Atomic beam deposition of lanthanum- and yttrium-based oxide thin films for gate dielectrics

We report on the electrical and microstructural characteristics of La- and Y-based oxides grown on silicon substrates by ultrahigh vacuum atomic beam deposition, in order to examine their potential as alternate gate dielectri cs for Si complementary metal oxide semiconductor technology. We have exami ned the issues of polycrystallinity and interfacial silicon oxide formation in these films and their effect on the leakage currents and the ability to deposit films with low electrical thickness. We observe that polycrystalli nity in the films does not result in unacceptably high leakage currents. We show significant Si penetration in both types of films. We find that the i nterfacial SiO2 is much thicker at similar to 1.5 nm for the Y-based oxide compared to the La-based oxide where the thickness is < 0.5 nm. We also sho w that while the Y-based oxide films show excellent electrical properties, the La based films exhibit a large flat band voltage shift indicative of po sitive charge in the films. (C) 2000 American Institute of Physics. [S0003- 6951(00)05143-3].