Retarding Field Analyzer Electrode Shielding Stray Fields
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Solution Overview
Problem
Retarding field analyzers in charged particle beam devices face challenges in achieving high energy resolution and precise voltage/material contrast sensitivity, particularly when placed near a high-voltage beam tube, as the stray field regions increase, affecting the primary charged particle beam and requiring improved electrode designs to minimize distortions and maintain energy resolution.
Innovation Solution
The introduction of additional electrode elements, such as ring electrodes and high-ohmic electrodes, which electrically shield the retarding field region from the beam tube element, reduce stray field regions, and ensure coplanarity/concentricity of equipotential lines, allowing for high energy resolution measurements even in close proximity to the primary charged particle beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the retarding field analyzer is placed near the high-voltage beam tube element, then the device can operate with compact design and high throughput, but the stray field regions increase and affect the primary charged particle beam
Solution Approach 1:
The patent introduces additional electrode elements (ring electrodes and high-ohmic electrodes) as intermediary components between the beam tube element and the retarding field analyzer. These electrodes act as mediators that create electrical shielding, blocking the harmful stray fields from the high-voltage beam tube while allowing the retarding field analyzer to operate in close proximity for compact design.
2Measurement precision
If additional electrode elements are added to shield the retarding field region, then the energy resolution is maintained, but the device complexity increases
Solution Approach 1:
The patent divides the shielding function into multiple segmented electrode elements: ring electrodes that provide radial shielding and high-ohmic electrodes that provide longitudinal shielding. This segmentation allows each electrode element to perform a specific shielding function, maintaining energy resolution through coordinated operation while enabling modular design and easier adjustment compared to a single complex shielding structure.
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 the retarding field analyzer to operate with high energy resolution and precision, reducing stray field regions and minimizing interference with the primary charged particle beam, thus enhancing the accuracy of voltage and material contrast measurements.
Implementation Method 1
The first voltage V1 is more negative than the second voltage V2 in order to provide a retarding electric field 6 within the retarding electric field region 20 that decelerates incoming electrons 2
Implementation Method 2
Charged particles that have a sufficient energy, however, overcome the potential barrier and are detected by a charged particle detector
Implementation Method 3
The accelerating electric field 12 serves to accelerate the electrons in order to increase the detection efficiency of the electron detector 8
Data Source
AI summary
The invention provides a charged particle beam device to inspect or structure a specimen with a primary charged particle beam propagating along an optical axis; a beam tube element having a tube voltage; and a retarding field analyzer in the vicinity of the beam tube element to detect secondary charged particles generated by the primary charged particle beam on the specimen. According to the invention, the retarding field analyzer thereby comprises an entrance grid electrode at a second voltage; at least one filter grid electrode at a first voltage; a charged particle detector to detect the secondary charged particles; and at least one further electrode element arranged between the entrance grid electrode and the at least one filter grid electrode. The at least one further electrode element reduces the size of the stray fields regions in the retarding electric field region to improve the energy resolution of the retarding field analyzer. The improvement of the energy resolution is significant, in particular when the beam tube element is part of a high voltage beam tube.