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

Ta36Si14N50 amorphous layers were reactive ion etched in CF4+O2 plasmas, The etch depth was determined as a function of gas composition, pressure, and cathode power. Adding small amounts of O2 to CF4 increased the etch rates up to approximately 15% O2 concentration, with etch rates then decreasing with further addition of O2. Etch rates increased with both pressure and power. Etching proceeded only after an initial delay 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 from Auger electron spectroscopy intensity depth profile measurements and is estimated to be 2 nm thick. Under optimal conditions, the etch rate of Ta36Si14N50 is about seven times higher than for SiO2, thus providing a high degree of selectivity for integrated circuit processing.