Ultrathin Ta₂O₅ film growth by chemical vapor deposition of Ta(N(CH₃)₂)₅ and O₂ on bare and SiO_xN_y-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 SiO_xN_y-passivated Si(100) using x-ray photoelectron spectroscopy, time-of-flight secondary-ion-mass spectroscopy (TOF-SIMS), and electrical measurements. The SiO_xN_y-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 SiO_xN_y-passivated layers show better electrical properties; with smaller equivalent thickness (Δt_eq∼6 Å), one order of magnitude lower leakage current was measured. TOF-SIMS data indicate that SiO_xN_y layers (∼9 Å) incorporate some oxygen during <- - roman>Ta₂O₅ deposition; however, regions where x=2, y=0 were not detected. Postdeposition annealing of Ta₂O₅/SiO_xN_y samples results in displacement of N by O in SiO_xN_y layers and oxidation of the Si substrate, forming SiO₂. © 1998 American Vacuum Society.