Eddy Current Damper for Lithography Optical Element Vibration
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Solution Overview
Problem
Conventional lithographic systems face challenges with high-frequency vibrations causing pattern placement errors due to insufficient damping in optical element mounts, leading to increased costs and reduced throughput, as well as instability from excessive damping or over-constraint.
Innovation Solution
The implementation of an eddy current damper system with conducting plates and alternating magnetic layers to provide controlled damping, stabilizing optical elements and improving motion stability without over-constraining the system, using a motion amplifier for enhanced damping effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical element mounts are used with minimal damping, then the system maintains freedom of motion and avoids over-constraint, but high-frequency vibrations cause pattern placement errors
Solution Approach 1:
The patent replaces conventional mechanical damping mounts with an eddy current damper system that uses electromagnetic induction. The eddy current damper comprises a magnet assembly and a conductive plate, where relative motion between the magnet and conductor generates eddy currents that produce a damping force opposing the vibration. This electromagnetic-based damping mechanism provides vibration suppression without the mechanical contact and over-constraint issues of traditional mechanical mounts.
Solution Approach 2:
The eddy current damper acts as an intermediary between the optical element and the vibration source. The magnet assembly is coupled to the optical element while the conductive plate is attached to the housing, creating a damping interface that selectively attenuates high-frequency vibrations without rigidly coupling the optical element to the housing. This intermediary damping mechanism allows the optical element to maintain its required freedom of motion while suppressing harmful vibrations.
2Object-affected harmful factors
If excessive damping is applied to optical element mounts, then vibrations are suppressed, but the system becomes unstable due to over-constraint
Solution Approach 1:
The patent replaces mechanical damping mounts with an eddy current damper system that uses electromagnetic induction. The eddy current damper comprises a magnet assembly and a conductive plate, where relative motion between the magnet and conductor generates eddy currents that produce a damping force opposing the vibration. This electromagnetic-based damping mechanism provides vibration suppression without the mechanical contact and over-constraint issues of traditional mechanical mounts.
Solution Approach 2:
The eddy current damping force is proportional to the velocity of relative motion between the magnet and conductor, providing a velocity-dependent damping effect that naturally adapts to different vibration amplitudes. This parameter-based damping mechanism ensures that damping force is applied only when motion occurs, avoiding the static over-constraint and instability associated with mechanical pre-loaded damping mounts.
3Reliability
If conventional damping mounts are used, then some vibration suppression is achieved, but overlay performance deteriorates and image smearing increases
Solution Approach 1:
The patent replaces conventional mechanical damping mounts with an eddy current damper system that uses electromagnetic induction. The eddy current damper comprises a magnet assembly and a conductive plate, where relative motion between the magnet and conductor generates eddy currents that produce a damping force opposing the vibration. This electromagnetic-based damping mechanism provides vibration suppression without the mechanical contact and over-constraint issues of traditional mechanical mounts.
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 improves overlay performance in maskless lithography systems, reduces image smearing in conventional scanners, and enhances stability in traditional stepper systems, effectively tolerating acoustic and base vibrations while maintaining lens alignment.
Implementation Method 1
The rod causes the conducting plates to move relative to the alternating layers of magnets to generate eddy currents within each of the conducting plates, such that the eddy currents damp the motion of an optical element
Implementation Method 2
alternating layers of magnets. The alternating layers have alternating magnetic fields. When an optical element moves, the optical element will exert a force on the rod. The rod causes the conducting plates to move relative to the alternating layers of magnets to generate eddy currents
Data Source
AI summary
The present invention is directed to optical element damping systems. In particular, an eddy current damper is disclosed. The eddy current damper includes a rod, a series of conducting plates coupled to the rod, and layers of magnets. The alternating layers have alternating magnetic fields. When an optical element moves, the optical element will exert a force on the rod. The rod causes the conducting plates to move relative to the alternating layers of magnets to generate eddy currents within each of the conducting plates, such that the eddy currents damp the motion of an optical element. In an alternative embodiment, an eddy current damper motion amplifier is used to provide additional mechanical advantage that significantly increases the damping provided by the eddy current damper. Eddy current dampers are provided within conventional scanning lithography devices and optical maskless lithography devices to improve performance by stabilizing optical element motion.