Plasma RF Frequency Control for Reflected Wave Reduction
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Solution Overview
Problem
Existing plasma processing apparatuses face challenges in reducing the power level of reflected waves of source radio-frequency power, which can lead to inefficiencies and potential damage.
Innovation Solution
A plasma processing apparatus equipped with sensors to measure reflected wave power and phase differences, allowing for frequency control to adjust the source radio-frequency power based on these measurements to minimize reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the source radio-frequency power is increased to improve plasma generation efficiency, then the plasma density increases, but the reflected wave power level increases causing potential damage and inefficiency
Solution Approach 1:
The patent applies periodic modulation to the bias radio-frequency power, alternating between a first power level and a second power level at a modulation frequency. This periodic action creates time-varying plasma impedance that can be exploited to reduce reflected wave power while maintaining average plasma generation efficiency, directly resolving the contradiction between productivity and harmful reflected waves
Solution Approach 2:
The patent changes the bias power level parameter dynamically between two distinct levels (first power level and second power level) to control plasma impedance. By adjusting these power levels and the modulation frequency, the system optimizes the balance between plasma generation efficiency and reflected wave reduction, addressing the technical contradiction through parameter optimization
2Object-generated harmful factors
If the bias radio-frequency power level is modulated to reduce reflected wave power, then the reflected wave power level decreases, but the complexity of the power supply control system increases
Solution Approach 1:
The control system implements periodic modulation of the bias radio-frequency power between two discrete levels, which can be achieved through relatively simple switching circuitry. This periodic control strategy reduces reflected wave power while maintaining manageable system complexity through the use of straightforward modulation techniques
Solution Approach 2:
The system dynamically adjusts the bias power level between two states based on feedback from reflected wave power measurements. This dynamic control enables the system to adapt to changing plasma conditions and minimize reflected waves while using a control architecture that balances complexity with effectiveness through phase-locked loop technology
3Object-generated harmful factors
If the modulation frequency of the bias radio-frequency power is increased to improve reflected wave reduction, then the reflected wave power level decreases, but the difficulty of synchronizing with the plasma response increases
Solution Approach 1:
The patent employs feedback control where the modulation frequency is adjusted based on the phase difference between the modulated bias power and the reflected wave power. By detecting this phase difference and using it to tune the modulation frequency to the plasma's resonant response, the system achieves effective reflected wave reduction while automatically synchronizing with plasma dynamics, thereby reducing the perceived synchronization difficulty
Solution Approach 2:
The system uses periodic modulation at frequencies that match the plasma's natural response characteristics. By operating at these resonant frequencies, the system maximizes the effectiveness of reflected wave reduction while the periodic nature provides clear synchronization references that simplify detection and measurement tasks
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 effectively reduces the power level of reflected waves, enhancing the efficiency and safety of plasma processing operations.
Implementation Method 1
The radio-frequency power supply is electrically coupled to a radio-frequency electrode to generate source radio-frequency power to generate plasma from a gas in the chamber
Implementation Method 2
The first sensor measures a power level of a reflected wave of the source radio-frequency power from a load
Implementation Method 3
The second sensor measures a voltage and a current on a feed line coupling the radio-frequency power supply and the radio-frequency electrode
Implementation Method 4
The bias power supply is electrically coupled to the substrate support to generate electrical bias energy. The electrical bias energy has a bias frequency and is cyclically generated in bias cycles each having a duration being an inverse of the bias frequency
Data Source
AI summary
In a plasma processing apparatus, electrical bias energy is provided from a bias power supply to a substrate support. Source radio-frequency power is provided from a radio-frequency power supply to a radio-frequency electrode through a feed line. A phase period having a minimum value of a power level of a reflected wave of the source radio-frequency power is identified from a plurality of phase periods in a bias cycle of the electrical bias energy. A reference value being a phase difference between a voltage and a current on the feed line in the identified phase period is determined. A source frequency of the source radio-frequency power is controlled for each phase period based on a result of comparison between the reference value and the phase difference between the voltage and the current on the feed line in a corresponding phase period of the plurality of phase periods.