Electron Gun Aperture Coating for Flare Suppression

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Solution Overview

Problem

In electron guns, a flare occurs due to secondary electrons generated at the aperture on the extracting electrode, leading to reduced resolution and signal-to-noise in electron microscope images, which existing technologies fail to address effectively.

Innovation Solution

The electron gun is configured with apertures on the extracting electrode, where the surface of the base material is coated with a material having a low secondary electron emission rate, such as carbon or boron, and the potential of the apertures is set equal to the extracting electrode's potential to minimize secondary electron generation and passage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional aperture on the extracting electrode is used, then the electron beam can be extracted and accelerated, but secondary electrons are generated at the aperture causing flare that reduces image resolution and signal-to-noise ratio

Engineering Contradiction:

Improveimage resolutionVSAvoidsecondary electron generation

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the material parameter of the aperture surface by coating it with low secondary electron emission rate materials (such as carbon, boron, or their compounds). This parameter change reduces the secondary electron emission rate to 0.6 or less, thereby suppressing flare generation while maintaining the aperture's function of extracting and accelerating the electron beam

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite structure where a base material (such as tungsten or molybdenum) is coated with a low secondary electron emission rate material layer (such as carbon or boron). This composite material approach combines the structural integrity of the base material with the low secondary electron emission properties of the coating layer

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If the aperture surface is coated with low secondary electron emission rate material, then flare is suppressed and image quality improves, but the device structure and manufacturing process become more complex

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidaperture structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent modifies the surface property parameter of the existing aperture by applying a coating layer, rather than redesigning the entire aperture structure. This approach improves signal-to-noise ratio by suppressing flare while adding minimal structural complexity - only a thin coating layer is required

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The low secondary electron emission rate material acts as an intermediary layer between the electron beam and the aperture base material. This coating layer mediates the interaction by reducing secondary electron generation while allowing the electron beam to pass through the aperture opening

Inventive Principle:

Principle #24Intermediary (Mediator)

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 significantly reduces secondary electron generation, suppressing flare occurrence and enabling high-resolution, high-signal-to-noise images in electron microscopy, while eliminating system peaks during analysis.

Implementation Method 1

a surface of a base material of at least an aperture closest to the electron source is coated with a material having a secondary electron emission rate of 0.6 or less when irradiation energy of primary electrons colliding against the aperture ranges from 2 to 3 kV

Methodology Applied

Scientific EffectSecondary electron emission: Photoelectric Effect

Implementation Method 2

an extracting electrode configured to apply an electric field to the electron source for extracting electrons from the electron source

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 3

an accelerating electrode configured to accelerate electrons extracted using the extracting electrode at a predetermined accelerating voltage

Methodology Applied

Scientific EffectElectrostatic acceleration: Electric Field

Data Source

PatentUS9293293B2Electron gun and charged particle beam device having an aperture with flare-suppressing coating

Publication Date: 2016.03.22 HITACHI HIGH TECH CORP

AI summary

The objective of the present application is to suppress the occurrence of flares and to reduce the amount of secondary electrons arising at an aperture provided to the lead-out electrode of an electron gun. By coating a thin film having a low rate of secondary electron emission such as carbon onto the aperture of a lead-out electrode closest to an electron source in an electron gun, it is possible to reduce the amount of secondary electrons arising. Secondary electrons arising at the lead-out electrode, are reduced, and so as a result, flare is reduced. By incorporating two apertures to the lead-out electrode, and applying to the two apertures a potential that is equipotential to the lead-out electrode, it is possible to eliminate an electric field from seeping from under to over the lead-out electrode. Secondary electrons arising when an electron beam impacts the lead-out electrode cease to incur force in the direction of passage from the lead-out electrode, and consequently there is a reduction in flares.