BOTTOM EDGE RINGS

A bottom ring is configured to support a moveable edge ring. The edge ring is configured to be raised and lowered relative to a substrate support. The bottom ring includes an upper surface, an annular inner diameter, an annular outer diameter, a lower surface, and a plurality of vertical guide channels provided through the bottom ring from the lower surface to the upper surface of the bottom ring. Each of the guide channels includes a first region having a smaller diameter than the guide channel, and the guide channels are configured to receive respective lift pins for raising and lowering the edge ring. Each of the guide channels has a cavity on the lower surface of the bottom ring, wherein the cavities have a diameter greater than the guide channel.