Ultrathin $Ta2O5$ film growth by chemical vapor deposition of $Ta(N(CH3)2)5$ and $O2$ on bare and $SiOxNy$-passivated Si(100) for gate dielectric applications

We investigated $Ta2O5$ films grown by chemical vapor deposition of $Ta(N(CH3)2)5$ and $O2$ both bare and $SiOxNy$-passivated Si(100) using x-ray photoelectron spectroscopy, time-of-flight secondary-ion-mass spectroscopy (TOF-SIMS), and electrical measurements. The $SiOxNy$-passivated layer was formed by nitric oxide exposure to the Si substrate. Chemical composition of the $Ta2O5$ films is strongly dependent on the oxygen flow rate during film deposition; lower carbon levels and higher O/Ta ratios are observed for the films grown at higher $O2$ flow rates. A corresponding leakage current decrease is observed for the films grown at a high $O2$ flow rate. Compared to $Ta2O5$ films deposited on bare Si(100), the films deposited on $SiOxNy$-passivated layers show better electrical properties; with smaller equivalent thickness $(Δteq∼6 Å),$ one order of magnitude lower leakage current was measured. TOF-SIMS data indicate that $SiOxNy$ layers $(∼9 Å)$ incorporate some oxygen during $Ta2O5$ deposition; however, regions where $x=2,$ $y=0$ were not detected. Postdeposition annealing of $Ta2O5/SiOxNy$ samples results in displacement of N by O in $SiOxNy$ layers and oxidation of the Si substrate, forming $SiO2.$