Edge ring assembly for improving feature profile tilting at extreme edge of wafer

A system for plasma processing, comprising:

• a process chamber;
• an electrostatic chuck (ESC) disposed in the process chamber, the ESC having a top surface that is configured to support a substrate during plasma processing, the ESC further including an annular step surrounding the top surface, the annular step defining an annular shelf at a lower height than the top surface;
• an upper edge ring disposed above the annular shelf, the upper edge ring being defined from an electrically insulating material;
• a lower inner edge ring disposed below the upper edge ring in the annular step and disposed on, and in contact with, the annular shelf, the lower inner edge ring having an electrically conductive structure defined from an electrically conductive material, the lower inner edge ring further having an anodization layer surrounding the electrically conductive structure so that the electrically conductive structure is electrically insulated from the ESC, the lower inner edge ring having a substantially rectangular cross-sectional shape, wherein a bottom surface of the lower inner edge ring directly contacts the annular shelf, and a side surface of the lower inner edge ring is adjacent to and surrounding a sidewall defined by the annular step;
• a lower outer edge ring surrounding the inner edge ring, the lower outer edge ring disposed below the upper edge ring in the annular step and disposed over the annular shelf, the lower outer edge ring being defined from an electrically insulating material;
• a bias electrode disposed within the ESC, the bias electrode configured to receive RF power from a first RF power supply to generate a bias voltage on the substrate.