EUV Intensity Adaptation Filter with Spatially Varying Thickness
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Solution Overview
Problem
EUV microlithography projection exposure apparatuses face challenges in adapting to different light sources and intensity distributions, requiring a solution to ensure homogeneous illumination and compensate for variations in light intensity across the reticle plane.
Innovation Solution
An intensity adaptation filter with an absorber layer is used, which can be applied to a substrate or be self-supporting, varying in thickness to compensate for different intensity distributions, and can be designed as a transmission or reflective filter, utilizing materials like molybdenum, ruthenium, or silicon to achieve wavelength-independent intensity adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different light sources are used in EUV illumination systems, then versatility and adaptability are improved, but intensity distribution uniformity deteriorates
Solution Approach 1:
The filter features a spatially varying thickness profile, where different regions of the filter have different thicknesses to compensate for local intensity variations in the illumination. This local quality variation allows the filter to adapt to different light source intensity distributions while maintaining uniform illumination across the reticle plane.
Solution Approach 2:
The filter's optical properties are modified by changing its thickness parameter across different spatial locations. This parameter change (thickness variation) enables the filter to adapt to different light sources by adjusting the optical path length and absorption characteristics in different regions, thereby compensating for intensity non-uniformities.
2Illumination intensity
If filter thickness is varied to compensate intensity distributions, then illumination uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The filter combines multiple functions into a single component: it serves as both an intensity adaptation element and an illumination uniformity correction element. By merging the thickness variation function with the filtration function, the patent reduces the need for multiple separate components while achieving intensity compensation.
Solution Approach 2:
The filter implements local quality variation through controlled thickness changes in specific regions. This allows precise compensation of intensity non-uniformities without requiring complex multi-component systems, as the local thickness variations are directly deposited or formed during the filter manufacturing process.
3Adaptability or versatility
If absorber layer thickness is increased to adapt emission characteristics, then intensity adaptation capability is improved, but light transmission is reduced
Solution Approach 1:
The absorber layer thickness is optimized locally rather than uniformly across the entire filter. In regions where higher adaptation is needed, the thickness is increased to provide greater absorption and emission characteristic adaptation. In regions where transmission is critical, the thickness is reduced to maintain light efficiency, achieving a balanced local optimization.
Solution Approach 2:
The absorber layer thickness parameter is dynamically optimized based on the specific light source being used and the desired emission characteristic adaptation. By adjusting this parameter locally rather than uniformly, the system achieves effective emission adaptation while minimizing overall light transmission losses.
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 filter effectively adapts the emission characteristic of light sources, ensuring consistent intensity distribution in the reticle plane, allowing for the use of various light sources and reducing production complexity by integrating intensity adaptation into existing components like mirrors.
Implementation Method 1
an absorber layer for the used working light, in particular EUV radiation
Data Source
AI summary
An optical element for an optical system that operates with working light in the wavelength spectrum of extreme ultraviolet light or soft X-ray radiation, in particular an optical system for EUV microlithography, that includes an absorber layer (12) for EUV or soft X-ray radiation. The absorber layer extends along an optically effective surface and has a thickness that is defined transversely with respect to the optically effective surface, wherein the thickness of the absorber layer varies over the optically effective surface. Also disclosed is a mirror formed by at least one roughened surface of the mirror, the roughness of which varies over the surface. In addition, an illumination system for an EUV projection exposure apparatus, and a method for producing a corresponding intensity adaptation filter are disclosed.