Aberration Corrector Segmentation for Low-Energy Electron Beam Precision
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Solution Overview
Problem
Existing chromatic-and-spherical aberration correctors for low-energy charged particle beam systems, such as SEMs, face complexity in mechanical structure and higher power source stability requirements due to the use of complex electromagnetic quadrupoles, making them difficult to maintain and operate accurately.
Innovation Solution
The solution involves separating the complex electromagnetic multipole into individual electrostatic and magnetic multipoles, arranging them symmetrically and antisymmetrically with respect to a center plane, and positioning them differently along the electron beam path to simplify the mechanical structure and reduce power source stability requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex electromagnetic quadrupoles are used for chromatic aberration correction, then chromatic aberration correction effectiveness is improved, but mechanical structure complexity increases and power source stability requirements become more stringent
Solution Approach 1:
The patent divides the complex electromagnetic quadrupole into separate electrostatic and magnetic quadrupole components. These segmented components are arranged in a simplified mechanical structure with the electrostatic quadrupole positioned upstream of the magnetic quadrupole, reducing mechanical complexity while maintaining chromatic aberration correction effectiveness through their combined optical action.
Solution Approach 2:
The patent introduces an intermediary arrangement where electrostatic and magnetic quadrupoles are positioned at different locations along the electron beam path. The electrostatic quadrupole serves as an intermediary element that works in conjunction with the magnetic quadrupole to achieve chromatic aberration correction with relaxed power source stability requirements.
2Measurement precision
If complex electromagnetic quadrupoles are used for chromatic aberration correction, then chromatic aberration correction effectiveness is improved, but power source stability requirements increase
Solution Approach 1:
The patent segments the chromatic aberration correction function into separate electrostatic and magnetic quadrupole components. This segmentation allows each component to be driven by less stringent power sources, reducing the overall power source stability requirement from 10^-7 to approximately 10^-8 while maintaining effective chromatic aberration correction through the combined action of both quadrupoles.
3Volume of moving object
If multiple multipoles are arranged closely together, then compact design is achieved, but assembly accuracy becomes more difficult to maintain
Solution Approach 1:
The patent segments the aberration corrector into distinct electrostatic and magnetic quadrupole units with clear spatial separation. The electrostatic quadrupole is positioned upstream with its optical axis coincident with the magnetic quadrupole's optical axis downstream. This segmented arrangement maintains compact overall design while improving assembly accuracy by reducing the complexity of precise alignment between multiple closely-spaced multipoles.
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 simplifies the mechanical structure, improves assembly accuracy, and reduces the required power source stability by 40% to 50%, achieving stable chromatic aberration correction while maintaining high resolving power.
Implementation Method 1
a first electric field generated by the first electrostatic multipole
Implementation Method 2
a first magnetic field generated by the second magnetic multipole
Implementation Method 3
a first field in which a first electric field generated by the first electrostatic multipole and a first magnetic field generated by the second magnetic multipole are superimposed on each other
Data Source
AI summary
High expectations are placed on aberration correctors to increase the resolving power of charged particle devices. Meanwhile, a far more complicated configuration and higher mechanical precision assembly in comparison to prior art aberration correctors are necessary in charged particle beam optical devices that use low-energy electron beams. A complex electromagnetic quadrupole part employed in the aberration corrector preferably has the forward extremities of the poles provided in a vacuum near an electron beam path and excitation coils disposed outside the vacuum, and this necessitates a structure that can achieve both electrical insulation and vacuum sealing for each of these poles. Such structural complexity generally conflicts with improving mechanical assembly precision. The complicated structure in the above problems can be simplified by: separating the electrodes and the magnetic poles in the complex electromagnetic multipole that had been used in prior art aberration correctors; and offsetting the positions of both, or ensuring that the widths of both do not match. Consequently, improvement of mechanical assembly precision can be achieved.