Ion Source Lifetime Extension via Hydrogen Co-Gas
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Solution Overview
Problem
Ion sources in ion implanters used for semiconductor fabrication suffer from efficiency reduction and poisoning due to the formation of tungsten and molybdenum oxides when using carbon-containing source gases like carbon dioxide or carbon monoxide, which react with free oxygen atoms, leading to decreased electron emission and shortened ion source lifetime.
Innovation Solution
Introducing a hydrogen co-gas to react with free oxygen ions generated during the ionization of carbon-containing source gases, forming water molecules and hydroxides that are removed by a vacuum pump, thereby reducing oxidation and maintaining beam current and extending ion source lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon-containing source gases (carbon dioxide or carbon monoxide) are used for carbon ion generation, then carbon implantation can be performed, but free oxygen atoms react with chamber materials (tungsten and molybdenum) to form oxides that poison the ion source and reduce its lifetime
Solution Approach 1:
A nitrogen-containing gas (ammonia, nitrogen trifluoride, or nitrogen) is introduced as an intermediary substance that reacts with free oxygen atoms to form nitrogen oxides. This intermediary prevents oxygen from directly reacting with and poisoning the ion source components, thereby maintaining ion source lifetime while enabling carbon implantation to continue
Solution Approach 2:
The harmful free oxygen atoms that would normally poison the ion source are converted into a beneficial role by having them react with the nitrogen-containing gas instead. The oxygen is effectively removed from the system through formation of nitrogen oxides, transforming the harmful oxygen into a participant in a controlled reaction that protects the ion source
2Reliability
If co-gas is introduced to relieve the destructive tendencies of free oxygen, then ion source lifetime is extended, but gas flow and pressure are added without adding usable precursor material
Solution Approach 1:
The type of co-gas is changed from traditional options (phosphine) to nitrogen-containing gases (ammonia, nitrogen trifluoride, or nitrogen). This parameter change provides multiple advantages: the gases are less toxic, can be introduced at lower flow rates, and the byproducts are easier to manage, thereby extending ion source lifetime while reducing operational 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
The use of hydrogen co-gas effectively removes oxygen ions, minimizing oxidation of ion source components and maintaining stable beam current and ion source performance, thereby increasing the lifetime of the ion source and improving implantation efficiency.
Implementation Method 1
Introducing a hydrogen co-gas to react with free oxygen ions generated during the ionization of carbon-containing source gases, forming water molecules and hydroxides
Implementation Method 2
forming water molecules and hydroxides that are removed by a vacuum pump
Implementation Method 3
react with the material from which the electrodes, the chamber liners, chamber body and arc slit are constructed. The chamber 102 will react with the free oxygen ions to form tungsten and molybdenum oxides
Data Source
AI summary
A system, apparatus and method for increasing ion source lifetime in an ion implanter are provided. Oxidation of the ion source and ion source chamber poisoning resulting from a carbon and oxygen-containing source gas is controlled by utilizing a hydrogen co-gas, which reacts with free oxygen atoms to form hydroxide and water.