Electronic Knob for Tuning Radial Etch Non-Uniformity at VHF Frequencies

A method for processing a wafer in a chamber with an electrode having a support surface and an outer edge region defined thereon, the chamber defined for plasma processing of the wafer, the method comprising:

• determining a radio frequency (RF) power to be applied to the electrode of the chamber via a conductive delivery connection, the conductive delivery connection having a first end, a second end and an associated dimension;
• determining capacitance to be set at the first end based on the RF power, so as to cause an impedance adjustment at the first end and an opposite impedance adjustment at the second end at an operating frequency of the RF power;
• and
• tuning a variable capacitor disposed between a RF power source and the first end of the conductive delivery connection to the determined capacitance , the capacitance causing the opposite impedance adjustment at the second end of the conductive delivery connection, the opposite impedance adjustment from the second end presented to the outer edge region of the electrode through a dielectric surround structure that surrounds the electrode, such that increasing the capacitance at the first end causes a decrease of impedance at the first end and an increase of impedance at the second end and a corresponding increase in a voltage distribution near the outer edge region of the electrode that decreases toward a center of the support surface of the electrode,
• wherein the dielectric surround structure surrounding the electrode is coupled to the second end.