Ion Source Cleaning Endpoint Detection via Mass Spectrum Monitoring
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Solution Overview
Problem
Current methods for cleaning ion source chambers in ion implantation equipment require additional equipment for endpoint detection, such as Residual Gas Analyzers, which are not only cumbersome but also unable to detect ions created and extracted from the ion source, limiting the ability to utilize existing equipment for determining the completion of the cleaning process.
Innovation Solution
An apparatus and method utilizing a Faraday cup coupled with a mass analyzing magnet and current meter to detect the mass spectrum of ions extracted from the ion source chamber, allowing for endpoint detection of the cleaning process by monitoring the presence of chamber material in the ion beam, thereby determining when to stop the cleaning process using existing ion implantation system tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Residual Gas Analyzer or Optical Emission Spectroscopy is used for endpoint detection, then endpoint detection capability is achieved, but device complexity increases due to additional equipment
Solution Approach 1:
The ion implantation system performs endpoint detection using its own existing components (mass spectrometer and ion detector) rather than requiring separate dedicated equipment. The system uses the mass spectrometer already present in the ion implantation apparatus to analyze ions during the cleaning process, enabling self-service endpoint detection without additional external devices.
Solution Approach 2:
The mass spectrometer serves dual purposes: it functions as both a standard component for ion analysis in the ion implantation process and as an endpoint detection device for source chamber cleaning. This multi-functionality eliminates the need for separate dedicated endpoint detection equipment, reducing overall system complexity while maintaining detection capability.
2Measurement precision
If Residual Gas Analyzer is used for endpoint detection, then endpoint detection is achieved, but measurement precision is limited because it detects neutral gas atoms and molecules rather than ions from the ion source
Solution Approach 1:
The system uses its own ion detection capabilities through the mass spectrometer to monitor ions directly from the ion source during cleaning, rather than relying on external neutral particle detection. This allows the system to self-monitor the cleaning process using the same detection technology already optimized for ion analysis in the implantation process.
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 endpoint detection of the ion source cleaning process without additional equipment, ensuring the ion source chamber is thoroughly cleaned and preventing unstable source operation due to residual deposits.
Implementation Method 1
The ion source chamber 102 typically includes a heated filament which ionizes a feed gas introduced into the chamber to form charged ions and electrons (plasma)
Implementation Method 2
The mass analyzer is configured with a particular magnetic field such that only the ions with a desired mass-to-charge ratio are able to travel through the analyzer for maximum transmission through the mass resolving slit 107
Implementation Method 3
A Faraday cup is disposed downstream of the mass analyzing magnet and is configured to receive the ion beam. A current meter coupled to the Faraday cup is configured to provide a signal representative of the ions received by the Faraday cup
Data Source
AI summary
In an ion implanter, a Faraday cup is utilized to receive an ion beam generated during ion source cleaning. The detected beam has an associated mass spectrum which indicates when the ion source cleaning process is complete. The mass spectrum results in a signal composed of a cleaning agent and the material comprising the ion source. This signal will rise over time as the ion source chamber is being cleaned and will level-off and remain constant once the deposits are etched away from the source chamber, thereby utilizing existing implant tools to determine endpoint detection during ion source cleaning.