Connecting Element Mass Distribution for EUV Optical Stability
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Solution Overview
Problem
In microlithographic projection exposure apparatuses, especially those using EUV, parasitic vibrations are introduced due to frequency-dependent parasitic stiffness in the connecting elements, which can transfer unwanted forces and deflections to optical elements, compromising decoupling and leading to vibrations being transferred to the optical element or mirror.
Innovation Solution
The connecting elements are designed with a non-uniform mass distribution along their length, optimizing the moment of inertia and mass to minimize frequency-dependent parasitic stiffness, achieved by adjusting the moment of inertia to be between 50% and 150% of the value calculated by (L−Ls)Lsmpin, allowing for reduced parasitic stiffness contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If connecting elements are designed with uniform mass distribution, then manufacturing is simple, but parasitic vibrations are transferred to optical elements
Solution Approach 1:
The connecting element is designed with non-uniform mass distribution, creating different local properties along its length. The mass is concentrated at specific locations rather than being uniformly distributed, which modifies the moment of inertia to minimize frequency-dependent parasitic stiffness and reduce vibration transfer to optical elements.
2Reliability
If connecting elements are made flexible to reduce stiffness, then decoupling from parasitic forces is improved, but structural strength decreases
Solution Approach 1:
The connecting element's moment of inertia is optimized by adjusting mass distribution parameters. This parameter change allows the element to maintain appropriate flexibility for decoupling from parasitic forces while preserving sufficient structural strength through the strategic placement of mass along the element's length.
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 design effectively minimizes parasitic vibration excitations during actuation and bearing of optical elements, ensuring reduced vibrations and maintaining the functionality of the connecting elements, thereby enhancing the stability of the optical system.
Implementation Method 1
the mass mpin of the connecting element is distributed over its length L in such a way that the moment of inertia I of the connecting element is increased
Data Source
AI summary
An assembly, for example in a microlithographic projection exposure apparatus, comprises an optical element and a joint arrangement for mechanically bearing the optical element. The joint arrangement comprises at least one connecting element secured on the optical element. The mass of the connecting element is distributed over its length so that the moment of inertia of the connecting element is increased in comparison with a connecting element of identical mass and length in which the mass is distributed uniformly over the length.