Butler Electrostatic Lens for Secondary Electron Angle Selection
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Solution Overview
Problem
Existing charged particle beam apparatuses struggle to efficiently detect charged particles emitted in specific directions due to mixed detection of particles emitted in various directions, leading to aberrations and difficulty in controlling the detection angle range, especially in wide emission angle regions.
Innovation Solution
The apparatus employs a Butler-type focusing lens with tapered electrodes and a Wien filter to control the detection angle range by maintaining a linear relationship between the focusing lens intensity and the arrival position of secondary electrons, allowing for selective detection of charged particles in desired emission angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional electrostatic lens is used to focus secondary electrons, then the detection efficiency is improved, but the detection angle range cannot be controlled and particles from various directions are detected in a mixed state
Solution Approach 1:
The electrostatic lens is divided into multiple electrode groups (first, second, third electrode groups) with different functions. The first electrode group focuses electrons, the second electrode group controls the detection angle range by adjusting potential, and the third electrode group corrects aberrations. This segmentation allows independent control of focusing and angle selection capabilities.
Solution Approach 2:
The electrostatic lens uses dynamically adjustable electrode potentials rather than fixed structures. By independently controlling the potential of each electrode group, the detection angle range and focusing characteristics can be adjusted in real-time to match different observation requirements, enabling dynamic adaptation to various detection scenarios.
2Productivity
If the detection angle range is widened to detect more secondary electrons, then the detection efficiency is improved, but the aberration increases and measurement precision deteriorates
Solution Approach 1:
A third electrode group is introduced as an intermediary element between the objective lens and the detector. This electrode group generates correcting electric fields that compensate for aberrations introduced when detecting electrons from wide angle ranges, thereby enabling high-efficiency wide-angle detection without sacrificing measurement precision.
3Measurement precision
If a passage opening limiting member is added to control the detection angle, then the detection angle range control is improved, but the device complexity increases
Solution Approach 1:
The electrostatic lens electrode groups serve multiple functions simultaneously: the first electrode group performs focusing, the second electrode group controls detection angle range, and the third electrode group corrects aberrations. This multi-functionality eliminates the need for separate passage opening limiting members, achieving angle control without increasing device complexity.
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 enables precise discrimination and detection of charged particles in specific directions, reducing aberrations and enhancing the controllability of the detection angle range, even in wide emission angle scenarios.
Implementation Method 1
an electrostatic lens including a plurality of electrodes disposed between the objective lens and the detector
Implementation Method 2
the electrostatic lens is a Butler type
Data Source
AI summary
Proposed is a charged particle beam apparatus for the purpose of detecting a charged particle emitted from a sample in a specific direction by discriminating between the charged particle and a charged particle emitted in another direction. As one aspect of achieving the above purpose, proposed is a charged particle beam apparatus including an objective lens configured to focus a beam emitted from a charged particle source, a detector (8) configured to detect at least one of a first charged particle (23) emitted from a sample by irradiating the sample with the beam and a second charged particle emitted from a charged particle collided member by causing the first charged particle to collide with the charged particle collision member disposed on a trajectory of the first charged particle, and an electrostatic lens (12) including a plurality of electrodes disposed between the objective lens and the detector, in which the electrostatic lens is a Butler type.