US Patent 7338578 Step edge insert ring for etch chamber

An insert ring for a wafer support inside a processing chamber for the processing, particularly dry etching, of semiconductor wafer substrates. The insert ring has a generally step-shaped cross-sectional configuration which defines a perpendicular gap or flow space between the insert ring and the wafer support. In the etching of substrates on the wafer support, the perpendicular gap or flow space defines a perpendicular flow path for plasma species. Consequently, flow of heavy plasma species against the outer wall of the wafer support is substantially hindered or reduced to reduce accumulation of polymer material on the inner surface of the insert ring and/or the outer wall of the wafer support.