Ion Beam Scan Distance Calibration Using Faraday Cups
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Solution Overview
Problem
Current ion beam processing techniques for substrates, such as semiconductor wafers, often result in over or under scanning due to estimated beam edge measurements, leading to non-uniform implantation and inefficient use of beam current.
Innovation Solution
The use of Faraday cups positioned on opposite sides of the wafer to measure actual beam currents, allowing for the determination of an optimal scan distance to ensure complete coverage of the wafer diameter, thereby optimizing beam current utilization and ensuring uniform implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If beam edge estimation is used to determine scan distance, then the system complexity is reduced, but the manufacturing precision deteriorates due to over or under scanning
Solution Approach 1:
The patent replaces mechanical/physical measurement methods with electrical measurement methods. Faraday cups measure beam current electrically to determine beam edges and scan distance, substituting for complex mechanical measurement systems while achieving precise scan distance determination through electrical signal detection
Solution Approach 2:
The patent introduces Faraday cups as intermediary measurement devices positioned at wafer edges. These cups serve as mediators that detect beam current and provide feedback signals to the control system, enabling precise scan distance determination without direct mechanical measurement of the beam itself
2Ease of operation
If estimated beam edge is used for scan distance, then the ease of operation is improved, but the reliability deteriorates due to non-uniform implantation
Solution Approach 1:
The patent implements a feedback control system where Faraday cups continuously measure beam current at wafer edges during scanning. The control system uses this feedback to dynamically adjust scan distance parameters, ensuring reliable and uniform implantation while maintaining ease of operation through automated control
Solution Approach 2:
The patent performs preliminary beam edge localization using Faraday cups before the actual implantation scan. This preliminary measurement establishes accurate scan distance parameters in advance, ensuring reliable implantation uniformity while keeping the main implantation process simple and automated
3Manufacturing precision
If actual beam current measurement is performed using Faraday cups, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical measurement systems with electrical measurement using Faraday cups. Beam current is measured electrically to determine beam edges and scan distance, achieving high manufacturing precision through simpler electrical sensing rather than complex mechanical measurement apparatus
Solution Approach 2:
The patent makes the Faraday cup measurement system multi-functional. The same Faraday cups used for beam edge localization are also used for beam current monitoring and dose measurement during implantation, reducing overall system complexity while maintaining high scan distance accuracy
4Productivity
If scan distance is optimized based on beam current measurements, then the productivity is improved through uniform implantation, but the loss of time increases due to additional measurement steps
Solution Approach 1:
The patent performs beam edge localization and scan distance optimization as preliminary actions before production implantation. This one-time calibration establishes accurate scan parameters that enable high-speed uniform implantation thereafter, improving productivity while minimizing time loss through efficient preliminary setup
Solution Approach 2:
The patent maintains continuous useful action by using the same Faraday cup measurement system for both calibration and production monitoring. The measurement system remains in place and continues to provide useful data during implantation for dose monitoring and process control, eliminating the need for separate measurement equipment and reducing overall time loss
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 ensures the ion beam is sufficiently scanned over the entire wafer diameter, minimizing wasted beam current and achieving accurate dose monitoring, leading to more efficient and uniform ion implantation processes.
Implementation Method 1
measuring a first beam current of the ion beam at the first Faraday cup position and measuring a second beam current of the ion beam at the second Faraday cup position
Data Source
AI summary
Provided herein are approaches for optimizing a full horizontal scanned beam distance of an accelerator beam. In one approach, a method may include positioning a first Faraday cup along a first side of an intended beam-scan area, positioning a second Faraday cup along a second side of the intended beam-scan area, scanning an ion beam along the first and second sides of the intended beam-scan area, measuring a first beam current of the ion beam at the first Faraday cup and measuring a second beam current of the ion beam at the second Faraday cup, and determining an optimal scan distance of the ion beam across the intended beam-scan area based on the first beam current and the second beam current.