EUV Projection Lens with Concentric Diffraction Patterns
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Solution Overview
Problem
EUV lithography requires an optic system with high transmittance and resolution, but existing EUV projection lenses have low transmittance and high absorptance, making them expensive and prone to aberration and alignment issues.
Innovation Solution
An EUV projection lens with concentric diffraction patterns on a substrate, where the patterns have an out-of-phase height with respect to EUV light, using materials like ruthenium for high transmittance, and optimized line widths and distances to enhance diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mirror coated with multilayers is used to reflect EUV light, then the optic system can function with EUV light source, but the surface quality becomes low and the cost becomes high
Solution Approach 1:
The patent replaces the mechanical mirror reflection system with an optical diffraction system. Instead of using a mirror coated with multilayers to reflect EUV light, the invention uses a diffraction lens with concentric patterns that diffract EUV light to achieve focusing. This substitution eliminates the need for complex mirror coatings and their associated surface quality issues while maintaining EUV light compatibility.
Solution Approach 2:
The patent changes the optical parameter approach from reflection-based to diffraction-based. By using a diffraction lens with specific pattern parameters (concentric circles with controlled line widths and spacing), the system achieves EUV light manipulation without requiring the complex surface parameters needed for multilayer mirror coatings.
2Adaptability or versatility
If a mirror coated with multilayers is used to reflect EUV light, then the optic system can function with EUV light source, but the alignment optimization becomes difficult
Solution Approach 1:
The patent replaces the mechanical mirror alignment system with a diffraction-based optical system. The diffraction lens inherently provides alignment tolerance through its pattern geometry, eliminating the need for precise alignment optimization required by mirror systems. The concentric diffraction patterns create robust optical paths that are less sensitive to alignment variations.
3Ease of manufacture
If conventional materials are used for the projection lens, then the lens structure can be formed, but the transmittance becomes low and absorptance becomes high
Solution Approach 1:
The patent applies local quality by creating regions of different optical properties within the lens. The diffraction patterns are formed with specific line widths and spacing that create alternating regions of material and substrate, optimizing local light interaction. This local structuring enables high transmittance in the substrate regions while maintaining structural integrity through the patterned regions.
Solution Approach 2:
The patent changes the material parameter approach by using a substrate material with high EUV transmittance and forming diffraction patterns with optimized geometric parameters. Instead of relying on conventional lens materials with poor EUV transmission, the invention uses a diffractive optical element where the pattern geometry (line width, spacing, depth) controls the optical function while the substrate material provides high transmittance.
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 EUV projection lens achieves high transmittance and resolution, reducing light source power and increasing signal-to-noise ratio, while being cost-effective and minimizing noise from zero and second-order diffraction lights.
Implementation Method 1
concentric diffraction patterns on the substrate. The concentric diffraction patterns may have an out-of phase height with respect to EUV light
Data Source
AI summary
An EUV projection lens includes a substrate and concentric diffraction patterns on the substrate. The concentric diffraction patterns have an out-of phase height with respect to EUV light and include a material through which the EUV light has a transmittance higher than about 50% at the out-of phase height. The EUV projection lens has a high first order diffraction light efficiency and an optic system having the EUV projection lens has a high resolution.