Plasma Diagnostic System Using Capacitance Sensing
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Solution Overview
Problem
Current plasma diagnosing techniques, such as the Langmuir probe, face challenges in accurately measuring plasma characteristics in real-time due to signal distortion and interference, especially when dealing with mixture gases or materials deposited on the probe, which hinders precise process control in semiconductor and solar cell manufacturing.
Innovation Solution
A plasma diagnosing system that generates a signal with a frequency non-overlapping with the plasma discharge frequency, using a capacitance or impedance measuring unit with electrode pairs and a protective circuit to limit signal magnitude and filter noise, allowing for real-time monitoring of plasma density through changes in capacitance or impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a plasma frequency probe (Langmuir probe) is used to measure plasma characteristics, then plasma density can be measured, but the probe causes interference with the plasma and signal distortion occurs
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the electrode and plasma. This dielectric layer allows the electrode to sense plasma characteristics (capacitance/impedance changes) without direct contact with the plasma, thereby eliminating probe interference and signal distortion while maintaining measurement capability
Solution Approach 2:
The patent replaces the traditional direct-contact mechanical probe system with a capacitive/impedance sensing system using electrode-dielectric-plasma configuration. This substitution eliminates the mechanical interference of the probe in plasma while enabling indirect measurement of plasma characteristics through electrical parameter changes
2Measurement precision
If a probe is used during plasma deposition process, then plasma characteristics can be monitored, but material deposits on the probe blocking the information signal
Solution Approach 1:
The dielectric layer serves as a protective intermediary that prevents plasma deposition materials from directly contacting and blocking the electrode. The electrode measures capacitance/impedance changes through the dielectric layer, which remains unaffected by material deposition, thus maintaining continuous plasma signal transmission
Solution Approach 2:
The patent segments the probe structure into distinct functional layers: electrode, dielectric layer, and plasma interface. This segmentation isolates the electrode from direct plasma exposure and material deposition, allowing the measurement function to remain unaffected by deposition processes
3Adaptability or versatility
If a plasma frequency probe is used with mixture gas discharge, then plasma can be generated, but accurate plasma density diagnosis becomes difficult
Solution Approach 1:
The patent replaces the frequency-based Langmuir probe measurement system with a capacitance/impedance sensing system. This substitution enables accurate plasma density diagnosis in mixture gas discharges by measuring the reactive component of the plasma impedance, which remains reliable even when plasma frequency varies due to different gas compositions
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 accurate, real-time plasma monitoring and diagnosis, improving process yield and reliability in semiconductor and display industries by compensating for abnormal plasma discharging states, thus enhancing the precision of semiconductor manufacturing.
Implementation Method 1
a capacitance measuring unit which includes an electrode to which at least a part of plasma generated in the plasma generating device is deposited and the generated signal is applied and measures an electric signal in the electrode
Data Source
AI summary
The present invention relates to a plasma diagnosing system and method, and more particularly, to a system and a method for diagnosing plasma in real time using a change in a capacitance sensed by an electrode using a reference waveform having a frequency different from a plasma discharging frequency band region. The sensed capacitance varies before and after discharging plasma and the plasma is diagnosed using the change in capacitance in real time.