Plasma Probe Measurement Using Phase Feedback Voltage Control
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Solution Overview
Problem
Current plasma measuring methods lack accuracy in maintaining constant voltage applied to plasma, leading to inconsistencies in plasma state measurement due to deposits and changing capacitance components in the measuring circuit.
Innovation Solution
A plasma measuring method using a probe device and measuring circuit that applies AC voltage and measures current phases to adjust and maintain a constant voltage applied to the plasma, allowing for accurate plasma state measurement by vector calculation and adjustment of AC voltage based on phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional plasma measuring methods are used, then measurement can be performed, but measurement precision deteriorates due to changing capacitance components and deposits
Solution Approach 1:
The patent implements feedback control by measuring the phase difference between the current flowing through the plasma and the AC voltage, then using this information to adjust the AC voltage to maintain constant plasma voltage. This closed-loop feedback mechanism compensates for changing capacitance components and deposits, ensuring consistent and accurate plasma state measurements throughout the processing period.
Solution Approach 2:
The patent changes the measurement approach by introducing phase difference measurement and vector calculation as new parameters. Instead of relying solely on current magnitude, the system measures both the magnitude and phase of the current, then performs vector calculation to determine the plasma voltage. This parameter expansion enables accurate measurement despite changing capacitance conditions.
2Measurement precision
If AC voltage is applied to measure plasma current, then plasma state can be measured, but voltage applied to plasma becomes unstable due to changing capacitance
Solution Approach 1:
The system uses feedback control where the measured phase difference between plasma current and AC voltage is used to adjust the AC voltage amplitude. This ensures that the voltage actually applied to the plasma remains constant despite changes in circuit capacitance caused by deposits or plasma condition changes, thereby maintaining stable and accurate plasma current measurements.
Solution Approach 2:
The patent introduces dynamic adjustment of the AC voltage based on real-time phase difference measurements. The system continuously monitors the phase relationship between voltage and current, and dynamically modifies the voltage amplitude to compensate for changing capacitance conditions, maintaining stable plasma voltage throughout the measurement period.
3Ease of operation
If simple current measurement is performed, then measurement process is simple, but measurement precision deteriorates due to capacitance effects
Solution Approach 1:
The patent introduces phase difference measurement as an intermediary parameter that mediates between the simple current measurement and the actual plasma state. By measuring the phase relationship between voltage and current, the system creates an intermediate calculation step (vector calculation) that eliminates the distorting effects of capacitance, thereby achieving accurate plasma state measurement while maintaining operational simplicity.
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 method ensures accurate and consistent plasma state measurement by maintaining a constant plasma voltage, reducing errors caused by deposits and changing capacitance, thereby improving the reliability of plasma processing outcomes.
Implementation Method 1
measuring a second current in the measuring circuit when the AC current voltage is outputted from the signal transmitter to the probe device in a state where plasma is generated in the plasma processing apparatus
Implementation Method 2
measuring a phase difference between a current flowing through the plasma and the AC voltage by vector calculation using the measured first current and the measured second current
Data Source
AI summary
Provided is a plasma measuring method for measuring a plasma state using a probe device disposed at a plasma processing apparatus and a measuring circuit including a signal transmitter that outputs an AC voltage, the method comprising: measuring a first current in the measuring circuit when the AC voltage is outputted from the signal transmitter to the probe device in a state where plasma is not generated in the plasma processing apparatus and a second current in a state where plasma is generated in the plasma processing apparatus; measuring a phase difference between a current flowing through the plasma and the AC voltage by vector calculation using the measured first and second currents; and adjusting the AC voltage such that a voltage applied to the plasma becomes constant based on the phase difference and measuring a plasma state based on the measured current flowing through the plasma.