Effects of aluminum doping on lanthanum oxide gate dielectric films

This work reports a novel method for improving the electrical properties of lanthanum gate oxide (La₂O₃) by using aluminum doping and rapid thermal annealing (RTA) techniques. In the bulk of the Al-doped La₂O₃ film together with 600 °C RTA, we found that the aluminum atoms were incorporated into the oxide network and the film was transformed into lanthanum aluminate complex oxide. At the interface, a thin Al₂O₃ layer was formed. This interfacial Al₂O₃ layer suppressed the out-diffusion of substrate Si, the formation of interfacial silicate layer and silicide bonds. These effects resulted in a significant reduction on the bulk and interface trap densities and hence the gate leakage current.