Modulation of rf returning straps for uniformity control

An apparatus for processing a substrate, comprising:

• a chamber body defining a processing volume, wherein the chamber body has a slit valve opening configured to allow passages of substrates;
• a substrate support disposed in the processing volume, wherein the substrate support is configured to receive a substrate on a supporting surface and to support the substrate during processing;
• a gas distribution plate disposed in the processing volume and above the substrate support, wherein the gas distribution plate is configured to deliver one or more processing gas;
• a radio frequency power source connected with the gas distribution plate;
• and
• a plurality of RF returning straps connected between a periphery of the substrate support and the radio frequency power source, wherein the plurality of RF returning straps is disposed such that impedance between the substrate support and the radio frequency power source varies along the periphery of the substrate support.

An apparatus for processing a substrate, comprising:

• a chamber body defining a processing volume;
• a first electrode disposed in the processing volume;
• a second electrode disposed in the processing volume, wherein the second electrode is opposing the first electrode and the first and second electrodes form a plasma volume therebetween;
• a radio frequency power source coupled to the first electrode;
• and
• a plurality of RF returning straps coupled between the second electrode and a body at a predetermined electrical potential, wherein the plurality of RF returning straps are coupled to a periphery of the second electrode, and impedance of the plurality of RF returning straps varies along the periphery of the second electrode.