Planar Faraday Cup Ion Beam Current Measurement
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Solution Overview
Problem
Conventional Faraday cups in ion implantation systems have a limited cross-section area, leading to incomplete measurement of ion beam current, especially for larger workpieces and low-energy ion beams, resulting in reduced accuracy and the need for additional profilers to correct dosimetry, which increases costs and decreases throughput.
Innovation Solution
A planar Faraday cup and magnet device configuration that increases the cross-sectional area for ion beam measurement by suppressing secondary electrons and low-energy ions, allowing for complete ion beam reception and measurement without the need for additional profilers, by positioning the planar Faraday cup close to the chamber wall and using a magnet device to generate a magnetic field that contains undesired charged particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Faraday cup with limited cross-section area is used, then the chamber hardware remains compact and uncontaminated, but the ion beam current measurement becomes incomplete and inaccurate for larger workpieces and low-energy ion beams
Solution Approach 1:
The patent transitions from a conventional deep cylindrical Faraday cup to a planar Faraday cup configuration. This dimensional change allows the measurement surface to be extended in the plane perpendicular to the beam direction, significantly increasing the cross-sectional area available for capturing ion beam current while maintaining a compact depth profile that avoids chamber contamination issues.
Solution Approach 2:
The patent divides the Faraday cup measurement function into separate planar detection surfaces positioned at different locations. By segmenting the measurement function across multiple planar elements rather than relying on a single deep cup structure, the system achieves complete beam coverage without requiring excessive depth that would interfere with chamber hardware.
2Measurement precision
If the Faraday cup opening size is increased to capture more ion beam, then measurement completeness improves, but hardware interference and contamination from gas pipelines, power lines, and chamber walls increases
Solution Approach 1:
By adopting a planar configuration instead of a deep cylindrical structure, the patent distributes the measurement surface across a large area in the plane rather than concentrating it in depth. This allows the Faraday cup to capture complete ion beam current without extending deeply into the chamber where gas pipelines, power lines, and chamber walls would cause interference and contamination.
Solution Approach 2:
The patent introduces planar detection surfaces as intermediary elements between the ion beam and the chamber hardware. These planar surfaces serve as the measurement interface, allowing complete beam capture while maintaining physical separation from contaminating hardware components that would otherwise be in direct path or close proximity.
3Measurement precision
If a profiler is added to measure and correct ion beam current distribution, then dosimetry accuracy improves, but hardware cost and operation complexity increase while throughput decreases
Solution Approach 1:
The patent enables the Faraday cup system to self-correct by using the planar configuration's inherent ability to capture complete beam current distribution. The system serves its own correction need through the geometric design of the planar surfaces, which naturally account for beam expansion and distribution without requiring external profiler equipment or complex correction algorithms.
Solution Approach 2:
The patent extracts the beam current measurement function from the conventional deep cup design and relocates it to planar surfaces. This extraction allows the measurement system to inherently capture complete beam distribution by design, eliminating the need for separate profiler equipment and complex post-processing corrections.
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 configuration enables precise and accurate measurement of ion beam current, improving dosimetry control and reducing hardware costs by allowing for real-time, precise measurement of ion beam current without the need for additional profilers, while maintaining chamber design constraints.
Implementation Method 1
The magnet device is located close to the planar Faraday cup. Therefore, by properly adjusting the magnet field applied by the magnet device around the planar Faraday cup, all of secondary electrons, incoming electrons and low energy ions may be adequately suppressed.
Data Source
AI summary
Techniques for ion beam current measurement, especially for measuring low energy ion beam current, are disclosed. In one exemplary embodiment, the techniques may be realized as an ion beam current measurement apparatus has at least a planar Faraday cup and a magnet device. The planar Faraday cup is close to an inner surface of a chamber wall, and may be non-parallel to or parallel to the inner surface. The magnet device is located close to the planar Faraday cup. Therefore, by properly adjusting the magnetic field, secondary electrons, incoming electrons and low energy ions may be adequately suppressed. Further, the planar Faraday cup may surround an opening of an additional Faraday cup being any conventional Faraday cup. Therefore, the whole ion beam may be received and measured well by the larger cross-section area of at least the planar Faraday cup on the ion beam path.