Sensors and system for in-situ edge ring erosion monitor

A plasma processing chamber comprising:

• a chamber body having a plurality of walls defining an internal volume;
• a substrate support assembly disposed within the internal volume, wherein the substrate support assembly comprises:
• an outer periphery;
• and
• a substrate support extending to the outer periphery and having a top surface;
• an edge ring having an upper surface and a lower surface opposite the upper surface, the lower surface of the edge ring disposed on the top surface of the substrate support proximate the outer periphery;
• a sleeve configured to at least partially support the edge ring, the sleeve cylindrical in shape and circumscribing the substrate support, the sleeve having an opening formed along an upper surface of the sleeve, wherein the edge ring further comprises an attachment member aligned with the opening in the sleeve;
• and
• a first sensor fixedly disposed within the opening of the sleeve adjacent to and below the upper surface of the sleeve, the sleeve disposed below the top surface and outside the outer periphery of the substrate support assembly, the first sensor configured to detect a metric of erosion of the edge ring, wherein the first sensor is a displacement sensor, and the displacement sensor includes a flexible membrane attached to sidewalls of the opening and arranged such that the attachment member contacts and displaces the flexible membrane.