Gadolinium silicate gate dielectric films with sub-1.5 nm equivalent oxide thickness

GdSi x O y gate dielectric films were deposited on Si(001) substrates using ultra-high-vacuum electron-beam evaporation from pressed-powder targets. Transmission electron microscopy showed that the films were amorphous as deposited and remained amorphous when annealed to temperatures up to 900 °C. Capacitance–voltage measurements indicate an equivalent oxide thickness (EOT) of 13.4 Å for a film with composition GdSi0.56O2.59 determined by in situ x-ray photoelectron emission spectroscopy. After forming gas annealing at 500 °C the EOT was reduced to 11.0 Å, at a physical thickness of 45 Å. The same film has a low leakage current of approximately 5.7×10−3 A cm−2 at +1 V, a reduction of 8.7×104 compared to current density estimates of SiO2 films with the same specific capacitance.