Lanthanated Tungsten Ion Source Corrosion Resistance
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Solution Overview
Problem
Conventional ion sources in ion implantation systems suffer from shortened lifetimes due to corrosion from volatile gases like fluorine, leading to premature failure and downtime, as they etch and damage internal components, particularly the cathode and repeller seals, resulting in instability and reduced ion beam performance.
Innovation Solution
The use of lanthanated tungsten and refractory metals alloyed with a rare earth metal in critical components such as the cathode, repeller, and arc chamber parts, which forms a stable oxide layer resistant to corrosion, eliminating the need for co-gases and reducing the formation of volatile tungsten fluorides and oxides, thereby protecting the ion source from corrosive gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional ion source materials (tungsten, molybdenum) are used, then the ion source can operate at high temperatures, but the volatile corrosive gases etch the cathode and repeller seals, shortening the useful lifetime
Solution Approach 1:
The patent applies composite materials by combining refractory metals (tungsten, molybdenum) with rare earth metals (lanthanum, cerium) to create lanthanated refractory metals. This composite material forms a protective oxide layer that resists etching by volatile corrosive gases while maintaining high temperature operation, thereby extending the useful lifetime of the ion source components.
Solution Approach 2:
The patent utilizes accelerated oxidation by allowing the refractory metal surface to oxidize in the presence of oxygen or water vapor, forming a stable oxide layer (such as lanthanum oxide or cerium oxide) that protects the underlying metal from further corrosion by fluorine-containing gases. This protective oxide layer prevents the etching of cathode and repeller seals.
2Device complexity
If conventional tungsten components are used, then the ion source structure is simple, but volatile tungsten fluorides and oxides form, causing ion beam instabilities
Solution Approach 1:
The patent replaces conventional tungsten with lanthanated refractory metals, which form stable oxide layers that prevent the formation of volatile tungsten fluorides and oxides. This maintains ion beam stability while keeping the ion source structure relatively simple, as it only requires changing the material composition of existing components.
Solution Approach 2:
The patent changes the chemical composition parameter of the refractory metal by adding rare earth metals (1-10% by weight of lanthanum or cerium). This parameter change transforms the material's chemical reactivity, preventing the formation of volatile fluorides and oxides that cause ion beam instabilities.
3Reliability
If co-gases are used to protect against corrosion, then the ion source components are protected, but the system complexity increases and additional gases are required
Solution Approach 1:
The patent applies self-service by designing the ion source components to protect themselves through the formation of stable oxide layers on the surface of the lanthanated refractory metals. This eliminates the need for external protective measures such as co-gases, thereby reducing gas system complexity while maintaining component protection.
Solution Approach 2:
The patent extracts the protective function from the gas system and integrates it directly into the ion source components themselves. By incorporating rare earth metals that form protective oxide layers, the components gain inherent corrosion resistance without requiring additional protective gases or complex gas management systems.
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 solution significantly extends the operational life of ion sources, enhances ion beam stability, and reduces downtime by preventing corrosion and the formation of conductive coatings that cause ion beam instabilities, while maintaining high temperature performance without the need for protective co-gases.
Implementation Method 1
forms a stable oxide layer resistant to corrosion
Implementation Method 2
A filament is supported within the tubular body and emits electrons that heat the endcap through electron bombardment, thereby thermionically emitting ionizing electrons into the gas confinement chamber
Data Source
AI summary
An ion implantation system is provided having one or more conductive components comprised of one or more of lanthanated tungsten and a refractory metal alloyed with a predetermined percentage of a rare earth metal. The conductive component may be a component of an ion source, such as one or more of a cathode, cathode shield, a repeller, a liner, an aperture plate, an arc chamber body, and a strike plate. The aperture plate may be associated with one or more of an extraction aperture, a suppression aperture and a ground aperture.