide sufficient mechanical stiffness and thermal conductance, then the mechanical strength and thermal management improve, but the shadowing effect increases causing non-uniform far field intensity distribution
Solution Approach 1:
The patent applies different surface profiles to different regions of the mirror. The incident surface has a first profile (e.g., concave) and the emergent surface has a second profile (e.g., convex), creating locally differentiated optical properties that compensate for shadowing effects while maintaining structural integrity
Solution Approach 2:
The patent modifies the geometric parameters of the mirror surfaces by introducing specific profile equations (e.g., polynomial expressions for surface height as a function of radial position) that adjust the optical path to compensate for shadowing caused by finite mirror thickness
2Object-generated harmful factors
If the mirror thickness is reduced to minimize shadowing, then the far field intensity distribution uniformity improves, but the mechanical stiffness and thermal conductance decrease
Solution Approach 1:
By applying asymmetric surface profiles where the incident surface differs from the emergent surface, the design achieves optimal optical performance with reduced thickness, as each surface is locally optimized for its specific functional requirement
Solution Approach 2:
The mirror employs composite construction with reflective coatings on substrates of optimized thickness, combining materials with different properties to achieve both mechanical strength and minimal shadowing effect
3Object-generated harmful factors
If the mirror thickness is reduced to improve shadowing, then the far field intensity distribution uniformity improves, but the thermal conductance decreases affecting thermal management
Solution Approach 1:
The patent utilizes thin mirror shells with optimized surface profiles that minimize shadowing while incorporating thermal management features, allowing efficient heat dissipation despite reduced thickness
Solution Approach 2:
The mirror employs composite construction with reflective coatings on substrates of optimized thickness, combining materials with different properties to achieve both mechanical strength and minimal shadowing effect
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 solution significantly improves the far field intensity distribution uniformity and collector efficiency by redirecting radiation, reducing the impact of mirror thickness shadowing and thermal constraints, thereby enhancing the quality of lithographic processes.
Implementation Method 1
Each mirror has at least a incident surface and an emergent surface with a common axis of symmetry. The incident surface has a first surface profile and the emergent surface has a second surface profile, both extending along a common axis of symmetry. The first and second surface profiles are configured to reflect and redirect radiation respectively.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A collector optical system for extreme ultraviolet (EUV) or X-ray applications, including lithography and imaging, comprising: a plurality of mirrors arranged in nested configuration, the or each mirror being symmetric about an optical axis extending through the radiation source and the or each mirror having at least first and second reflective surfaces, whereby, in use, radiation from the source undergoes successive grazing incidence reflections at said first and second reflective surfaces; and characterised in that one or more of said at least first and second reflective surfaces incorporates a corrective shape so as to compensate the high spatial frequency variation of the far field intensity distribution of said radiation. Also disclosed is a collector optical system for EUV and X-ray applications, in which radiation is collected from a radiation source and directed to an image focus, comprising: a plurality of mirrors arranged in a nested configuration, the or each mirror being symmetric about an optical axis extending through the radiation source and the or each mirror having first and second reflective surfaces, whereby, in use, radiation from the source undergoes successive reflections at said first and second reflective surfaces; and characterised by one or more of the mirrors further comprising a third reflective surface, whereby, in use, radiation from the source undergoes successive reflections at said first, second and third reflective surfaces. Also disclosed is a collector optical system for EUV and X-ray applications, in which radiation is collected from a radiation source and directed to an image focus, comprising: a plurality of mirrors arranged in a nested configuration, the or each mirror being symmetric about an optical axis extending through the radiation source and the or each mirror having first and second reflective surfaces, whereby, in use, radiation from the source undergoes successive grazing incidence reflections at said first and second reflective surfaces; and characterised by at least two of the mirrors having different geometries, and by the plurality of mirrors being optically matched.