Magnetic Weight Compensation Assembly for Microlithography Optics
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Solution Overview
Problem
In microlithographic projection exposure apparatuses, mechanical attachments for weight compensating devices lead to dynamic vibration modes and parasitic forces during movement of optical elements, impairing stability and optical performance, while purely magnetic attachments without mechanical guidance result in deformations due to varying magnetic ring distances.
Innovation Solution
A weight compensating assembly using a magnetic circuit with a coil arrangement that can be energized with electrical current to actively compensate for parasitic forces, eliminating mechanical attachments and guidance, and utilizing the stray magnetic field for force compensation, allowing independent optimization of the design and reducing deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a mechanical attachment (pin) is used to connect the weight compensating device to the optical element, then the mechanical guidance provides stable positioning, but dynamic vibration modes and parasitic forces are introduced that impair stability and increase sensitivity to disturbances
Solution Approach 1:
The patent replaces the mechanical pin attachment with a magnetic field-based coupling system. The weight compensating device uses magnetic fields to exert forces on the optical element without physical contact, thereby eliminating mechanical vibration modes and parasitic forces while maintaining positioning stability through controlled magnetic interaction.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the weight compensating device and the optical element. This magnetic field mediator transmits forces without direct mechanical contact, avoiding the transmission of harmful vibrations and parasitic forces while maintaining the necessary force transmission for weight compensation.
2Object-affected harmful factors
If purely magnetic attachment without mechanical guidance is used, then dynamic vibration modes are eliminated, but varying distances between magnetic rings during movement cause parasitic forces that deform the optical element
Solution Approach 1:
The patent employs dynamic control of the magnetic field to compensate for varying distances between magnetic rings during optical element movement. By actively adjusting the magnetic field strength and distribution in response to position changes, the system maintains constant force application without causing deformations, thereby eliminating harmful vibration modes while preserving optical element shape.
Solution Approach 2:
The patent implements a feedback control system that monitors the position of the optical element and adjusts the magnetic field parameters accordingly. This feedback mechanism compensates for distance variations between magnetic rings, ensuring that parasitic forces are minimized and the optical element maintains its intended shape during six-degree-of-freedom movement.
3Shape
If the force transmission is positioned close to the neutral plane of the mirror to avoid parasitic moments, then deformations are minimized, but installation space requirements increase
Solution Approach 1:
The patent applies magnetic field force transmission at multiple localized positions around the optical element rather than requiring a single large-area arrangement. By distributing the magnetic actuators and target elements in space, the system achieves force transmission near the neutral plane while maintaining a compact overall configuration that minimizes installation space requirements.
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 solution enhances the stability of optical elements by reducing parasitic forces and deformations, improving the dynamic behavior and sensitivity to disturbances, while allowing for a compact and efficient design that minimizes installation space and heat conduction issues.
Implementation Method 1
A magnetic field generated by the magnetic circuit brings about a force for compensating at least partially for the force of the weight acting on the optical element
Implementation Method 2
at least two Lorentz actuators
Implementation Method 3
The coil arrangement is energizable with electrical current to generate a compensating force acting on the optical element
Data Source
AI summary
The disclosure relates to an assembly in a microlithographic projection exposure apparatus, with an optical element and at least one weight compensating device, which includes at least one magnetic circuit. A magnetic field generated by this magnetic circuit brings about a force for compensating at least partially for the force of the weight acting on the optical element. The apparatus also includes a coil arrangement with a plurality of coils. The arrangement is energizable with electrical current to generate a compensating force acting on the optical element. This compensating force compensates at least partially for a parasitic force that is exerted by the magnetic circuit when there is movement of the optical element and does not contribute to the compensation for the force of the weight acting on the optical element.