US Patent 10026594 RF impedance matching network

In one embodiment, an RF impedance matching network includes an RF input configured to operably couple to an RF source; an RF output configured to operably couple to a plasma chamber; a first electronically variable capacitor having a first variable capacitance; a second electronically variable capacitor having a second variable capacitance; and a control circuit operably coupled to the first and second electronically variable capacitors. The control circuit is configured to determine the variable impedance of the plasma chamber, determine a first capacitance value for the first variable capacitance and a second capacitance value for the second variable capacitance, and generate a control signal to alter the first and/or second variable capacitance. 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.