Laser Beam Guiding Device with Flexure Bearings for Thermal Stability
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Solution Overview
Problem
In drive lasers for EUV lithography, rigid connections between the body and bracket of optical beam guiding devices lead to stress and displacements due to differing thermal expansion coefficients, causing laser beam drift and power output fluctuations.
Innovation Solution
A beam guiding device with a body connected to a bracket via a first and second flexure bearing and a revolute joint, allowing translational and rotational movements to compensate for thermal expansion, minimizing tilting and stabilizing the optical beam guiding element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid connection is used between the body and bracket, then structural strength and position stability are improved, but thermal expansion stress causes body tilting and beam drift
Solution Approach 1:
The connection type is changed from rigid to flexible through the introduction of flexure bearings, allowing the system to adapt to thermal expansion while maintaining structural integrity. The flexure bearings provide controlled degrees of freedom that accommodate dimensional changes without compromising the overall connection strength.
Solution Approach 2:
Flexure bearings are introduced as intermediary elements between the body and bracket, serving as mediators that decouple the rigid connection while maintaining structural support. These intermediaries absorb thermal expansion stresses and prevent direct stress transmission that would cause body tilting.
2Adaptability or versatility
If different materials with different thermal expansion coefficients are used for body and bracket, then design flexibility is improved, but thermal expansion mismatch causes stress and displacements
Solution Approach 1:
The system accommodates different material parameters (thermal expansion coefficients) by introducing flexible connection elements that can adapt to the dimensional changes of each material independently, allowing optimal material selection for each component without being constrained by thermal expansion matching.
Solution Approach 2:
The connection system transitions from a static rigid structure to a dynamic flexible connection that can adapt its configuration in response to thermal expansion differences. The flexure bearings enable the structure to dynamically adjust to dimensional changes caused by different material thermal properties.
3Device complexity
If the body is directly connected to the bracket, then device complexity is reduced, but beam drift and power output fluctuation increase
Solution Approach 1:
Flexure bearings are introduced as intermediary components between the body and bracket, serving as simple yet effective elements that improve beam alignment reliability without significantly increasing overall device complexity. These intermediaries provide the necessary flexibility to maintain reliable beam alignment under thermal conditions.
4Force
If a rigid connection is used, then inertial forces are effectively absorbed, but thermal influence causes body tilting
Solution Approach 1:
The rigid connection is segmented into multiple functional elements: the revolute joint for rotational movement and flexure bearings for translational accommodation. This segmentation allows different parts of the connection system to handle different types of forces and deformations independently.
Solution Approach 2:
The connection system becomes dynamic with the revolute joint allowing controlled rotation to absorb inertial forces while flexure bearings provide flexible support that prevents thermal tilting. The system can dynamically respond to different force types without compromising orientation stability.
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 suppresses laser beam drift and enhances stability by absorbing inertial forces and thermally induced deformations, maintaining beam alignment and power consistency.
Implementation Method 1
If the body is directly connected to the bracket a rigid connection can be achieved. However, such rigid connection can be detrimental when the body and/or the bracket heat up during operation of the system. As the body and the bracket typically are made from materials with different coefficients of thermal expansion
Implementation Method 2
The revolute joint, which can also be referred to as pin joint or hinge joint, constrains the motion of the body relative to the bracket to pure rotation along an axis. This joint provides a rigid connection that is able to absorb inertial forces of the system
Data Source
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AI summary
The present invention concerns a beam guiding device (200) for guiding laser radiation, comprising a body (201) with an inner beam channel (202), an optical beam guiding element (205), in particular a mirror, that is arranged inside the beam channel and a bracket (203) for holding the body (201), wherein the body (201) is connected to the bracket (203) via a first flexure bearing (207), a second flexure bearing (208) and a revolute joint (209). The invention further concerns a lithography system (101), in particular extreme ultraviolet lithography system, comprising a drive laser (100) with a beam guiding device (200) as mentioned before.