Electron Gun Aperture Layout for Cation Deflection and Cathode Protection
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Solution Overview
Problem
The generation of cations (positive ions) due to electron collisions with gas molecules in the electron gun of an electron beam writing apparatus leads to cathode damage, affecting electron beam current distribution and increasing the risk of electric discharge.
Innovation Solution
The electron gun design includes an anode electrode with multiple openings at different positions and a Wehnelt electrode at a negative potential, combined with a limiting aperture substrate, to redirect cations away from the cathode and reduce the risk of discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If exhaust paths are formed in the anode electrode to reduce cation generation, then cation flow to cathode is reduced, but electric discharge risk increases due to positive potential tubular members
Solution Approach 1:
The anode electrode is segmented into multiple independent opening structures instead of a single exhaust path. Multiple openings are distributed across the anode electrode surface, allowing cations to be exhausted through different locations. This segmentation reduces the probability of electric discharge by distributing the positive potential regions, while still effectively removing cations through the collective action of multiple exhaust paths.
Solution Approach 2:
Different regions of the anode electrode are given different functions through the opening configuration. The openings are strategically positioned to create localized electric field distributions that guide cations away from the cathode while maintaining appropriate potential distributions. This local quality variation allows the system to reduce cation flow without creating uniform high-discharge-risk regions.
2Productivity
If cations are not exhausted, then electron beam current distribution is maintained, but cathode crystal damage occurs reducing beam emission
Solution Approach 1:
The harmful cations are extracted and removed from the electron beam path through the exhaust openings in the anode electrode. The openings allow cations to be pulled away from the region between the cathode and anode, preventing them from reaching and damaging the cathode crystals. This extraction mechanism protects cathode durability while maintaining electron beam current distribution through proper potential control.
Solution Approach 2:
The anode electrode acts as an intermediary structure between the cathode and the vacuum chamber. It mediates the interaction between electrons and cations by providing exhaust paths that selectively remove cations while allowing electrons to pass through to form the electron beam. This intermediary function protects the cathode from direct cation exposure.
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 effectively reduces cathode damage and enhances electron beam current distribution by redirecting cations, improving the electron gun's performance and reducing the risk of electric discharge.
Implementation Method 1
a cathode configured to emit an electron beam
Implementation Method 2
a Wehnelt electrode arranged between the cathode and the anode electrode, configured to be applied with a relatively negative potential with respect to a potential of the anode electrode
Implementation Method 3
at least one second opening at a position different from a position of the first opening, the at least one second opening being formed in a same surface as the first opening, and maintained at a relatively positive potential with respect to a potential of the cathode
Data Source
AI summary
An electron gun includes a cathode to emit electron beams, an anode configured to include a surface which faces the cathode and in which there are formed the first opening for passing the electron beams from the cathode and at least one second opening at a position different from that of the first opening and in the same surface as the first opening, and maintained to be a relatively positive potential with respect to a cathode potential, a limiting aperture substrate at the downstream side of the anode with respect to an advancing direction of the electron beams, formed with the third opening for passing the electron beams and limiting passage of a portion of the electron beams, and a Wehnelt electrode between the cathode and the anode, applied with a relatively negative potential with respect to an anode potential.