TOF Ion Sensor for Angular Distribution Monitoring
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Solution Overview
Problem
Current ion implantation techniques lack the ability to accurately measure ion energy, angular distribution, and mass, which are crucial for achieving predictable and repeatable process results in semiconductor manufacturing.
Innovation Solution
A time-of-flight (TOF) ion sensor system that includes a drift tube and detector, capable of varying its angle with respect to the substrate plane, allowing for the measurement of ion species' mass and energy as a function of angle, and featuring a deceleration potential to resolve high-energy ions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Faraday cup is used to measure implant dose, then total charge can be measured, but it cannot distinguish between different charged particles or provide insight into plasma composition
Solution Approach 1:
The patent replaces the simple Faraday cup mechanical measurement system with a time-of-flight mass spectrometer that uses electromagnetic fields and time measurement to identify ion species. The TOF-MS measures the time it takes for ions to travel through a field-free drift region, allowing differentiation of ion masses while maintaining measurement capability.
Solution Approach 2:
The patent introduces a time-of-flight drift tube as an intermediary between the plasma source and detector. This drift tube allows ions of different masses to separate based on their flight times, serving as a mediator that enables species identification without requiring direct interaction between the detector and complex plasma environment.
2Measurement precision
If conventional beamline tools are used for ion implantation, then ions can impinge on workpiece over wide range of angles, but there is no capability to measure angular distribution of ions
Solution Approach 1:
The patent makes the TOF-MS sensor rotatable about the substrate normal axis, allowing dynamic adjustment of the measurement angle. This enables the sensor to scan through different angular positions and map the angular distribution of ion flux without requiring a fixed complex multi-angle sensor array.
Solution Approach 2:
The patent designs a single TOF-MS sensor that can perform multiple functions: measuring ion mass, measuring ion energy, and measuring angular distribution by rotation. This universal sensor replaces what would otherwise require multiple specialized measurement devices.
3Loss of information
If time-of-flight sensor is used to monitor ion species, then ion mass information can be obtained, but ion energy and angular distribution information are not provided
Solution Approach 1:
The patent measures ion energy by varying the deceleration potential applied to ions before they enter the drift tube. By changing this parameter and measuring the corresponding time-of-flight, the system can determine ion energy while maintaining the same physical sensor hardware.
Solution Approach 2:
The patent uses rotation of the sensor assembly to dynamically change the measurement angle, allowing a single sensor to map angular distribution. This dynamic approach avoids the complexity of having fixed sensors at multiple angular positions simultaneously.
4Loss of time
If high voltage sheath is used to accelerate ions toward target, then ion implantation can be achieved, but time-resolved measurements of plasma are required for pulsed processing
Solution Approach 1:
The patent synchronizes the TOF-MS measurements with the pulsed plasma cycle by gating the ion extraction to specific phases of the plasma pulse. This allows time-resolved measurement of ion species during different phases of the pulsed process without requiring continuous measurement that would slow down production.
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 real-time monitoring and control of ion parameters, providing detailed implantation profiles and allowing for adjustments to plasma parameters, thereby enhancing process uniformity and predictability.
Implementation Method 1
a time-of-flight sensor to monitor at a fixed angle the plasma species including ions that may impinge on a substrate
Implementation Method 2
the ion detector is configured to detect the packets of ions derived from the pulse of ions and corresponding to respective different ion masses
Implementation Method 3
ions that are attracted from the plasma across the plasma sheath may implant into the workpiece
Data Source
AI summary
A time-of-flight (TOF) ion sensor system for monitoring an angular distribution of ion species having an ion energy and incident on a substrate includes a drift tube wherein the ion sensor system is configured to vary an angle of the drift tube with respect to a plane of the substrate. The drift tube may have a first end configured to receive a pulse of ions from the ion species wherein heavier ions and lighter ions of the pulse of ions arrive in packets at a second end of the drift tube. An ion detector may be disposed at the second end of the ion sensor, wherein the ion detector is configured to detect the packets of ions derived from the pulse of ions and corresponding to respective different ion masses.