Electron Gun Shield Electrode Stabilizes Beam Current
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Solution Overview
Problem
The existing Schottky emission electron guns experience irregular minute discharges, leading to fluctuations in electron beam current, which deteriorate spatial resolution and reproducibility, making it difficult to predict and correct the issue in high spatial resolution observations.
Innovation Solution
A charged particle beam device with an electron gun configuration that includes a tip, a suppressor, an extraction electrode, an insulator, and a conductive metal between the suppressor and the extraction electrode, where a voltage lower than the tip voltage is applied to the conductive metal to prevent minute discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large current is emitted by the SE electron gun to increase throughput and reduce observation time, then productivity is improved, but minute discharge occurs irregularly causing current fluctuation and spatial resolution deterioration
Solution Approach 1:
A conductive metal layer is introduced as an intermediary between the suppressor and the extraction electrode. This intermediate layer mediates the electric field distribution, preventing direct discharge between the high-voltage tip and the extraction electrode while maintaining the large current emission capability. The conductive metal acts as a buffer that stabilizes the current flow.
Solution Approach 2:
The invention changes the electrical parameters by applying a specific voltage (lower than the tip voltage) to the conductive metal layer. This voltage parameter adjustment creates a controlled potential gradient that prevents irregular discharge while allowing large current emission, thus resolving the contradiction between productivity and reliability.
2Productivity
If a large current is emitted to achieve high brightness and short observation time, then productivity is improved, but spatial resolution deteriorates due to minute discharge
Solution Approach 1:
The conductive metal layer serves as an intermediary that smooths the electric field distribution, preventing the irregular minute discharge that would otherwise degrade spatial resolution. This allows the system to maintain high current emission (for speed) while preserving image quality.
Solution Approach 2:
The conductive metal layer helps create a more uniform potential distribution in the electron gun structure. By reducing potential gradients that cause irregular discharge, it maintains stable electron beam emission, thereby preserving spatial resolution during high-speed observation.
3Reliability
If the conductive metal is provided between the suppressor and the extraction electrode with a lower voltage, then minute discharge is reduced and current stability is improved, but device complexity increases
Solution Approach 1:
The electron gun structure is segmented into distinct functional layers: the tip, the suppressor, the conductive metal layer, and the extraction electrode. This segmentation allows each component to perform its specific function independently, with the conductive metal layer specifically tasked with stabilizing the electric field and preventing discharge.
Solution Approach 2:
The electron gun employs a composite structure combining different materials with specific properties: the suppressor (typically conductive), the conductive metal layer (providing controlled conductivity and voltage distribution), and the extraction electrode. This composite approach optimizes performance while managing the added complexity through functional integration.
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 stabilizes the emission of a large current electron beam, reducing minute discharges and maintaining high spatial resolution and reproducibility in charged particle beam devices.
Implementation Method 1
A voltage lower than a voltage of the tip is applied to the conductive metal
Implementation Method 2
a fairly small discharge (hereinafter, referred to as a minute discharge) occurs irregularly many times
Implementation Method 3
An example of an electron gun that emits such an electron beam includes a Schottky emission electron gun
Data Source
AI summary
A large current electron beam is stably emitted from an electron gun of a charged particle beam device. The electron gun of the charged particle beam device includes: a SE tip 202; a suppressor 303 disposed rearward of a distal end of the SE tip; a cup-shaped extraction electrode 204 including a bottom surface and a cylindrical portion and enclosing the SE tip and the suppressor; and an insulator 208 holding the suppressor and the extraction electrode. A shield electrode 301 of a conductive metal having a cylindrical portion 302 is provided between the suppressor and the cylindrical portion of the extraction electrode. A voltage lower than a voltage of the SE tip is applied to the shield electrode.