Multi-electrode source assembly for plasma processing

A plasma processing chamber, comprising:

• a substrate support assembly that comprises a substrate supporting surface that at least partially defines a processing region of the plasma processing chamber;
• a first electrode having a lower surface that is positioned over at least a portion of the substrate supporting surface, is substantially parallel to a first plane, and is a first distance from the substrate supporting surface in a first direction that is perpendicular to the first plane;
• a second electrode having a lower surface that is substantially parallel to the first plane, wherein the second electrode and the first electrode are spaced a distance apart in a second direction that is parallel to the first plane;
• a radio frequency (RF) power source assembly comprising:
• a first RF generator configured to provide an RF signal at a first RF frequency,
• an impedance matching network having an input coupled to an output of the first RF generator and an output coupled to the first electrode, and
• a tuning circuit having an input coupled to the output of the impedance matching network and an output coupled to the second electrode, wherein the tuning circuit comprises an LC circuit that has a resonant frequency at the first RF frequency, and comprises a first variable capacitor and a first inductor;
• and
• a controller configured to control the impedance of the first variable capacitor to cause an RF voltage and/or phase difference between a first RF waveform provided to the first electrode and the first RF waveform provided to the second electrode through the tuning circuit.

A plasma processing method, comprising:

• (a) generating a plasma in a processing region defined between an electrode assembly and a substrate supporting surface of a substrate support assembly, wherein the electrode assembly comprises a first electrode and a second electrode, the second electrode is positioned a distance from the first electrode in a first direction, a first radio frequency (RF) generator having an RF output, through an impedance matching network, that is coupled to the first electrode, and a tuning circuit coupled between the impedance matching network and the second electrode, wherein the tuning circuit comprises a plurality of impedance producing elements that comprise a first variable impedance producing element;
• (b) generating, by the first RF generator, an RF waveform, wherein the generated RF waveform establishes a first RF waveform at the first electrode and a second RF waveform at the second electrode;
• and
• (c) altering the generated plasma by adjusting the first variable impedance producing element of the tuning circuit, wherein adjusting the first variable impedance producing element alters one or more characteristics of the second RF waveform relative to the first RF waveform.