Planar Faraday Cup Ion Beam Current Measurement
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Solution Overview
Problem
Conventional Faraday cups in ion implantation systems face challenges in accurately measuring ion beam current due to misalignment, beam expansion, and limited size, leading to inaccuracies and increased hardware costs when trying to enhance measurement accuracy.
Innovation Solution
A planar Faraday cup with a voltage assembly is positioned adjacent to the chamber wall, increasing the cross-sectional area for ion beam reception and suppressing unwanted charged particles with an electric field, allowing for more accurate and efficient measurement of ion beam current without the need for additional hardware or profilers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the Faraday cup opening is increased to receive more of the ion beam, then the measurement accuracy is improved, but the hardware cost and device complexity increase due to chamber modifications
Solution Approach 1:
The patent transitions from a conventional deep Faraday cup with a limited opening to a planar Faraday cup that extends in a different dimension (perpendicular to the beam path) along the chamber wall. This dimensional change allows the measurement surface to be much larger without increasing the opening size, thereby receiving more of the expanded ion beam while avoiding chamber modifications and reducing device complexity
2Measurement precision
If magnets are added near the Faraday cup to suppress unwanted charged particles, then measurement accuracy is improved, but hardware cost and device complexity increase
Solution Approach 1:
The patent replaces the mechanical/magnetic suppression system (magnets) with an electric field-based suppression system. By applying a voltage to the planar Faraday cup, an electric field is created that repels unwanted charged particles (electrons and ions) while allowing the measurement of the ion beam current, thereby achieving the same suppression function without adding magnetic components
3Measurement precision
If a profiler is used to measure ion beam distribution for correction, then measurement accuracy is improved, but hardware cost and operation complexity increase
Solution Approach 1:
The patent extracts and eliminates the need for the profiler by designing a planar Faraday cup that directly receives the entire expanded ion beam profile. Instead of measuring a portion of the beam and applying computational corrections, the cup's large planar surface area allows it to capture the full beam distribution, making the profiler unnecessary and simplifying the measurement system
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 proposed solution significantly increases the measurement accuracy of ion beam current by receiving a larger portion of the beam and minimizing the impact of undesired charged particles, particularly for low-energy ion beams, while reducing hardware costs and complexity.
Implementation Method 1
a voltage assembly electrically coupled with the planar Faraday cup and used to apply electric voltage to the planar Faraday cup
Implementation Method 2
a planar Faraday cup located close or adjacent to an inner surface of a chamber wall... for measuring an ion beam current
Data Source
AI summary
Techniques for measuring ion beam current, especially for measuring low energy ion beam current, are disclosed. The technique may be realized as an ion beam current measurement apparatus having at least a planar Faraday cup and a voltage assembly. The planar Faraday cup is located close to an inner surface of a chamber wall, and intersects an ion beam path. The voltage assembly is located outside a chamber having the chamber wall. Therefore, by properly adjusting the electric voltage applied on the planar Faraday cup by the voltage assembly, some undesired charged particles may be adequately suppressed. Further, the planar Faraday cup may surround an opening of a non-planar Faraday cup which may be any conventional Faraday cup. Therefore, the whole ion beam may be received and measured well by the larger cross-section area of the planar Faraday cup on the ion beam path.