Plasma Matching Reactance Control for Impedance Stability
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Solution Overview
Problem
In capacitively coupled plasma processing, high frequency power modulation introduces impedance changes that challenge matching device operations, leading to instability and component lifespan issues, especially at high pulse frequencies and wider duty ratio ranges, making it difficult to achieve stable and accurate matching.
Innovation Solution
A plasma processing method that includes a sampling-average-value calculating process, moving-average-value calculating process, and reactance control to match impedance by controlling the reactance element in the matching device, allowing for accurate impedance matching during both on and off periods of high frequency power modulation, even at high pulse frequencies and extended duty ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high frequency power modulation is applied to plasma generation, then charging damage is suppressed and process reliability is improved, but impedance changes cause matching device instability and reduced component lifespan
Solution Approach 1:
The matching device employs dynamic adjustment of reactance elements that track and adapt to the time-varying impedance characteristics of the plasma load during power modulation cycles, maintaining stability despite changing operating conditions
Solution Approach 2:
The system uses feedback control where the actual impedance of the plasma load is continuously monitored and used to adjust the matching network parameters, ensuring stable operation under modulated power conditions
2Reliability
If high pulse frequency modulation is used to reduce charging damage, then process stability is improved, but matching device operation becomes difficult and component lifespan is reduced
Solution Approach 1:
The matching device is designed to operate in synchronization with the periodic power modulation cycles, adjusting its parameters at appropriate phases of the modulation waveform to handle high pulse frequencies without excessive stress on components
Solution Approach 2:
The system pre-adjusts matching network parameters in anticipation of impedance changes during power modulation cycles, reducing transient stresses and protecting components from damage that would occur with reactive adjustments
3Adaptability or versatility
If wide duty ratio range is implemented for power modulation, then process versatility is improved, but matching accuracy deteriorates
Solution Approach 1:
The matching network uses dynamic parameter adjustment that adapts to different duty ratios in real-time, maintaining accurate impedance matching across the full range of modulation conditions through continuous optimization
Solution Approach 2:
The system changes multiple parameters of the matching network simultaneously (reactance values, coupling coefficients) to maintain optimal matching accuracy across varying duty ratios and power modulation conditions
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 configuration enables stable and accurate matching operations with high reproducibility, reducing fundamental frequency reflection waves and extending the lifespan of matching device components, even at high pulse frequencies and wider duty ratios.
Implementation Method 1
Electrons are accelerated by a high frequency field generated between the two facing electrodes by applying the high frequency power, and plasma is generated as a result of ionization by collision between the electrons and a processing gas
Implementation Method 2
a reactance control process of controlling a reactance of the reactance element such that the measurement value of the load impedance obtained from the load impedance-measurement-value calculating process is equal or approximate to a preset matching point corresponding to impedance on the side of the first high frequency power supply
Data Source
AI summary
A plasma processing method for performing a plasma process on a substrate in a plasma processing apparatus is provided. The plasma processing method comprises: a sampling-average-value calculating process of sampling voltage detection signals and electric current detection signals and calculating an average value of these signals during a first monitoring time; a moving-average-value calculating process of calculating a moving average value of the voltage detection signals and the electric current detection signals; a load impedance-measurement-value calculating process of calculating a measurement value of a load impedance with respect to a first high frequency power supply; and a reactance control process of controlling a reactance of a variable reactance element such that the measurement value of the load impedance is equal or approximate to a preset matching point corresponding to impedance on the side of the first high frequency power supply.