High-Frequency Power Supply IMD Suppression via Frequency Modulation
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Solution Overview
Problem
In high-frequency power supply systems for plasma reactors, the rapid changes in plasma impedance due to the low-frequency bias power supply lead to increased inter-modulation distortion (IMD), resulting in higher reflected wave power, which hampers efficient power delivery to the load.
Innovation Solution
A high-frequency power supply system that includes a bias power supply, a source power supply, and a matching unit with an impedance matching circuit. The source power supply performs frequency modulation based on a delay setting value and the bias frequency to reduce IMD and suppress reflected wave power by aligning the frequency variation with the plasma impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual-frequency power supply is provided with a matching unit using an impedance-variable element operated by a motor, then impedance matching can be achieved between the power supply side and the plasma reactor device side, but the matching operation cannot follow the high-speed changes in plasma impedance caused by the low-frequency bias power supply, resulting in increased reflected wave power due to inter-modulation distortion
Solution Approach 1:
The patent replaces the motor-operated mechanical impedance adjustment system with an electronic impedance adjustment system. The electronic system uses solid-state components to achieve impedance matching, enabling response speeds that can follow the high-frequency variations in plasma impedance caused by the bias power supply, thereby reducing inter-modulation distortion and reflected wave power.
Solution Approach 2:
The patent implements a dynamic impedance adjustment mechanism that continuously adapts to changing plasma conditions. The electronic impedance adjustment system can rapidly modify impedance parameters in real-time to track the high-speed variations in plasma impedance, ensuring continuous optimal matching without the speed limitations of mechanical systems.
2Stability of the object's composition
If the impedance matching operation cannot follow the high-speed changes in plasma impedance, then the matching operation remains stable, but the amount of reflected wave power increases due to inter-modulation distortion
Solution Approach 1:
The patent implements a feedback control system that monitors the actual impedance conditions and adjusts the electronic impedance adjustment parameters accordingly. This closed-loop control ensures that the system maintains stable operation while dynamically adapting to plasma impedance changes, minimizing reflected wave power by continuously optimizing the impedance match based on real-time 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
The system effectively reduces IMD and reflected wave power, ensuring efficient and accurate power delivery to the load by synchronizing frequency variations with plasma impedance changes, thereby improving power supply reliability.
Implementation Method 1
the source power supply performs frequency modulation based on a delay setting value and the bias frequency to reduce IMD and suppress reflected wave power by aligning the frequency variation with the plasma impedance changes
Implementation Method 2
The matching unit superimposes the source power with the bias power and supplies the load with a superimposed power
Implementation Method 3
When a dual-frequency power supply is provided, as described in JP H07-74159 A, it is known that a plasma sheath is generated together with a plasma in a plasma chamber of the plasma reactor device
Data Source
AI summary
Techniques for suppressing an increase in reflected wave power (reflection coefficient) due to IMD are proposed. A high-frequency power supply system for providing a high-frequency power to a connected load includes: a bias power supply which outputs a bias power at a first frequency; a source power supply which outputs a source power at a second frequency higher than the first frequency; and a matching unit including an impedance matching circuit which acquires the bias power and the source power and matches an impedance of the source power supply side with an impedance of the load side. The source power supply determines a delay setting value indicating the timing of starting a frequency variation process with respect to the source power, performs the frequency variation process using the delay setting value and the value of the first frequency, and outputs a frequency-varied source power to the matching unit.