EUV Reflective Coating Layout for Angle-Dependent Mirror Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reflective optical elements for EUV lithography have low overall reflectivity due to the use of identical reflective coatings across multiple units, which do not account for varying angles of incidence during operation.
Innovation Solution
Divide the reflective optical elements into bandwidth classes and apply multilayer systems with adapted layer sequences and thicknesses to each unit, optimizing the period length based on the specific angle of incidence ranges for each class, allowing for higher reflectivity while maintaining efficient manufacturing and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If identical reflective coatings are applied to all upper units, then manufacturing effort is reduced, but reflectivity decreases due to varying angles of incidence
Solution Approach 1:
The patent applies different reflective coatings to different upper units based on their specific operational parameters. Each upper unit receives a coating optimized for its local angle of incidence range, transforming the uniform coating approach into a localized optimization strategy that maintains high reflectivity while managing manufacturing complexity through systematic classification.
Solution Approach 2:
The patent changes the parameters of the reflective coating (layer sequence, layer thicknesses, period length) to match the specific operational conditions of each upper unit. By adjusting these parameters based on bandwidth classes and angle of incidence ranges, the system achieves optimized reflectivity for each unit while maintaining a structured manufacturing process.
2Reliability
If reflective coatings are optimized for each upper unit, then reflectivity increases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the upper units into bandwidth classes based on their angle of incidence ranges. This segmentation allows for systematic optimization where units within the same class receive identical coatings, reducing the number of unique coating specifications needed while still achieving localized optimization for each unit's operational conditions.
Solution Approach 2:
The patent creates universal coating solutions for groups of upper units with similar operational characteristics. By defining base multilayer systems that can serve multiple upper units within a bandwidth class, the system achieves universality that simplifies manufacturing while maintaining optimized performance for each specific application context.
3Reliability
If base multilayer systems are selected differently for each bandwidth class, then reflectivity optimization is improved, but coating process complexity increases
Solution Approach 1:
The patent applies partial optimization by selecting different base multilayer systems for different bandwidth classes rather than optimizing every single upper unit individually. This partial action approach achieves significant reflectivity improvement for the most critical bandwidth classes while maintaining a manageable coating process complexity through systematic grouping.
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 proposed method significantly increases the reflectivity of reflective optical elements by adapting the reflective coatings to the incidence angles, achieving up to 15% improvement in mean reflectivity and even greater gains at extreme angles, while maintaining manageable manufacturing efforts.
Implementation Method 1
applying a reflective coating to each upper unit, adapted to the angle of incidence and angle of incidence bandwidths determined over its surface
Implementation Method 2
a multilayer system with period length is applied to all upper units as a reflective coating, the layer sequence and/or layer thicknesses of which are adapted to the maximum bandwidth determined for the respective bandwidth class
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The aim of the invention is to increase the reflectivity of a reflective optical element for the extreme ultraviolet wavelength range, consisting of at least two upper units, in which each upper unit (B1-B5) has a plurality of lower units, for example reflective optical elements in the form of mirror arrays. To this end, a method for the production of the reflective optical element is provided, said method comprising the following steps: determination of incidence angles and incidence angle bandwidths occurring during operation above the surface of each upper unit (B1-B5); and application of a reflective coating to each upper unit (B1-B5), adapted to the incidence angles and incidence angle bandwidths respectively determined above the surface of each upper unit. This is particularly suitable for the production of reflective optical elements embodied as field facet mirrors, particularly in the form of microelectromechanical mirror arrays, for an EUV lithography device.