Aberration Corrector Line Cross Position Control
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Solution Overview
Problem
In charged particle beam apparatuses like scanning electron microscopes, magnetic interference between pole stages of the aberration corrector leads to anisotropy in the resolution and depth of focus on the sample surface, hindering accurate inspection and measurement, especially when observing fine patterns.
Innovation Solution
A charged particle beam apparatus with a correction system that includes multiple stages of multipoles, a line cross position control device, optical axis control, image shift amount extraction, and feedback determination to adjust quadrupole field excitation amounts, ensuring the line cross position aligns with the center and maintaining uniform aperture angle and optical magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the aberration corrector is miniaturized to reduce device size, then the distance between multipoles is shortened, but magnetic interference between pole stages increases causing line cross position deviation and anisotropy
Solution Approach 1:
The patent implements a feedback control mechanism where the line cross position is detected and fed back to adjust the quadrupole field excitation amounts. This closed-loop system compensates for position deviations caused by magnetic interference, ensuring the line cross position aligns with the optical axis center even in miniaturized configurations.
Solution Approach 2:
The patent dynamically adjusts the excitation amounts of quadrupole fields as control parameters to compensate for magnetic interference effects. By changing these electrical parameters based on detected position deviations, the system maintains proper line cross alignment without requiring physical redesign of the compact structure.
2Measurement precision
If multiple stages of multipoles are used to correct aberration, then resolution is improved, but magnetic interference between stages causes anisotropy in aperture angle and optical magnification
Solution Approach 1:
The system uses feedback control to detect anisotropy in aperture angle and optical magnification caused by magnetic interference between multipole stages. The detected deviations are fed back to adjust the excitation amounts of individual quadrupole fields, compensating for the anisotropic effects while preserving the high-resolution capability provided by multiple aberration correction stages.
Solution Approach 2:
The patent applies different excitation amounts to different quadrupole field stages based on their specific positions and functions within the multipole system. This localized adjustment allows each stage to contribute optimally to aberration correction while compensating for local magnetic interference effects, maintaining overall optical uniformity.
3Stability of the object's composition
If the intensities of quadrupole fields are adjusted to align line cross position, then anisotropy is reduced, but additional control complexity is introduced
Solution Approach 1:
The patent employs an automated feedback control system that measures line cross position deviations and automatically calculates the required adjustments to quadrupole field excitation amounts. This eliminates the need for manual adjustment and reduces operational complexity, as the system self-regulates to maintain optical uniformity.
Solution Approach 2:
The system performs self-diagnosis and self-correction by detecting its own optical uniformity deviations and automatically adjusting the quadrupole field excitations accordingly. This self-service capability reduces the need for external intervention and simplifies the overall control process despite the multiple adjustment parameters involved.
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 approach reduces or eliminates anisotropy in the charged particle beam on the sample surface, enabling high-resolution and high-precision imaging even with magnetic interference, by aligning the line cross position and adjusting quadrupole field intensities to maintain uniform optical conditions.
Implementation Method 1
The aberration corrector is configured with plural stages of multipole lenses and generates an electric field or a magnetic field to eliminate aberration contained in a charged particle beam
Implementation Method 2
The aberration corrector is configured with plural stages of multipole lenses and generates an electric field or a magnetic field to eliminate aberration
Implementation Method 3
due to the magnetic interference between the stages of the poles configured with a magnetic material, the center in the z direction of multipole deflection fields, the center in the z direction of the quadrupole fields, and the center in the z direction of the poles do not coincide with each other
Data Source
AI summary
In order to provide an aberration correction system that realizes a charged particle beam of which the anisotropy is reduced or eliminated on a sample surface even in the case where there is magnetic interference between pole stages of an aberration corrector, an correction system includes a line cross position control device (209) which controls a line cross position in the aberration corrector of the charged particle beam so that a designed value and an actually measured value of the line cross position are equal to each other, an image shift amount extraction device (210), and a feedback determination device (211) which determines whether or not changing an excitation amount of the aberration corrector is necessary whether or not changing an excitation amount is necessary from an extracted image shift amount.