Lorentz Actuator Homogeneous Field Halbach Magnet Design
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Solution Overview
Problem
Lithographic apparatuses face overlay errors and imaging problems due to motor position-dependent variations in the motor constant of Lorentz actuators, caused by inhomogeneous magnetic fields and structural inaccuracies.
Innovation Solution
The design incorporates a Halbach configuration with a first and second magnet assembly, each comprising a main and outer subsidiary magnet system, arranged to create a homogeneous magnetic field between the main magnet pairs, with the distance between outer subsidiary magnet systems in a perpendicular direction minimized to reduce motor constant variations and enhance positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a Lorentz actuator uses a conventional magnet configuration, then the device complexity is reduced, but the motor constant varies with position causing overlay errors
Solution Approach 1:
The magnet system is divided into multiple magnet assemblies, each containing main magnets and subsidiary magnets. This segmentation allows the magnetic field to be shaped and controlled more precisely, reducing motor constant variations while maintaining manageable device complexity through modular construction
Solution Approach 2:
Different regions of the magnet system have different magnet orientations and configurations. The subsidiary magnets are specifically oriented to correct local field inhomogeneities, creating a more uniform magnetic field in the critical working region between main magnet pairs
2Stability of the object's composition
If the distance between outer subsidiary magnet systems is increased, then the magnetic field homogeneity is improved, but the device size and complexity increase
Solution Approach 1:
The subsidiary magnets are positioned asymmetrically relative to the main magnets, with specific orientation patterns that create field-correcting effects. This asymmetric configuration achieves field homogeneity without requiring symmetric expansion of the overall actuator size
Solution Approach 2:
The magnetic field homogeneity is achieved by utilizing the perpendicular dimension through specific orientation of subsidiary magnets. Rather than increasing distance in the primary direction, the solution uses spatial arrangement and orientation in perpendicular directions to control field properties
3Device complexity
If the motor constant is assumed to be constant, then the control system is simplified, but overlay errors occur due to actual position-dependent variations
Solution Approach 1:
The magnet system is pre-configured with specific orientations and positions of subsidiary magnets relative to main magnets. This preliminary arrangement creates a inherently more uniform magnetic field that reduces motor constant variations, allowing simpler control systems to achieve better precision without complex real-time compensation
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 configuration reduces motor constant variations, increases positioning accuracy, and allows for a more efficient and precise force generation, leading to improved lithographic performance with reduced overlay errors.
Implementation Method 1
A force can be generated by the interaction between a current carried by the electrically conductive element and the magnetic field
Implementation Method 2
the first and second magnet assembly are arranged in Halbach configuration to provide a magnetic field of which at least a part is directed in the second direction
Data Source
AI summary
A lithographic apparatus includes an actuator for producing a force in a first direction between a first and a second part including a first magnet assembly and a second magnet assembly each attached opposite to each other to the first part of the apparatus, the first magnet assembly including a first main magnet system and a first outer subsidiary magnet system, and the second magnet assembly including a second main magnet system and a second outer subsidiary magnet system, the first and second main magnet system defining a space between them in a second direction perpendicular to the first direction. The actuator includes a coil attached to the second part. The distance between the first outer subsidiary magnet system and the second outer subsidiary magnet system in the second direction is substantially zero.