Moveable edge rings with reduced capacitance variation for substrate processing systems
An edge ring for a plasma processing system includes a first annular body configured to surround a substrate support during plasma processing, an upper surface, a lower surface, a radially inner surface, a radially outer surface, and N spacers arranged in N spaced locations on the radially outer surface of the edge ring to reduce variations in a predetermined gap between the first annular body of the edge ring and a structure separate from the edge ring as the edge ring is heated and cooled during plasma processing.
1 . A lower edge ring for a plasma processing system, the lower edge ring comprising:
a first annular body configured to surround a substrate support during plasma processing;
an upper surface,
a lower surface;
a radially inner surface;
a radially outer surface, the upper surface and the radially outer surface configured to face an annular recess of a top edge ring; and
N spacers arranged in N spaced locations on the radially outer surface of the lower edge ring to reduce variations in a predetermined gap between the radially outer surface and the top edge ring, where N is an integer greater than or equal to 3 and less than or equal to 8,
wherein at least one of the N spacers includes a projection formed on the radially outer surface of the lower edge ring, and
wherein the projection includes a flat surface extending in a vertical direction along a vertical thickness of the radially outer surface.
2 . The lower edge ring of claim 1 , wherein the N spacers are arranged with a spacing of 360°/N.
3 . The lower edge ring of claim 1 , further comprising a coating covering the projection.
4 . The lower edge ring of claim 3 , wherein the coating includes an insulating material.
5 . The lower edge ring of claim 4 , wherein the coating is selected from a group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), aluminum oxide deposited using atomic layer deposition, yttrium oxide deposited using atomic layer deposition, and yttrium fluoride deposited using atomic layer deposition.
6 . The lower edge ring of claim 1 , wherein N=5.
7 . An edge ring system comprising the lower edge ring of claim 1 , the edge ring system further comprising:
the top edge ring, wherein the top edge ring includes an annular body configured to surround the substrate support during plasma processing.
8 . The edge ring system of claim 7 , further comprising a lift pin to lift the top edge ring relative to the lower edge ring to adjust a height of the upper surface of the top edge ring relative to a substrate on the substrate support.
9 . The lower edge ring of claim 1 , wherein the projection extends in a vertical direction fully along the vertical thickness of the radially outer surface of the lower edge ring.
10 . The lower edge ring of claim 1 , wherein a width of the projection is less than a distance between adjacent ones of the N spacers.
11 . The lower edge ring of claim 1 , wherein the flat surface of the projection extends partially along the vertical thickness of the radially outer surface.
12 . The lower edge ring of claim 1 , wherein the flat surface of the projection extends fully along the vertical thickness from a top edge of the radially outer surface to a bottom edge of the radially outer surface.
13 . The lower edge ring of claim 1 , wherein the projection is integral with the first annular body.
14 . The lower edge ring of claim 1 , wherein the projection extends in a range from 50 micrometers to 250 micrometers from the radially outer surface.
15 . The lower edge ring of claim 1 , wherein portions of the radially outer surface between adjacent ones of the N spacers are defined by machined or removed areas of the lower edge ring.