Fluid-Channel Damping Arrangement for Optical Element Vibration
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Solution Overview
Problem
In EUV microlithographic projection exposure apparatuses, mechanical vibrations cause instability and deterioration in positional stability and optical performance due to low intrinsic damping of materials used, necessitating additional damping measures.
Innovation Solution
A damping arrangement utilizing a fluid in a cavity with connected channels, where vibrations displace the fluid into the channels, enhancing energy dissipation through friction, allowing effective damping even with low or medium viscosity fluids like water, and potentially eliminating the need for large absorber masses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with high intrinsic damping are used, then vibration damping performance is improved, but material selection is limited and vacuum resistance is compromised
Solution Approach 1:
A fluid intermediary substance is introduced into a cavity within the optical element to provide damping. The fluid acts as a mediator between the vibrating element and the damping mechanism, allowing the element itself to maintain its vacuum-resistant material properties while the fluid provides the necessary damping effect.
Solution Approach 2:
The patent employs a hydraulic damping mechanism by filling a cavity with a fluid that responds to vibrations. The fluid's movement and friction within the cavity create damping forces that reduce vibrations without requiring the structural material itself to have high damping properties, thus preserving material selection flexibility for vacuum resistance.
2Reliability
If absorber masses are used for damping, then vibration damping is achieved, but the system size and complexity increase
Solution Approach 1:
The damping mechanism is nested within the optical element itself by creating a cavity inside the element and filling it with fluid. This nested design integrates the damping function into the existing structure without requiring separate external absorber masses, thereby reducing system size and complexity.
Solution Approach 2:
The optical element serves multiple functions: it maintains its primary optical function while simultaneously housing a damping cavity that contains the fluid damping mechanism. This multi-functionality eliminates the need for separate dedicated damping components, reducing overall system complexity.
3Loss of energy
If high viscosity fluids are used for damping, then energy dissipation is improved, but fluid selection is limited and flow characteristics are compromised
Solution Approach 1:
The damping effect is localized to specific regions within the cavity where fluid friction is maximized, such as near the channel walls or restricted flow paths. This allows the use of lower viscosity fluids that can still provide adequate damping through localized friction zones while maintaining overall fluid flow characteristics and selection flexibility.
Solution Approach 2:
The patent optimizes damping by adjusting geometric parameters of the cavity and fluid pathways rather than relying solely on fluid viscosity. By changing parameters such as cavity shape, channel dimensions, and flow path length, adequate damping is achieved with fluids of lower viscosity, expanding fluid selection options.
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
Achieves efficient damping of high-frequency vibrations with a compact design, reducing the need for large absorber masses and allowing the use of fluids with low to medium viscosity, thereby enhancing the positional stability and optical performance of EUV systems.
Implementation Method 1
The liquid displacement that takes place in the channel can have the consequence that—as a result of the increase in energy dissipation due to the friction occurring on the channel wall—efficient damping can also be achieved
Data Source
AI summary
The disclosure relates to a damping arrangement for vibration damping of an element in an optical system, for example in a microlithographic projection exposure apparatus. A damping arrangement according to the disclosure has an element, a fluid located in a cavity, and at least one channel connected to the cavity. A vibration of the element causes vibration energy of the element to be dissipated by partial displacement of the fluid from the cavity into the at least one channel.