RF Matching Circuit Using Relay Coil Rectification for Plasma Loads
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Solution Overview
Problem
Existing plasma processing apparatuses face challenges in efficiently matching the impedance of the load to the output impedance of the radio-frequency power supply, which affects plasma generation and processing efficiency.
Innovation Solution
A matching circuit is introduced that includes reactance elements, relays with relay switches and coils, diodes connected in parallel to the relay coils to rectify radio-frequency currents, and capacitors connected in parallel to generate a direct-current voltage for the relay coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a matching circuit with relays and switching elements is used to adjust variable capacitance, then impedance matching capability is improved, but device complexity increases due to multiple relays and control circuits
Solution Approach 1:
The matching circuit automatically generates the required DC voltage for relay coils using the existing RF power signal through rectification and voltage doubling. The circuit serves itself by utilizing its own operating signal to power the control elements, eliminating the need for external DC power supplies and reducing overall system complexity.
Solution Approach 2:
The RF signal performs multiple functions: it provides plasma generation power, serves as the input signal for impedance matching, and simultaneously acts as the source for generating DC control voltage for the relay switches. This multi-functionality reduces the number of separate components needed in the system.
2Adaptability or versatility
If multiple relays and switching elements are employed to adjust capacitance, then impedance matching range is improved, but loss of energy increases due to multiple switching operations
Solution Approach 1:
The voltage doubling circuit continuously generates DC voltage from the RF signal during plasma processing operations. This continuous voltage generation ensures that relay switches can be actuated without interruption, maintaining continuous impedance matching adjustment capability throughout the plasma processing cycle.
3Device complexity
If parasitic capacitance between relay coil and reactance element is present, then device simplicity is improved, but harmful factors increase due to RF current interference
Solution Approach 1:
The parasitic capacitance between the relay coil and reactance element, which would normally cause harmful RF current leakage and interference, is instead utilized as the source for generating the DC control voltage. The rectifier circuit converts this previously harmful RF current into useful DC power for actuating the relay switches, transforming a disadvantage into an advantage.
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 solution effectively adjusts the variable capacitance of the matching circuit, improving impedance matching and enhancing plasma generation and processing efficiency.
Implementation Method 1
at least one diode connected in parallel to the relay coil of each of the plurality of relays and configured to rectify a radio-frequency current flowing through a parasitic capacitance between the relay coil and the corresponding reactance element
Implementation Method 2
at least one capacitor connected in parallel to the relay coil of each of the plurality of relays and configured to generate a direct-current (DC) voltage applied to the relay coil in response to a current generated by rectifying the radio-frequency current
Implementation Method 3
a radio-frequency current flowing through a parasitic capacitance between the relay coil and the corresponding reactance element
Data Source
AI summary
A matching circuit includes: a plurality of reactance elements connected to a supply line for supplying radio-frequency power for plasma generation; a plurality of relays, wherein each of the plurality of relays includes a relay switch having a first contact connected to a corresponding reactance element among the plurality of reactance elements and a second contact connected to a ground, and a relay coil; at least one diode connected in parallel to the relay coil of each of the relays and configured to rectify a radio-frequency current flowing through a parasitic capacitance between the relay coil and the corresponding reactance element; and at least one capacitor connected in parallel to the relay coil of each of the relays and configured to generate a direct-current (DC) voltage applied to the relay coil in response to a current generated by rectifying the radio-frequency current with the at least one diode.