Cold-Field Emitter Extractor Self-Cleaning via Reversed E-Beam
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Solution Overview
Problem
Residual gas pressure in extreme ultra-high vacuum environments of electron-beam devices contaminates cold-field emission sources, shortens their lifetime, and introduces emission noise, despite baking out the extractor electrode, which is not sufficient to completely desorb molecules.
Innovation Solution
An e-beam device configuration with a cold-field emission source, extractor electrode, mirror electrode, and anode, where the extractor electrode is positively biased to extract electrons, and the mirror electrode is configurable to be positively or negatively biased to direct electrons back to the extractor electrode for self-cleaning through Desorption Induced by Electronic Transitions (DIET), effectively removing chemisorbed radicals and ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the extractor electrode is baked out to reduce outgassing, then the vacuum quality is improved, but molecules remain chemisorbed on the extractor electrode surfaces
Solution Approach 1:
The extractor electrode cleans itself by using the electron beam current to desorb chemisorbed molecules from its own surface. The electron beam, already present in the system for imaging, is directed onto the extractor electrode surface, providing continuous self-cleaning without requiring separate cleaning mechanisms or procedures.
Solution Approach 2:
The mechanical/thermal cleaning process (bakeout) is supplemented and enhanced by an electronic cleaning mechanism. Instead of relying solely on thermal energy from bakeout, the patent uses electron beam energy to desorb molecules, replacing the need for extended thermal processing with a more effective electronic desorption process.
2Productivity
If the extractor electrode is positively biased to extract electrons, then electron emission is improved, but chemisorbed radicals and ions accumulate on the extractor surface
Solution Approach 1:
The cleaning action is continuous and occurs simultaneously with electron extraction. As electrons are extracted from the cold field emission source and pass through the extractor electrode, they continuously desorb chemisorbed species from the extractor surface, ensuring the surface remains clean during operation rather than requiring periodic cleaning cycles.
Solution Approach 2:
The electron beam, which could potentially cause contamination or damage, is converted into a cleaning tool. The same electron current that is necessary for operation serves a dual purpose: extracting electrons for imaging while simultaneously cleaning the extractor electrode surface by desorbing chemisorbed species.
3Object-affected harmful factors
If bakeout is used to desorb molecules from the extractor electrode, then residual gas pressure is reduced, but complete desorption of chemisorbed molecules is not achieved
Solution Approach 1:
The cleaning mechanism changes the energy parameter from thermal (bakeout temperature) to electronic (electron beam energy). Instead of relying on thermal energy to desorb molecules, the patent uses high-energy electrons to directly interact with and desorb chemisorbed species, achieving more complete removal of contaminants.
Solution Approach 2:
The extractor electrode is cleaned in advance and continuously during operation, preventing the accumulation of chemisorbed layers. By maintaining a clean surface through continuous electron beam exposure, the system prevents contamination buildup rather than attempting to remove it after formation.
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 steady-state outgassing and contamination, extending the lifetime of the cold-field emission source and improving emission performance by continuously desorbing radicals and minimizing chemisorbed monolayer formation on the extractor electrode surfaces.
Implementation Method 1
a cold-field emission source to emit electrons and an extractor electrode to be positively biased with respect to the cold-field emission source to extract the electrons
Implementation Method 2
the mirror electrode is configurable to be positively or negatively biased to direct electrons back to the extractor electrode for self-cleaning through Desorption Induced by Electronic Transitions (DIET), effectively removing chemisorbed radicals and ions
Data Source
AI summary
An e-beam device includes a cold-field emission source to emit electrons and an extractor electrode to be positively biased with respect to the cold-field emission source to extract the electrons from the cold-field emission source. The extractor electrode has a first opening for the electrons. The e-beam device also includes a mirror electrode with a second opening for the electrons. The mirror electrode is configurable to be positively biased with respect to the extractor electrode during a first mode of operation and to be negatively biased with respect to the extractor electrode during a second mode of operation. The extractor electrode is disposed between the cold-field emission source and the mirror electrode. The e-beam device further includes an anode to be positively biased with respect to the extractor electrode and the cold-field emission source. The mirror electrode is disposed between the extractor electrode and the anode.