Investigation of Ta-RuO2 diffusion barrier for high density memory capacitor applications

초록

The properties of both oxygen indiffusion and oxidation resistance in a Ta+RuO<inf>2</inf> layer for high density memory devices were investigated by using Rutherford backscattering spectroscopy, four point probe, x-ray diffraction, x-ray photoelectron spectroscopy, and planar transmission electron microscopy. The Ta+RuO<inf>2</inf>/Si system sustained up to 800 °C without an increase in resistivity. The Ta+RuO<inf>2</inf> diffusion barrier showed a Ta amorphous microstructure and an embedded RuO<inf>x</inf> nanocrystalline structure in the as-deposited state. The Ta+RuO<inf>2</inf> film showed the formation of RuO<inf>2</inf> phase by reaction with the indiffused oxygen from atmosphere after annealing in an air ambient. The Ta+RuO<inf>2</inf> diffusion barrier showed that Ta is sufficiently bound to oxygen in the as-deposited state, but RuO<inf>2</inf> consists of Ru and Ru-O binding state. The Ta-O bonds showed little change compared to the as-deposited state with increasing annealing temperature, whereas Ru-O bonds significantly increased and transformed to conductive oxide, RuO<inf>2</inf>. Therefore, the Ta layer deposited by RuO<inf>2</inf> addition effectively prevented the indiffusion of oxygen up to 800 °C and its oxidation resistance was superior to various barriers reported by others. © 1998 American Vacuum Society.