EUV Optical Shield for Plasma Etching Protection
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Solution Overview
Problem
EUV lithography optical arrangements face performance degradation due to etching effects from surrounding hydrogen plasma, leading to reduced transmission and productivity as etching products deposit on reflective optical elements.
Innovation Solution
An optical arrangement with a shield fitted to surface regions of the main body, positioned close to the protected area, utilizing materials with high hydrogen recombination coefficients and stress-compensating layers to prevent etching and maintain reflectivity, with the shield either as a screen or coating applied directly to the main body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the optical arrangement operates in a vacuum environment with hydrogen plasma, then EUV radiation transmission is improved, but etching products deposit on reflective optical elements causing performance degradation
Solution Approach 1:
A shield made of material with high hydrogen recombination coefficient (such as tungsten, tantalum, or iridium) is introduced as an intermediary component between the hydrogen plasma and the reflective optical elements. This shield absorbs hydrogen atoms through recombination, preventing them from reaching and depositing on the optical surfaces, thus protecting the system while maintaining vacuum operation for EUV transmission
2Object-affected harmful factors
If a shield is added to protect against plasma etching, then protection against etching products is improved, but device complexity increases
Solution Approach 1:
The shield serves multiple functions simultaneously: it acts as a protective barrier against hydrogen plasma etching, functions as a hydrogen recombination surface to reduce atomic hydrogen flux, and can be integrated with existing optical component mounts or housings. This multi-functionality reduces the need for additional separate protection systems, thereby limiting the increase in device complexity
3Object-affected harmful factors
If the shield is positioned close to the optical element surface, then etching protection is improved, but the shield may interfere with optical imaging properties
Solution Approach 1:
The shield is designed with spatially varying properties: it is positioned close to the optical element surface in regions where hydrogen plasma exposure is highest (such as peripheral or non-optical areas), while maintaining sufficient distance or being absent in regions where optical imaging occurs. This local differentiation provides maximum protection where needed while minimizing interference with optical performance
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
Effectively protects the optical elements from hydrogen plasma etching, maintaining reflectivity and productivity by preventing material removal and deposition of etching products, while ensuring minimal impact on the optical arrangement's imaging properties.
Implementation Method 1
a distance between the shield and the protected surface region of the main body is less than double the Debye length, preferably less than the Debye length, particularly preferably less than one third of the Debye length, of the surrounding plasma
Implementation Method 2
said coating containing a material having a hydrogen recombination coefficient of 0.08 or higher in order to reduce the inflow rate of activated hydrogen
Data Source
AI summary
An optical arrangement (1) for EUV radiation includes: at least one reflective optical element (16) having a main body (30) with a coating (31) that reflects EUV radiation (33). At least one shield (36) is fitted to at least one surface region (35) of the main body (30) and protects the at least one surface region (35) against an etching effect of a plasma (H+, H*) that surrounds the reflective optical element (16) during operation of the optical arrangement (1). A distance (A) between the shield (36) and the surface region (35) of the main body (30) is less than double the Debye length (λD), preferably less than the Debye length (λD), of the surrounding plasma (H+, H*).