Plasma Probe Voltage Compensation for Conductive Film Buildup
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Solution Overview
Problem
Existing plasma measurement methods face challenges in accurately measuring the state of plasma due to the deposition of conductive deposition films on the probe device, which affects the accuracy of plasma electron temperature and ion density measurements.
Innovation Solution
A method is employed to measure the initial and operating plasma voltages, allowing for the derivation of the conductive deposition film voltage and subsequent subtraction to obtain the actual plasma voltage, thereby enabling accurate estimation of plasma state parameters despite the presence of conductive deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If plasma measurement is performed using a probe device in a plasma processing apparatus, then plasma state information can be obtained, but conductive deposition films are deposited on the probe device surface affecting measurement accuracy
Solution Approach 1:
The patent applies preliminary action by measuring the plasma voltage in an initial state before any conductive deposition film is formed on the probe device. This initial measurement serves as a reference value that is stored and later used to compensate for measurements taken after deposition occurs, thereby maintaining measurement accuracy throughout the probe's operational life.
Solution Approach 2:
The patent utilizes parameter changes by monitoring the voltage difference between the initial state and the current state of the probe device. As conductive deposition films accumulate on the probe surface, the electrical parameters (voltage) change, and this change is quantified and used to calculate compensation values that correct subsequent measurements, allowing continuous accurate plasma state monitoring.
2Productivity
If the probe device is used repeatedly for substrate processing and cleaning, then productivity is improved, but conductive deposition films accumulate on the probe surface degrading measurement precision
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage measurements from the probe device and comparing them against the stored initial voltage value. The system calculates the voltage difference and uses this feedback to determine compensation values that are applied to correct subsequent plasma measurements, ensuring accuracy is maintained throughout repeated substrate processing cycles.
Solution Approach 2:
The patent applies preliminary action by establishing a baseline measurement in the initial state before any deposition occurs. This preliminary measurement is stored and serves as the reference for all future compensation calculations, enabling the system to maintain measurement precision throughout the probe's operational lifecycle without requiring frequent recalibration or cleaning.
3Measurement precision
If conductive deposition film voltage is derived and subtracted from measurement voltage, then accurate plasma state estimation is achieved, but additional calculation steps increase system complexity
Solution Approach 1:
The patent applies mechanics substitution by replacing complex physical modifications to the probe device with computational methods. Instead of physically preventing deposition or frequently cleaning the probe, the system uses mathematical calculations (voltage subtraction and compensation) to correct measurement errors, thereby maintaining simplicity in the hardware while achieving high measurement accuracy through software-based compensation.
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 high accuracy in measuring plasma electron temperature and ion density by compensating for the effects of conductive deposition films, maintaining precise plasma state estimation even after repeated substrate processing and cleaning.
Implementation Method 1
a measurement circuit including a signal generator that outputs a fixed AC current
Implementation Method 2
measuring an initial plasma voltage by supplying the fixed AC current output by the measurement circuit to the plasma via the probe device
Data Source
AI summary
Provided is a plasma measurement method for measuring a state of plasma using a probe device provided in a plasma processing apparatus and a measurement circuit including a signal generator that outputs a fixed AC current, the method comprising: measuring an initial plasma voltage by supplying the fixed AC current to the plasma via the probe device, in a state where the plasma is generated in an initial state of the plasma processing apparatus; measuring a measurement voltage in an operating state by supplying the fixed AC current to the plasma via the probe device, in a state where the plasma is generated in the plasma processing apparatus in the operating state; deriving a conductive deposition film voltage by subtracting the initial plasma voltage from the measurement voltage; and deriving a plasma state using a plasma voltage obtained by subtracting the conductive deposition film voltage from the measurement voltage.