Optical Calibration of RFEA Sensors Without Plasma Re-Exposure
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Solution Overview
Problem
Retarding field energy analyzer (RFEA) sensors used in plasma processing operations suffer from rapid degradation due to plasma environments, leading to inaccurate measurements and costly, time-consuming recalibration processes, which are further exacerbated when multiple RFEAs are used on a single sensor substrate.
Innovation Solution
An optical calibration system is employed to measure optical transmission through RFEAs, correlating it to ion transmission, allowing for faster, less expensive, and less damaging recalibration by using a light source and photonic detector to determine a scaling factor that aligns optical transmission values with reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RFEA sensors are used in plasma processing operations, then plasma properties can be measured, but the sensors degrade rapidly leading to inaccurate measurements
Solution Approach 1:
The patent creates an optical copy of the ion transmission measurement process by using a light source and photodetector to measure optical transmission through the RFEA sensor. This optical measurement serves as a surrogate for the actual ion transmission measurement, allowing calibration without exposing the sensor to plasma. The optical transmission data is then correlated to ion transmission data through scaling factors, enabling accurate plasma property measurement while preserving sensor integrity.
Solution Approach 2:
The patent introduces an intermediary calibration process that uses optical transmission measurements as a mediator between the light source and the final ion transmission measurements. This intermediary optical measurement system allows calibration of the RFEA sensor without direct plasma exposure, acting as a protective buffer that transfers calibration information optically rather than through plasma interaction.
2Measurement precision
If traditional plasma-based recalibration is performed, then measurement accuracy can be restored, but the process is time-consuming and costly
Solution Approach 1:
The patent replaces the mechanical/plasma-based recalibration system with an optical measurement system. Instead of using plasma to recalibrate the sensor (which requires vacuum chambers, plasma generation equipment, and lengthy procedures), the invention uses light transmission measurements that can be performed rapidly at atmospheric pressure. This substitution of the recalibration mechanism dramatically reduces both time and cost while maintaining measurement accuracy through optical-to-ion transmission correlation.
3Adaptability or versatility
If multiple RFEA sensors are used on a single sensor substrate, then more plasma properties can be monitored, but degradation and recalibration complexity increase
Solution Approach 1:
The patent creates a universal calibration approach that can be applied to all RFEA sensors on a substrate simultaneously. The optical transmission measurement system serves as a multi-functional tool that can calibrate multiple sensors through a single measurement process, rather than requiring separate plasma-based recalibration for each sensor. This universal optical calibration method reduces the complexity of managing multiple sensors while maintaining the ability to monitor diverse plasma properties.
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 optical calibration system enables quick and accurate recalibration of RFEAs, reducing technician training requirements and extending sensor lifespan while maintaining measurement precision without exposing the sensors to plasma environments.
Implementation Method 1
measuring a reference transmission value of an amount of light from the light source that is transmitted through the reference sensor towards the photonic detector
Data Source
AI summary
Some embodiments described herein relate to a method of calibrating a device sensor that includes inserting a reference sensor into a calibration system. In an embodiment, the calibration system includes a light source, and a photonic detector. In an embodiment, the method further includes measuring a reference transmission value of an amount of light from the light source that is transmitted through the reference sensor towards the photonic detector, and inserting the device sensor into the calibration system. In an embodiment, the method further includes measuring a transmission value of the amount of light from the light source that is transmitted through the device sensor towards the photonic detector, and calculating a scaling factor for the device sensor. In an embodiment, the scaling factor equalizes the transmission value of the device sensor to the reference transmission value of the reference sensor.