Circuit Options
The Metal Contact and Terminal features both allow the Terminal type to be Circuit. In this case, there are 3 options available, Parallel RC circuit, L–network, and Reversed L–network.
Parallel RC Circuit
The circuit diagram for the most general parallel RC circuit is shown below:
The circuit includes an optional blocking capacitor (Cb) and stray capacitance (Cs). Both are off by default, and both make the model more nonlinear and thus more difficult to solve when active. The parallel RC circuit is often used to perform some initial investigations before moving onto designing a matching network.
l–Network
The L–network is a matching circuit designed to ensure maximum power transfer between the RF generator and the plasma. The most general form of the circuit is shown below:
As with the parallel RC circuit, the blocking capacitor and stray capacitance are optional, and off by default. The match inductance (Lm) and capacitance (Cp) can be adjusted to maximize the power transfer for a known plasma impedance. This type of match is only appropriate when the real part of the plasma impedance is below 50 Ω, which typically occurs when the discharge power is high.
Reversed L–Network
The reversed L-network is similar to the L-network, except the parallel capacitor is moved to the other side of the inductor:
As with the parallel RC circuit, the blocking capacitor and stray capacitance are optional, and off by default. This type of match is only appropriate when the real part of the plasma impedance is above 50 Ω, which typically occurs when the discharge power is low.
Enter the following settings:
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Source type. This determines whether the generator acts like a Voltage source (the default) or Power source. When Voltage source is selected:
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Enter the Voltage amplitude Vcir (SI unit: V) of the generator.
When Power source is selected:
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Enter the Source power Ps (SI unit: W) of the generator.
Using the Power source option is usually more stable, meaning that its more likely that the solver will converge than the Voltage source option.
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Enter the Series resistance Rs (SI unit: Ω) of the generator. This corresponds to the impedance the generator and is 50 Ω (the default value) in most practical applications.
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Enter the Parallel capacitance Cp (SI unit: F) which corresponds to the capacitance parallel to the plasma. When the Circuit type is L–network or Reversed L–network, this value can be computed to ensure proper matching.
Computing the Plasma Impedance: Application Library path Plasma_Module/Capacitively_Coupled_Plasmas/computing_plasma_impedance
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When the Circuit type is L–network or Reversed L–network, enter the Series inductance (SI unit: H). This value can also be computed to obtain a proper match.
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Enter the Source frequency fp (SI unit: Hz) of the generator. This value must be consistent with the value given for the Period property of the physics interface. See Using Consistent Source Frequencies and Period Settings for further information.
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Enter the Source phase α (dimensionless) of the generator. The default is zero and this rarely needs to be changed.
In the Additional Circuit Elements section, there are the following options:
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Include blocking capacitor. When this is active, enter the Blocking capacitance Cb (SI unit: F). This places a blocking capacitor between the plasma and the external circuit which will shield any accumulated surface charges on the electrode.
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Include stray capacitance. When this is active, enter the Stray capacitance Cs (SI unit: F). This adds an additional parallel capacitance across the plasma corresponding to stray leads or the vacuum capacitance of the system. The presence of a stray capacitance can lead to an impedance mismatch between the generator and plasma in a system which would otherwise be perfectly matched.