Charged-Particle Source Back-Sputtering for In-Situ Emitter Cleaning
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Solution Overview
Problem
Existing charged-particle sources for multi-beam tools face inefficiencies in cleaning the emitter electrode surface due to contamination, as conventional cleaning methods are ineffective when the source is operational and require disassembly.
Innovation Solution
A charged-particle source with adjustment electrodes and a pressure regulator device that allows for in-situ cleaning by ionizing gas particles within the source space, using secondary electrons to direct ionized gas particles onto the emitter surface for sputtering or etching, and an optional gas ionizer to generate a plasma for enhanced cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cleaning methods are used to clean the emitter electrode surface, then the source can be cleaned, but the source must be disassembled and cleaning is only possible before operation
Solution Approach 1:
The system enables self-service cleaning by using the charged particle beam itself to generate secondary electrons that ionize gas molecules, creating ions that automatically clean the emitter surface through back-sputtering. The cleaning process is integrated into the operational cycle, requiring no external disassembly or separate cleaning equipment.
Solution Approach 2:
The system performs preliminary cleaning actions by maintaining a controlled gas atmosphere in the source space that continuously generates cleaning ions before significant contamination accumulates. The pressure regulator device and gas supply system prepare the cleaning environment in advance, allowing cleaning to occur during operational intervals rather than requiring shutdowns.
2Productivity
If the source operates continuously to maintain productivity, then output is maximized, but contamination accumulates on the emitter surface reducing performance
Solution Approach 1:
The system maintains continuous useful action by integrating the cleaning function into the operational cycle. During beam operation, secondary electrons continuously ionize the gas atmosphere, creating a steady stream of cleaning ions that continuously clean the emitter surface. This eliminates the need to stop production for cleaning, as the cleaning action occurs concurrently with beam generation.
Solution Approach 2:
The system changes operational parameters by controlling gas pressure and composition in the source space. The pressure regulator device maintains optimal gas pressure to ensure sufficient ionization while preserving vacuum conditions for beam operation. This parameter control allows the system to simultaneously maintain high productivity and emitter cleanliness through dynamic adjustment of gas flow and pressure.
3Productivity
If gas pressure is increased to enhance ionization for cleaning, then cleaning efficiency improves, but vacuum quality deteriorates
Solution Approach 1:
The system optimizes the gas pressure parameter to a specific range that balances ionization efficiency with vacuum quality. The pressure regulator device maintains gas pressure at levels sufficient to generate adequate secondary electron ionization for effective cleaning, while keeping the absolute pressure low enough to preserve vacuum conditions for charged particle beam operation. This precise parameter control resolves the contradiction between cleaning efficiency and vacuum maintenance.
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
Enables efficient and controlled cleaning of the emitter surface without disassembly, improving the homogeneity and reliability of the source by adjusting ionization rates and trajectories of charged particles, thus maintaining the source's performance and extending its operational lifespan.
Implementation Method 1
secondary electrons generated by charged particles at the counter electrode ionize particles of said gas fed into the source space, producing ionized gas particles
Implementation Method 2
electrostatic potentials are applied to at least some of the adjustment electrodes, generating an electric field directing these ionized gas particles onto the emitter surface
Implementation Method 3
a first cleaning mode, where a gas is held at a pre-defined pressure value within the source space, while applying a voltage between the emitter and counter electrodes, wherein secondary electrons generated by charged particles at the counter electrode ionize particles of said gas fed into the source space
Data Source
Figure 1~1a
Figure 2
Figure 3~4b
AI summary
A charged-particle source (100) for emission of electrons or other electrically charged particles comprises, located between the emitter electrode (101) having an emitter surface (111) and a counter electrode (103), at least two adjustment electrodes (106, 107, 108, 109); a pressure regulator device (104) is configured to control the gas pressure in the source space (110) at a pre-defined pressure value. In a first cleaning mode of the particle source (100), applying a voltage between the emitter and counter electrodes (101, 103) directs gas particles towards the counter electrode (103), generating secondary electrons which ionize particles (161) of the gas in the source space, and electrostatic potentials are applied to at least some of the adjustment electrodes (106-109), generating an electric field directing the ionized gas particles (161) onto the emitter surface (111).