Reactive ion etching apparatus

Abstract

Disclosed is a RIE apparatus wherein the anode (maintained at ground potential) is composed of a three-plate configuration and is disposed in parallel relationship with the cathode plate. The top and middle plates of the anode have small gas pump-out holes and are affixed to the chamber walls below the pump-out port to form a high pressure baffle chamber. A gas ring interposed between the top and middle anode plates permits uniform diffusion of etchant species into the reaction volume. The third plate (plasma potential reduction plate -PPRP) of the anode is flexibly attached to the middle plate and contains a large number of large holes compared to those in the top and middle plates. The minimum size of the holes in the PPRP is twice the plasma dark space to permit the plasma formed in the reaction volume below the PPRP to be sustained thereabove, thereby increasing the ratio of the grounded area to the cathode area to which the plasma is exposed. Consequently, the DC potential is increased and the plasma potential decreased resulting in an enlargement of the wafer load window, elimination of black silicon formation, increasing uniformity of etching across the entire cathode surface and better etch selectivity.