EUV Mirror Capping Layer with Particle Coating for Contamination Resistance
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Solution Overview
Problem
EUV mirrors in microlithographic projection exposure apparatuses are susceptible to molecular contamination, which impairs their reflection properties and reduces the apparatus's performance due to the lack of effective contamination resistance in existing capping layers.
Innovation Solution
Applying particles of a second material, differing from the capping layer material, onto the surface of the EUV mirror to block surface defects and prevent contamination deposition, thereby reducing reactivity and enhancing contamination resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capping layer is applied onto the reflection layer system to suppress diffusion of oxygen and protect from EUV radiation damage, then the reflection layer system is protected from chemical degradation, but the capping layer itself becomes susceptible to molecular contamination (e.g., by hydrocarbons) which impairs reflection properties
Solution Approach 1:
The patent applies a composite structure consisting of the original capping layer (first material) combined with particles of a second material having different properties. This composite structure leverages the protective qualities of the capping layer while the particles of second material provide contamination resistance, creating a multi-functional surface layer that addresses both protection and contamination prevention requirements
Solution Approach 2:
The patent modifies only the outer surface of the capping layer by applying particles of second material, rather than changing the entire capping layer structure. This localized modification preserves the bulk protective properties of the capping layer while adding contamination resistance only where needed at the surface level
2Ease of manufacture
If the capping layer is made from a single material to simplify manufacturing, then the production process is easier and more consistent, but the single material cannot simultaneously provide both EUV radiation protection and contamination resistance
Solution Approach 1:
The patent creates a composite system where particles of second material are applied onto the capping layer of first material. This composite approach enables the capping layer to fulfill multiple functions: the first material provides EUV radiation protection and structural integrity, while the second material particles provide contamination resistance, achieving versatility without requiring complete redesign of the manufacturing process
Solution Approach 2:
The particles of second material are applied in advance onto the capping layer before the mirror enters service, creating a pre-established contamination-resistant surface. This preliminary action ensures that the multi-functional properties are in place before operation begins, allowing the single-material capping layer to be manufactured first and then enhanced with the particle coating
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 application of these particles effectively reduces contamination on the mirror's surface, maintaining the reflection properties and performance of the projection exposure apparatus during operation and transport.
Implementation Method 1
a reflection layer system for reflecting electromagnetic radiation that is incident on the optically effective surface
Implementation Method 2
particles of a second material are applied onto this capping layer... block surface defects and prevent contamination deposition
Data Source
AI summary
A mirror, in particular for a microlithographic projection exposure apparatus, has a mirror substrate (101), a reflection layer system (102) configured to reflect electromagnetic radiation that is incident on the optically effective surface (100a), and a capping layer (104), which is arranged on the side of the reflection layer system (102) facing the optically effective surface. The capping layer is produced from a first material. Particles (105) of a second material, either individually or in clusters, are applied onto this capping layer, wherein the second material differs from the first material.