REACTIVE ION ETCHING OF TA-SI-N DIFFUSION-BARRIERS IN CF4+O2

Ta36Si14N50 amorphous layers were reactive ion etched in CF4+O2 plasma s, The etch depth was determined as a function of gas composition, pre ssure, and cathode power. Adding small amounts of O2 to CF4 increased the etch rates up to approximately 15% O2 concentration, with etch rat es then decreasing with further addition of O2. Etch rates increased w ith both pressure and power. Etching proceeded only after an initial d elay time which depended upon gas composition and power. The delay is probably caused by a surface native oxide which must be removed before etching can commence. The presence of a surface oxide was observed fr om Auger electron spectroscopy intensity depth profile measurements an d is estimated to be 2 nm thick. Under optimal conditions, the etch ra te of Ta36Si14N50 is about seven times higher than for SiO2, thus prov iding a high degree of selectivity for integrated circuit processing.