METAL-OXIDE-SEMICONDUCTOR CHARACTERISTICS OF CHEMICAL VAPOR-DEPOSITED TA2O5 FILMS

This letter describes the metal-oxide-semiconductor characteristics of chemical vapor deposited Ta2O5 films. With the passivation of bottom ultrathin SiO2 layer (approximately 3.4 nm), an excellent interface (i.e., low fixed charge and interface state densities) has been achieved. In this study, different top dielectrics such as SiO2 and Si3N4 were used to be compatible with conventional polycrystalline Si-gate process. By using top dielectrics deposited on Ta2O5, such as SiO2 and Si3N4, the leakage current is found to be greatly suppressed by three orders of magnitude for - V(g). For + V(g) the leakage current behaviors are believed to be governed by the Fowler-Nordheim tunneling through the bottom SiO2 layer. Under high-field stress, however, interface state generation was found to be enhanced with the presence of the top dielectric layer.