Electromagnetic Actuator Stray Field Compensation
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Solution Overview
Problem
Existing electromagnetic actuators in charged particle devices suffer from significant magnetic stray fields due to tolerance deviations in permanent magnetization and non-linear magnetic behavior of components, leading to inaccuracies and the need for mechanical couplings to prevent beam deflection, which limits operational speed and accuracy.
Innovation Solution
A method to optimize the allocation of permanent magnets in electromagnetic actuators by computing correlations between magnet positions and magnetic fields at predefined interference points, using finite element modeling and compensation magnets to minimize magnetic stray fields, allowing direct coupling to holding units and enhancing positional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electromagnetic actuators are used to move the holding unit, then operational speed and positioning accuracy are improved, but magnetic stray fields cause beam deflection due to the Lorentz force
Solution Approach 1:
The patent extracts and removes the harmful magnetic stray fields from the electromagnetic actuator by introducing compensation magnets that generate opposing magnetic fields. The compensation magnets are positioned and configured to cancel out the stray fields at critical locations, allowing the electromagnetic actuator to operate at high speeds without causing beam deflection.
Solution Approach 2:
The patent converts the harmful magnetic stray fields into a beneficial configuration by using compensation magnets to create a controlled magnetic field distribution. The stray fields that would normally cause beam deflection are transformed into a compensated field structure that enables both high-speed operation and beam stability through active magnetic field management.
2Object-affected harmful factors
If non-magnetic actuators such as piezo actuators are used, then beam deflection is minimized, but operational speed and positioning accuracy are reduced
Solution Approach 1:
The patent replaces the mechanical piezo actuator system with an electromagnetic actuator system that uses electromagnetic fields instead of mechanical deformation. By using Lorentz force generation through compensated electromagnetic actuators, the system achieves high-speed operation without the speed limitations of piezoelectric materials, while maintaining beam stability through active magnetic field compensation.
3Object-affected harmful factors
If a mechanical transmission is used between the holding unit and the linear motor, then the linear motor can be placed at a distance from the charged particle beam, but inaccuracies and inertia from the mechanical transmission reduce positioning accuracy
Solution Approach 1:
The patent extracts and eliminates the mechanical transmission components from the system by placing the electromagnetic actuator in direct contact with the holding unit. This removal of the mechanical transmission chain eliminates the sources of positioning inaccuracies and inertia, allowing the system to achieve high positioning accuracy while maintaining the linear motor at a safe distance from the charged particle beam through direct electromagnetic coupling.
4Ease of manufacture
If permanent magnets with tolerance deviations are used in the electromagnetic actuator, then manufacturing is simplified, but magnetic stray fields increase due to non-linear magnetic behavior
Solution Approach 1:
The patent implements a feedback-based magnetic field compensation system where the magnetic stray fields generated by permanent magnets with tolerance deviations are measured and actively compensated using additional magnets. The compensation magnets are positioned and configured based on feedback from magnetic field measurements, allowing the system to maintain low stray fields despite variations in permanent magnet manufacturing tolerances.
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 optimized allocation and compensation methods significantly reduce magnetic stray fields, enabling faster and more accurate movement of holding units in charged particle devices, improving the precision and speed of applications like SEM and electron beam lithography.
Implementation Method 1
an electrical supply will drive the electric coil as a result of which a magnetic interaction will take place
Implementation Method 2
This interaction can be in the form of a Lorentz force exerted on the coil by the magnetic field from the permanent magnets
Implementation Method 3
the second frame part has a plurality of predefined receiving positions for receiving a plurality of permanent magnets. By arranging the permanent magnets in the second frame part, a magnetic arrangement is obtained having an alternating pole pattern
Data Source
AI summary
The present invention is related to a method for fabricating an electromagnetic actuator. It is further related to an electromagnetic actuator and a charged particle device comprising such an actuator. According to the present invention, the method for fabricating is characterized by determining an optimal allocation of permanent magnets to reduce the magnetic stray field caused by deviations between the nominal and actual magnetization values of the permanent magnets. The invention further provides a charged particle device comprising an electromagnetic actuator fabricated using the method according to the invention.