ULTRATHIN TA2O5 FILM GROWTH BY CHEMICAL-VAPOR-DEPOSITION OF TA(N(CH3)(2))(5) AND O-2 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 O-2 both bare and SiOxNy-passivated Si(100) using x-r ay photoelectron Spectroscopy, time-of-flight secondary-ion-mass spect roscopy (TOF-SIMS), and electrical measurements. The SiOxNy-passivated layer was formed by nitric oxide exposure to the Si substrate. Chemic al 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 O-2 flow rates. A co rresponding leakage current decrease is observed for the films grown a t a high O-2 flow rate. Compared to Ta2O5 films deposited on bare Si(1 00), the films deposited on SiOxNy-passivated layers show better elect rical properties; with smaller equivalent thickness (Delta t(eq) simil ar to 6 Angstrom) one order of magnitude lower leakage current was mea sured. TOF-SIMS data indicate that SiOxNy layers (similar to 9 Angstro m) incorporate some oxygen during Ta2O5 deposition; however, regions w here x=2, y=0 were not detected. Postdeposition annealing of Ta2O5/SiO xNy samples results in displacement of N by O in SiOxNy layers and oxi dation of the Si substrate, forming SiO2. (C) 1998 American Vacuum Soc iety.