Rf impedance matching network

A method of matching an impedance, the method comprising:

• coupling an impedance matching circuit between an RF source and a plasma chamber, the impedance matching circuit comprising:
• an RF input configured to operably couple to the RF source, the RF source providing an RF signal;
• an RF output configured to operably couple to the plasma chamber;
• a series electronically variable capacitor (EVC) electrically coupled in series between the RF input and the RF output;
• wherein the series EVC has a series variable capacitance;
• and
• wherein the series EVC comprises first fixed capacitors, each of the first fixed capacitors having a corresponding switch for switching in and out the fixed capacitor to alter the series variable capacitance, each switch comprising one or more diodes;
• and
• a first inductor having a first terminal electrically coupled to the common ground and a second terminal electrically coupled between the RF input and the RF output;
• determining a first parameter related to the plasma chamber while the RF source is providing the RF signal to the RF input;
• and
• while the RF signal continues to be provided to the RF input, altering the series variable capacitance based on the determined first parameter, wherein the alteration of the series variable capacitance causes RF power reflected back to the RF source to decrease.

A semiconductor processing tool comprising:

• a plasma chamber configured to deposit a material onto a substrate or etch a material from the substrate;
• and
• an impedance matching circuit operably coupled to the plasma chamber, the matching circuit comprising:
• an RF input configured to operably couple to an RF source providing an RF signal;
• an RF output configured to operably couple to the plasma chamber;
• a series electronically variable capacitor (EVC) electrically coupled in series between the RF input and the RF output;
• wherein the series EVC has a series variable capacitance;
• and
• wherein the series EVC comprises first fixed capacitors, each of the first fixed capacitors having a corresponding switch for switching in and out the fixed capacitor to alter the series variable capacitance, each switch comprising one or more diodes;
• a first inductor having a first terminal electrically coupled to the common ground and a second terminal electrically coupled between the RF input and the RF output;
• and
• a control circuit operably coupled to the series EVC, the control circuit configured to:
• determine a first parameter related to the plasma chamber while the RF source is providing the RF signal to the RF input;
• and
• while the RF signal continues to be provided to the RF input, alter the series variable capacitance based on the determined first parameter, wherein the alteration of the series variable capacitance causes RF power reflected back to the RF source to decrease.