Magnetic Scanner Ion Beam Zero-Field Effect Mitigation
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Solution Overview
Problem
Magnetic based ion beam scanners experience anomalous transport phases known as zero-field effects (ZFE) during periods of zero or close to zero magnetic field amplitudes, leading to irregular flux profiles and reduced beam current due to electron neutralization and cyclotron effects.
Innovation Solution
Applying constant magnetic fields at the entrance and exit of the magnetic scanner, in addition to an oscillatory time varying magnetic field, to maintain a non-zero magnetic field and mitigate the zero-field effect, thereby smoothing the flux profile and enhancing beam confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a magnetic scanner is used to scan the ion beam, then beam current delivery is improved and space-charge blowup is reduced, but zero-field effects cause anomalous transport phases and irregular flux profiles during periods of zero or close to zero magnetic field amplitudes
Solution Approach 1:
The patent applies a preliminary DC magnetic field to the ion beam before it enters the scanning region. This pre-applied field creates a baseline magnetic environment that prevents the beam from experiencing zero-field conditions during scanning, thereby anticipating and counteracting the zero-field effects before they can occur. The DC field serves as a preventive measure that maintains stable electron confinement throughout the scanning cycle.
Solution Approach 2:
The patent introduces a DC magnetic field as an intermediary field that mediates between the scanning RF field and the ion beam. This intermediary field provides continuous electron confinement by creating a persistent magnetic environment, while the RF scanning field operates on top of this baseline. The DC field acts as a buffer that prevents the scanning field from creating zero-field conditions, thus stabilizing the flux profile while allowing beam scanning to proceed.
2Ease of operation
If electric fields are used to scan the ion beam, then the beam path can be altered, but space-charge blowup occurs and limits the amount of beam current that can be delivered
Solution Approach 1:
The patent replaces the electric field-based scanning mechanism with a magnetic field-based scanning mechanism. Instead of using time-varying electric fields to deflect the ion beam, the system uses time-varying magnetic fields (RF scanning fields) applied in conjunction with a DC magnetic field. This substitution eliminates the space-charge blowup problem inherent in electric field scanning while maintaining the ability to control and alter the beam path for scanning applications.
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 approach prevents beam current fluctuations and maintains a stable flux profile, allowing for higher and more uniform ion beam current delivery during ion implantation, reducing the complexity of the beamline design and minimizing space-charge blowup.
Implementation Method 1
Mass analyzers typically employ a mass analysis magnet creating a dipole magnetic field to deflect various ions in an ion beam via magnetic deflection in an arcuate passageway which will effectively separate ions of different charge-to-mass ratios.
Implementation Method 2
A magnetic scanner generates a time varying magnetic field through which the ion beam passes. The time varying magnetic field diverts or alters the path of the ion beam such that after the scanner the ion beam appears to originate from a vertex point.
Implementation Method 3
One technique to account for the anomalous transport phase is to immerse the magnetic scanner into a secondary magnetic field to prevent electron motion... A constant magnetic field is applied to an ion beam about an entrance and/or exit of the magnetic scanner in order to mitigate the zero field effect
Data Source
AI summary
A magnetic scanner employs constant magnetic fields to mitigate zero field effects. The scanner includes an upper pole piece and a lower pole piece that generate an oscillatory time varying magnetic field across a path of an ion beam and deflect the ion beam in a scan direction. A set of entrance magnets are positioned about an entrance of the scanner and generate a constant entrance magnetic field across the path of the ion beam. A set of exit magnets are positioned about an exit of the scanner and generate a constant exit magnetic field across the path of the ion beam.