BCL3/CL2 ETCHING OF TUNGSTEN SILICIDE.

Previous attempts with chlorine-based etches in batch, parallel plate, reactive ion etch (RIE) reactors have yielded less than desirable film profiles and step coverage over underlying poly films. Anomalies found after RIE in these reactors include nonvertical etch profiles and polysilicon-to-polysilicon shorts due to poor etch selectivity to underlying oxides. This article describes a process for etching tungsten silicide films by using a BCl//3 and Cl//2 chemistry in a hexode reactor, which yields excellent profile control an improved selectivity to thermal oxide.