Pulse Plasma Probe Sampling Mask Period
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Solution Overview
Problem
In plasma processing apparatuses that alternate high frequency power ON and OFF, variations in measurement signals due to changing power levels lead to inaccurate calculation of electrical parameters, as detection values are significantly affected by sampling timing.
Innovation Solution
A plasma processing apparatus that samples measurement signals after a preset mask period from the ascending timing of a pulse signal until its descending timing, selecting the last sample values as detection values, which are stable when the power reaches a stable level, and adjusts the number of sample values based on switching frequency to maintain consistent output timing across varying frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high frequency power is applied in pulse shape with ON and OFF switching, then plasma sheath can be extinguished and electric charges can be neutralized, but measurement signals vary greatly with sampling timing leading to inaccurate electrical parameter calculation
Solution Approach 1:
The patent applies preliminary action by introducing a mask period before sampling to allow the pulse signal to stabilize. The sampling is performed only after the mask period has elapsed, ensuring that measurements are taken when the signal has reached a stable state, thereby eliminating timing-dependent variations in measurement accuracy
Solution Approach 2:
The patent uses feedback by continuously monitoring the pulse signal levels and adjusting the sampling timing accordingly. The system detects when the pulse signal reaches stable levels and triggers sampling at these specific moments, creating a closed-loop control mechanism that ensures accurate electrical parameter calculation regardless of pulse timing variations
2Ease of operation
If sampling is performed at regular cycle continuously, then detection is simple, but detection values vary significantly depending on sampling timing in pulse-shaped power application
Solution Approach 1:
The patent applies dynamics by making the sampling operation adaptive rather than static. Instead of fixed regular sampling, the system dynamically adjusts sampling timing based on the actual pulse signal state, performing sampling only when stability criteria are met. This dynamic approach maintains operational simplicity while dramatically improving detection value stability
3Measurement precision
If mask period is introduced to wait for stable power level, then measurement accuracy improves, but response time and productivity decrease
Solution Approach 1:
The patent applies parameter changes by optimizing the mask period duration based on the specific pulse characteristics and processing requirements. The mask period is set to the minimum necessary time to achieve signal stability, balancing measurement accuracy with processing speed. This parameter optimization ensures that the system achieves sufficient measurement precision without unnecessary delays that would reduce productivity
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 reduces variations in detection values dependent on sampling timing, ensuring accurate calculation of electrical parameters and maintaining consistent output timing regardless of changing switching frequencies.
Implementation Method 1
a high frequency power supply configured to generate a high frequency power and turn the high frequency power ON and OFF
Implementation Method 2
a probe detector configured to measure electrical characteristics on the power transmission line and generate measurement signals
Implementation Method 3
plasma of the processing gas is generated in a high frequency electric field formed between an upper electrode and a lower electrode
Data Source
AI summary
A plasma processing apparatus includes a high frequency power supply turning a high frequency power ON/OFF and supplying the high frequency power to either one of upper and lower electrodes. A matching circuit and a power transmission line are provided between the high frequency power supply and the either one of the electrodes. A probe detector measures electrical characteristics on the power transmission line and generates measurement signals. A processing unit samples the measurement signals, generates sample values, The processing unit receives a pulse signal corresponding to ON/OFF switching of the high frequency power, generates sample values by sampling the measurement signals at a sampling interval for a period after the lapse of a mask period from an ascending timing thereof until a descending timing thereof, and selects sample values obtained through the last one or more sampling with respect to the descending timing, as detection values.