Optical Element Damping Device for Lithography Vibration Control
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Solution Overview
Problem
Projection exposure machines for semiconductor lithography face challenges in damping vibrations of optical elements, particularly those with multiple degrees of freedom, leading to reduced natural vibration frequencies and increased risk of excitation by external vibrations.
Innovation Solution
A damping device comprising multiple mass dampers with interconnected damper masses and damping elements, connected via low-mass connecting elements, which are strategically positioned to absorb vibrational energy and eliminate parasitic modes, thereby stabilizing the optical element and reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical elements are made larger and heavier to image smaller structures, then imaging capability is improved, but natural vibration frequencies decrease and susceptibility to external vibrations increases
Solution Approach 1:
The patent converts the harmful effect of low natural vibration frequencies into a beneficial damping effect by introducing mass dampers tuned to resonate at these low frequencies. The damper masses are specifically designed to match the low natural frequencies of large optical elements, transforming the vulnerability to vibrations into an active damping mechanism that absorbs vibrational energy and stabilizes the system.
2Adaptability or versatility
If joints and adjusting elements are used to decouple optical elements, then positioning flexibility is improved, but system stiffness decreases and vibration resistance worsens
Solution Approach 1:
The patent introduces mass dampers as intermediary elements between the optical element and external vibrations. These dampers act as mediators that absorb and dissipate vibrational energy, protecting the optical element from external vibrations while allowing the joints and adjusting elements to maintain their positioning flexibility. The dampers are connected via low-mass connecting elements that minimize interference with the positioning mechanism.
3Reliability
If multiple mass dampers are used to damp multiple degrees of freedom, then vibration damping is improved, but device complexity increases
Solution Approach 1:
The patent segments the damping function into multiple independent mass dampers, each targeting specific degrees of freedom or vibration modes of the optical element. This segmentation allows each damper to be optimized for particular vibration characteristics while maintaining overall system simplicity through modular design. The multiple dampers work independently to address different vibrational aspects without requiring complex interconnected damping mechanisms.
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 damping device effectively absorbs vibrational energy, increases natural frequencies, and reduces aberrations by strategically placing mass dampers and damping elements to match the optical element's vibration forms, ensuring optimal damping and minimizing harmful parasitic frequencies above 1,000 Hz.
Implementation Method 1
vibrational energy of the optical element being dissipated by friction using the additional mass(es)
Implementation Method 2
at least one damping element, and the damper masses of the mass dampers being interconnected
Implementation Method 3
a mass damper with a damper mass and at least one damping element
Data Source
AI summary
A damping device of an optical element of a projection exposure machine includes at least two mass dampers arranged spaced apart from one another, the vibration absorbers each having at least one damper mass and at least one damping element and the damper masses of the at least two mass dampers being interconnected by at least one connecting element. The optical element can be part of a projection exposure machine.