Extractor Electrode Curved Edge Minimizes Secondary Electrons
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Solution Overview
Problem
Conventional extractor designs in electron microscopy produce a large number of secondary electrons, which interact with the primary electron beam, preventing it from achieving a small spot size due to the large surface area exposed to the beam, especially when a magnetic lens is used for focusing.
Innovation Solution
The extractor electrode is designed with a frustoconical aperture that widens from the first surface to the second surface, featuring a curved edge with a radius of 5 µm to 50 µm and angled sidewalls from 5° to 75°, minimizing the surface area exposed to the electron beam and reducing secondary electron generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the extractor bore sidewalls present a large surface area to the primary electron beam, then the extractor can effectively extract electrons, but it generates a large number of secondary electrons that interact with the primary beam and prevent achieving a small spot size
Solution Approach 1:
The patent applies curvature by rounding the extractor bore edges with a specific radius of curvature (5-50 μm). This curved geometry reduces the effective surface area of the sidewalls that are exposed to the primary electron beam, thereby minimizing secondary electron generation while maintaining effective electron extraction through the bore aperture.
2Manufacturing precision
If a magnetic lens is used for focusing the primary beam, then the beam can be focused to a small spot size, but the magnetic field traps secondary electrons in the vicinity of the primary beam for a long time, degrading beam quality
Solution Approach 1:
The patent applies preliminary anti-action by designing the extractor bore with rounded edges to preemptively reduce secondary electron generation at the source. By minimizing the creation of secondary electrons before they enter the magnetic lens field, the system prevents the subsequent problem of secondary electron trapping that would otherwise degrade beam spot size and quality.
3Ease of manufacture
If the extractor upper surface has a large radius of curvature (e.g., 100 μm), then the manufacturing is easier, but the secondary electron generation is not effectively minimized
Solution Approach 1:
The patent applies parameter changes by specifying an optimized range for the radius of curvature (5-50 μm) that balances manufacturing feasibility with effective secondary electron suppression. This parameter optimization ensures the curvature is sufficient to minimize secondary electron generation while remaining practical for manufacturing processes.
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 design minimizes secondary electron generation, allowing for a smaller spot size and enabling the use of a strong magnetic lens without degradation by secondary electrons, thereby improving the performance of electron optical systems.
Implementation Method 1
The extractor may be configured to generate an electrostatic field at the emitter thereby causing electron emission and acceleration from the emitter into the rest of the electron source
Implementation Method 2
an electron source with an electron emitter, such as in a Schottky emission gun or a field emission gun, for producing an electron beam
Implementation Method 3
the extractor bore sidewalls presented a large surface area to the primary electron beam. Such a large surface area generated a large number of secondary electrons
Implementation Method 4
The electron beam may be used to produce a scanning probe or illuminate a sample or an aperture using a series of electron beam lenses, which may be magnetic or electrostatic
Implementation Method 5
The secondary electrons move more slowly than the primary electrons, and the magnetic field from the lens tends to trap them in the vicinity of the primary electron beam
Implementation Method 6
An electron optical column also typically includes an electrostatic pre-accelerator lens that focuses the electron beam
Data Source
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AI summary
Extractors and extractor systems minimize the generation of secondary electrons which interact with and degrade the primary electron beam. This can improve the performance of an electron beam system, such as a scanning electron microscope. The extractor may include a frustoconical aperture that widens as distance from the source of the electron beam increases. The entrance into the frustoconical aperture also can include a curved edge.