Electronically variable capacitor and RF matching network incorporating same

A method of matching an impedance, the method comprising:

• determining a variable impedance of a plasma chamber, with an impedance matching network electrically coupled between the plasma chamber and an RF source, wherein the RF source has a fixed impedance, and the impedance matching network includes a series electronically variable capacitor having a first variable capacitance and, coupled in series between the plasma chamber and the RF source, and a shunt electronically variable capacitor having a second variable capacitance and, coupled in parallel between a ground and one of the plasma chamber and the RF source;
• determining a first variable capacitance value and a second variable capacitance value for, respectively, the series electronically variable capacitor and the shunt electronically variable capacitor, for purposes of creating an impedance match at an RF input of the impedance matching network;
• and
• altering at least one of the first variable capacitance and the second variable capacitance to the first capacitance value and the second capacitance value, respectively, wherein an elapsed time between determining the variable impedance of the plasma chamber to when RF power reflected back to the RF source decreases is less than about 150 μsec.

A method of manufacturing a semiconductor comprising:

• placing a substrate in a plasma chamber configured to deposit a material layer onto the substrate or etch a material layer from the substrate;
• and energizing plasma within the plasma chamber by coupling RF power from an RF source into the plasma chamber to perform a deposition or etching, and while energizing the plasma:
• determining a variable impedance of the plasma within the plasma chamber, with an impedance matching network electrically coupled between the plasma chamber and the RF source, wherein the RF source has a fixed impedance, and the impedance matching network includes a series electronically variable capacitor having a first variable capacitance and coupled in series between the plasma chamber and the RF source, and a shunt electronically variable capacitor having a second variable capacitance and coupled in parallel between a ground and one of the plasma chamber and the RF source, determining a first variable capacitance value and a second variable capacitance value for, respectively, the series electronically variable capacitor and the shunt electronically variable capacitor, for purposes of creating an impedance match at an RF input of the impedance matching network;
• and altering at least one of the first variable capacitance and the second variable capacitance to the first capacitance value and the second capacitance value, respectively, wherein an elapsed time between determining the variable impedance of the plasma chamber to when RF power reflected back to the RF source decreases is less than about 150 μsec.