Liquid Sealing for Lithography Optical Gaps
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Solution Overview
Problem
Conventional sealing methods in projection exposure systems for semiconductor lithography cause unwanted deformation of optical elements due to rigid sealing elements and are inadequate for relative movements, leading to image errors and leaks.
Innovation Solution
An optical assembly with a gap between optical and structural elements, sealed by a liquid layer that allows relative displacement, providing improved sealing and mechanical decoupling, using materials like stainless steel or quartz to prevent ultraviolet radiation interference and maintaining the liquid layer's integrity through surface tension and capillary forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rigid seal is used between optical element and structural element, then sealing is achieved, but forces are exerted on the optical element causing deformation and image errors
Solution Approach 1:
The patent changes the physical state of the sealing element from rigid solid to liquid, fundamentally altering its mechanical properties. The liquid sealing element flows to conform to the optical element's surface, providing sealing without exerting rigid contact forces that cause deformation. This parameter change from solid to liquid state resolves the contradiction between sealing effectiveness and optical element deformation.
Solution Approach 2:
The patent employs a liquid sealing element that utilizes fluid pressure and surface tension to achieve sealing. The liquid layer maintains contact with both the optical element and structural element through capillary forces and surface tension, creating an effective seal without the rigid contact forces that would deform the optical element. This hydraulic approach replaces mechanical contact sealing with fluid-based sealing.
2Reliability
If a conventional rigid seal is used, then sealing is achieved, but relative movements between optical element and structural element are restricted
Solution Approach 1:
The patent changes the sealing element from rigid solid to liquid state, enabling it to adapt to relative movements between the optical element and structural element. The liquid can flow and deform to accommodate positional changes while maintaining sealing contact, whereas a rigid seal would create binding forces that restrict movement. This parameter change provides both sealing effectiveness and movement adaptability.
Solution Approach 2:
The patent introduces dynamic adaptability through the liquid sealing element that can change its configuration in response to relative movements. The liquid layer can flow, shift, and deform dynamically to maintain sealing contact during positional changes, whereas a rigid seal is static and inflexible. This dynamic behavior allows the seal to accommodate thermal expansion, mechanical displacement, and other relative movements.
3Adaptability or versatility
If a leaky seal or gap is used to allow movement, then relative movement is enabled, but sealing is incomplete leading to leaks
Solution Approach 1:
The patent uses a liquid sealing element that exploits fluid pressure and surface tension to achieve complete sealing while allowing relative movement. The liquid layer maintains continuous contact with the optical element and structural element through capillary forces, preventing leaks even when the components move relative to each other. This hydraulic sealing mechanism provides both movement capability and sealing completeness.
Solution Approach 2:
The patent changes the sealing element from rigid to liquid state, enabling it to fill gaps and maintain sealing contact during relative movements. The liquid can flow to compensate for positional changes while maintaining continuous sealing contact, whereas a rigid seal would create gaps or leaks when movement occurs. This parameter change achieves both adaptability and sealing completeness simultaneously.
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 solution effectively seals the gap between optical and structural elements, minimizing image errors and extending the service life by decoupling mechanical stresses and preventing liquid creep into the optically active area, while allowing for precise control of the liquid layer's thickness and geometry.
Implementation Method 1
a liquid layer runs between the sealing element and the structural element or the optical element, along the layer plane of which a relative displacement of the sealing element with respect to the structural element or the optical element is possible
Implementation Method 2
The liquid layer has the effect that on the one hand the area between the sealing element and the structural element or the optical element is sealed
Implementation Method 3
a liquid layer runs between the sealing element and the structural element or the optical element, along the layer plane of which a relative displacement of the sealing element with respect to the structural element or the optical element is possible
Data Source
Figure 1
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AI summary
The assembly has gap between an optical element (8) e.g. plane-parallel plate, and a structure element. A curved liquid layer is in between a sealing element with an undulatory structure made of high grade steel or quartz, and the structure or the optical element. A relative motion is in a direction perpendicular to an optical axis of the assembly between the sealing element and the element. The liquid layer has a layer between the structure and the sealing element, and another layer between the optical and the sealing element.