Moveable edge rings with reduced capacitance variation for substrate processing systems

Abstract

A moveable edge ring system for a plasma processing system includes a top edge ring and a first edge ring arranged below the top edge ring. A second edge ring is made of conductive material and includes an upper portion, a middle portion and a lower portion. The top edge ring and the second edge ring are configured to move in a vertical direction relative to a substrate support and the first edge ring when biased upwardly by a lift pin. The second edge ring is arranged below the top edge ring and radially outside of the first edge ring.

What is claimed is: 
     
         1 . An edge ring for a plasma processing system, comprising:
 an annular body;   a radially inner leg extending from the annular body;   a radially outer leg extending from the annular body,   wherein a first portion of an upper surface of the annular body is parallel to a plane including a substrate, and   wherein a second portion of the upper surface of the annular body slopes downward at an angle from the first portion.   
     
     
         2 . The edge ring of  claim 1 , wherein the first portion of the upper surface is located radially inward of the second portion of the upper surface. 
     
     
         3 . The edge ring of  claim 2 , wherein a third portion of the upper surface is parallel to the plane including the substrate and is located radially outward of the second portion of the upper surface. 
     
     
         4 . The edge ring of  claim 1 , wherein the edge ring has an inverted “U” shape. 
     
     
         5 . The edge ring of  claim 4 , wherein the second portion of the upper surface begins to slope downward at a horizontal distance h from a radially outer edge of the inverted “U” shape, and wherein the horizontal distance h is in a range from 0 mm to 10 mm. 
     
     
         6 . The edge ring of  claim 1 , wherein a thickness t of the annular body is in a range from 0.5 mm to 10 mm. 
     
     
         7 . The edge ring of  claim 6 , wherein the second portion of the upper surface slopes downward by a vertical distance of d that is greater than or equal to 20% of a height of an overall thickness of the edge ring. 
     
     
         8 . The edge ring of  claim 6 , wherein the second portion of the upper surface slopes downward by a vertical distance of d, and wherein d is greater than or equal to t. 
     
     
         9 . The edge ring of  claim 8 , wherein d is in a range from t to 3t. 
     
     
         10 . The edge ring of  claim 1 , wherein second portion of the upper surface slopes linearly at an acute angle.