RF impedance matching network

A method for radio frequency (RF) impedance matching, the method comprising:

• coupling an RF impedance matching circuit between an RF source having a fixed impedance and a plasma chamber, the matching circuit comprising:
• a first electronically variable capacitor (EVC) coupled to an RF input of the matching circuit to receive an RF signal from an RF source at a first frequency;
• and
• a second EVC separate and distinct from the first EVC, the second EVC coupled to the RF input to receive the RF signal from the RF source at the first frequency, wherein the first EVC has two terminals, the second EVC has two terminals, and the two terminals of the first EVC are not both common to the two terminals of the second EVC;
• receiving, at the RF input of the matching circuit, the RF signal at the first frequency from the RF source;
• determining a first parameter related to the plasma chamber, the matching circuit, or the RF source;
• determining, based on the first parameter, both:
• a first capacitance value or configuration (CVOC) for the first EVC;
• and
• a second CVOC for the second EVC;
• and
• generating one or more control signals to alter the first EVC to the first CVOC and the second EVC to the second CVOC;
• wherein the alteration of the first EVC and the second EVC 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 and to receive an RF signal at a frequency from the RF source, the RF source having a fixed output impedance;
• an RF output configured to operably couple to the plasma chamber;
• a first electronically variable capacitor (EVC) coupled to the RF input to receiver the RF signal from the RF source at the first frequency;
• a second EVC separate and distinct from the first EVC, wherein the first EVC, the second EVC coupled to the RF input to receive the RF signal from the RF source at the first frequency has two terminals, the second EVC has two terminals, and the two terminals of the first EVC are not both common to the two terminals of the second EVC;
• and
• a control circuit operably coupled to the first and second EVCs and configured to:
• determine a first parameter related to the plasma chamber, the matching circuit, or the RF source;
• determine, based on the first parameter, both (a) a first capacitance value or configuration (CVOC) for the first EVC, and (b) a second CVOC for the second EVC;
• and
• generate one or more control signals to alter the first EVC to the first CVOC and the second EVC to the second CVOC;
• wherein the alteration of the first EVC and the second EVC causes RF power reflected back to the RF source to decrease.