Ion Source Dopant Gas Mixture for Carbon Implantation
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Solution Overview
Problem
Ion source performance is compromised by the accumulation of carbon-based deposits and oxide deposits in ion implantation systems during carbon implantation, leading to beam glitching and reduced ion source life, necessitating frequent maintenance or replacement.
Innovation Solution
A dopant gas mixture comprising carbon monoxide and a fluorine-containing gas, such as carbon tetrafluoride, is used to reduce deposit accumulation and extend ion source life by ionizing to produce carbon ions and simultaneously self-clean the ion source surfaces, maintaining a high and uniform beam current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional dopant gases (CO2 or CO) are used for carbon implantation, then carbon ions can be generated for doping, but carbon-based deposits and oxide deposits accumulate on ion source surfaces and electrodes
Solution Approach 1:
The patent introduces a hydrogen-containing gas as an intermediary substance that mediates between the carbon-based dopant gas and the ion source surfaces. The hydrogen acts as a cleaning agent that reacts with carbon deposits and oxide deposits, converting them into volatile compounds that can be removed, thereby preventing accumulation while maintaining carbon ion generation capability
Solution Approach 2:
The patent changes the compositional parameters of the dopant gas by adding hydrogen-containing gas to the conventional CO2 or CO mixture. This parameter change transforms the gas chemistry to include species that can effectively clean deposits during the implantation process, resolving the contradiction between ion generation and deposit prevention
2Productivity
If dopant gas is used to generate ion beam, then carbon implantation can be performed, but beam glitching occurs due to deposits on electrodes
Solution Approach 1:
The hydrogen-containing gas serves as an intermediary that continuously cleans electrode surfaces during the implantation process, preventing the formation of deposits that would cause beam glitching. This maintains beam current stability and reliability throughout the production run
Solution Approach 2:
The patent implements continuous cleaning action by incorporating hydrogen-containing gas into the dopant mixture, allowing the ion source to maintain clean surfaces throughout the entire implantation process without interruption. This continuous action prevents beam glitching and maintains steady productivity
3Productivity
If ion source operates for extended periods, then productivity increases, but deposit accumulation degrades beam uniformity and requires maintenance shutdowns
Solution Approach 1:
The hydrogen-containing gas acts as a continuous cleaning intermediary that prevents deposit accumulation on extraction apertures and chamber surfaces during extended operation. This maintains beam uniformity and manufacturing precision throughout prolonged implantation cycles without requiring maintenance shutdowns
Solution Approach 2:
The patent enables continuous operation by implementing ongoing surface cleaning through the hydrogen-containing gas component. This continuous protective action prevents the degradation of beam uniformity that would otherwise necessitate maintenance interruptions, thereby extending productive run times
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 dopant gas mixture significantly reduces carbon-based and oxide deposits, minimizing beam glitching and extending ion source life, while maintaining a stable and uniform beam current for efficient carbon implantation processes.
Implementation Method 1
Ionization of the dopant gas generates the ion species which can be subsequently implanted into a given workpiece
Implementation Method 2
The fluorine-containing gas reacts with carbon deposits to form volatile carbon fluorides
Data Source
AI summary
A novel method and system for extending ion source life and improving ion source performance during carbon implantation are provided. Particularly, the carbon ion implant process involves utilizing a dopant gas mixture comprising carbon monoxide and one or more fluorine-containing gas with carbon represented by the formula CxFy wherein x≧1 and y≧1. At least one fluorine containing gases with carbon is contained in the mixture at about 3-12 volume percent (vol %) based on the volume of the dopant gas mixture. Fluoride ions, radicals or combinations thereof are released from the ionized dopant gas mixture and reacts with deposits derived substantially from carbon along at least one of the surfaces of the repeller electrodes, extraction electrodes and the chamber to reduce the overall amount of deposits. In this manner, a single dopant gas mixture provides carbon ions and removes problematic deposits typically encountered during carbon implantation.