Reactive ion etching of Ta–Si–N diffusion barriers in CF_(4)+O_(2)

Abstract

Ta_(36)Si_(14)N_(50) amorphous layers were reactive ion etched in CF_(4)+O_(2) plasmas. The etch depth was determined as a function of gas composition, pressure, and cathode power. Adding small amounts of O_2 to CF_4 increased the etch rates up to approximately 15% O_2 concentration, with etch rates then decreasing with further addition of O_2. 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 Ta_(36)Si_(14)N_(50) is about seven times higher than for SiO_2, thus providing a high degree of selectivity for integrated circuit processing.

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