Ion Source Tubular Cathode Single Slot Cold Plasma
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Solution Overview
Problem
Conventional hot-cathode ion sources face challenges in improving molecular ion beam currents, particularly for species like P2+ and BF2+, due to fragmentation of feed gases in hot plasma regions, leading to reduced formation of desired ion species.
Innovation Solution
An ion source with a tubular cathode featuring a single slot in a semi-cylindrical portion, positioned to direct feed gases into a cold plasma region, where they are ionized and collide with chamber surfaces, enhancing the formation of molecular ions by minimizing fragmentation and promoting thermal dissociation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hot-cathode ion sources are used to generate ion beams, then ion beam current can be achieved, but molecular ion beam currents (particularly P2+ and BF2+) are reduced due to fragmentation of feed gases in hot plasma regions
Solution Approach 1:
The invention changes the plasma temperature parameter from hot to cold by using a tubular cathode configuration with a slot that directs feed gases into a cold plasma region. This parameter change prevents fragmentation of molecular ions while still enabling ionization, thereby improving molecular ion beam currents of P2+ and BF2+ species
Solution Approach 2:
The tubular cathode is segmented into a front-facing semi-cylindrical portion with a slot and a rear-facing closed portion. This segmentation creates distinct functional zones: the slot region for cold plasma ionization and the closed rear portion for thermal management, preventing harmful fragmentation while maintaining ion generation
2Productivity
If feed gases are ionized in hot plasma regions, then ionization efficiency is improved, but formation of desired molecular ion species is reduced
Solution Approach 1:
The invention maintains ionization efficiency while changing the plasma temperature parameter to cold, enabling simultaneous formation of molecular ions. The slot in the tubular cathode creates a cold plasma region where molecular ions can form without fragmentation, resolving the contradiction between ionization efficiency and molecular ion formation
3Stability of the object's composition
If multiple slots are provided in the tubular cathode, then plasma distribution is improved, but device complexity increases
Solution Approach 1:
The tubular cathode is segmented into functional portions (front-facing with slot, rear-facing closed) rather than using multiple slots. This segmentation achieves stable plasma distribution through the single slot while maintaining structural simplicity, avoiding the complexity of multiple slots
Solution Approach 2:
The cathode uses an asymmetric design with a slot only in the front-facing semi-cylindrical portion while the rear-facing portion is closed. This asymmetric configuration optimizes plasma distribution toward the extraction region without requiring multiple slots, reducing device complexity
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 results in increased molecular ion beam currents and longer maintenance intervals, with improved throughput and efficiency by confining plasma within the tubular cathode and optimizing ion species formation.
Implementation Method 1
ionize a feed gas in a source chamber
Implementation Method 2
hot-cathode ion source utilizing an indirectly heated cathode (IHC)
Implementation Method 3
feed gases in hot plasma regions
Data Source
AI summary
An ion source including a chamber housing defining an ion source chamber and including an extraction plate on a front side thereof, the extraction plate having an extraction aperture formed therein, and a tubular cathode disposed within the ion source chamber and having a slot formed in a front-facing semi-cylindrical portion thereof disposed in a confronting relationship with the extraction aperture, wherein a rear-facing semi-cylindrical portion of the tubular cathode directed away from the extraction aperture is closed.