Multi-axis Charged Particle Lens with Compensation Coil
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Solution Overview
Problem
Current charged particle beam systems face limitations in miniaturization due to the inability to sufficiently miniaturize magnetic lenses, leading to increased spacing between electron beams and reduced resolution, as well as aberrations caused by asymmetrical magnetic focusing fields.
Innovation Solution
A lens system comprising a common excitation coil and a compensation coil arranged between lens openings to provide a symmetrical magnetic flux, compensating for asymmetries and allowing for close packing of multiple charged particle beams, thereby reducing aberrations and achieving high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If magnetic lenses are miniaturized to reduce spacing between electron beams, then beam density increases, but the magnetic field cannot be arbitrarily increased limiting further miniaturization
Solution Approach 1:
Multiple individual excitation coils are merged into a single common excitation coil that surrounds all lens openings. This allows the magnetic field to be generated uniformly across multiple beams simultaneously, enabling closer spacing without requiring proportionally more magnetic field strength for each individual beam.
Solution Approach 2:
A compensation coil is introduced as an intermediary element to correct asymmetries in the magnetic flux distribution. This compensation coil generates additional magnetic flux that counteracts asymmetries caused by the common excitation coil geometry, enabling symmetric focusing fields even with compact lens arrangements.
2Device complexity
If a common excitation coil surrounds multiple lens openings, then device complexity is reduced, but asymmetry in magnetic flux distribution causes additional aberrations
Solution Approach 1:
A compensation coil is introduced as an intermediary element to correct asymmetries in the magnetic flux distribution. This compensation coil generates additional magnetic flux that counteracts asymmetries caused by the common excitation coil geometry, enabling symmetric focusing fields even with compact lens arrangements.
Solution Approach 2:
The magnetic flux distribution is adjusted by independently controlling the current in the compensation coil. By changing the current parameter in the compensation coil, the asymmetry in the total magnetic flux can be compensated to achieve symmetric focusing fields for all lens openings.
3Productivity
If lens openings are closely packed to increase beam density, then throughput increases, but asymmetry in magnetic flux distribution increases causing more aberrations
Solution Approach 1:
A compensation coil is introduced as an intermediary element to correct asymmetries in the magnetic flux distribution. This compensation coil generates additional magnetic flux that counteracts asymmetries caused by the common excitation coil geometry, enabling symmetric focusing fields even with compact lens arrangements.
Solution Approach 2:
The magnetic field generation is segmented into two independent functions: the common excitation coil provides the primary magnetic flux for all lenses, while the compensation coil provides localized correction flux for each lens opening. This segmentation allows independent optimization of each function.
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 solution enables close packing of multiple charged particle beams in a two-dimensional arrangement, enhancing throughput and achieving high resolution with reduced aberrations, making it suitable for applications requiring precise inspection and structuring at the micrometer or nanometer scale.
Implementation Method 1
a common excitation coil arranged around the plurality of lens openings for providing a respective first magnetic flux to the lens openings
Implementation Method 2
a compensation coil arranged between the lens openings for providing a respective second magnetic flux to at least some of the lens openings so as to compensate for an asymmetry of the first magnetic flux
Implementation Method 3
magnetic lenses, cannot be miniaturized sufficiently, since the magnetic field cannot be arbitrarily increased
Data Source
AI summary
A lens system for a plurality of charged particle beams comprises a lens body with a first pole piece, a second pole piece and a plurality of lens openings for the respective charged particle beams; a common excitation coil arranged around the plurality of lens openings for providing a respective first magnetic flux to the lens openings; and a compensation coil arranged between the lens openings for providing a respective second magnetic flux to at least some of the lens openings so as to compensate for an asymmetry of the first magnetic flux.