EUV Lithography Optical Assembly Purge Gas Flow Control
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Solution Overview
Problem
Existing optical assemblies used in EUV lithography systems face challenges in effectively purging fastening areas of optical elements, leading to contamination and potential damage from moisture, especially when using small purge gas flows.
Innovation Solution
An optical assembly with a flow guiding element, typically made of metallic materials like stainless steel, is integrated to cover the interstice between the optical element and the mount, allowing a controlled purge gas flow that protects the fastening areas from environmental influences while minimizing the amount of purge gas required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a purge gas flow is used to protect the fastening areas of optical elements, then contamination from moisture is prevented, but the amount of purge gas required increases significantly
Solution Approach 1:
The patent applies local quality by directing the purge gas flow specifically to the fastening areas of the optical element rather than uniformly across the entire optical surface. The gas flow is localized to where contamination risk exists (fastening areas with adhesives), reducing the total purge gas volume while maintaining protection where needed. This is achieved through careful positioning of gas nozzles and shaping the gas flow path to concentrate protection at the mount-optical element interface.
Solution Approach 2:
The patent segments the optical element into distinct regions: the optically active surface and the fastening areas. By separating these functional zones, the purging strategy can be optimized differently for each - the optically active surface receives minimal or no purge gas, while the fastening areas receive targeted protection. This segmentation allows reduction of overall purge gas consumption while maintaining protection where required.
2Strength
If the optical element is laterally clamped by fastening elements, then secure fastening is achieved, but the fastening areas become exposed to ambient moisture and contamination
Solution Approach 1:
The patent applies preliminary anti-action by introducing a purge gas flow that actively counteracts moisture and contamination before they can reach and damage the fastening areas. The gas flow is directed along the lateral surfaces of the fastening elements and at the interface between the mount and optical element, creating a protective barrier that prevents environmental contaminants from contacting the adhesive bonds and fastening surfaces.
Solution Approach 2:
The purge gas acts as an intermediary substance between the ambient environment and the fastening areas. It creates a protective atmosphere that mediates the interaction between moisture/contaminants and the sensitive fastening regions, allowing the fastening structure to remain exposed mechanically while being protected chemically/environmentally by the gas flow barrier.
3Reliability
If a large purge gas volume is used to ensure complete protection, then all surfaces are protected, but system complexity and gas consumption increase
Solution Approach 1:
The patent applies partial action by providing purge gas protection only where it is actually needed - specifically at the fastening areas and mount interfaces - rather than uniformly across all optical surfaces. This selective approach achieves sufficient reliability for protection while avoiding the excessive gas consumption and system complexity that would result from comprehensive uniform protection of all surfaces.
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
This solution significantly reduces the amount of purge gas needed while maintaining effective protection of the fastening areas, achieving a high protection factor against contamination and preventing deformation of the optical elements due to moisture exposure.
Implementation Method 1
a purging device arranged to produce at least one purge gas flow in the region of the optical element, such that the purge gas flow flows around the fastening areas of the fastening elements
Data Source
AI summary
An optical assembly (1) includes an optical element (2), a mount (3) configured to hold the optical element (2), and a plurality of fastening elements (12) with fastening areas (14) configured to fasten the optical element (2) to the mount (3). The fastening elements (12) bridge an interstice (11) between the optical element (2) and the mount (3), and a purge device (15) produces at least one purge gas flow (16) in the region of the optical element (2) such that the purge gas flow flows around the fastening areas (14) of the fastening elements (12).