Structure and dielectric properties of amorphous LaAlO3 and LaAlOxNy films as alternative gate dielectric materials

Abstract

Amorphous LaAlO3 (LAO) and LAOxNy (LAON) films have been prepared by pulsed laser deposition technique on Si (100) substrates and Pt coated silicon substrates. X-ray diffraction, transmission electron microscopy and differential thermal analysis investigations showed that both kinds of films remain amorphous up to a high temperature of 860 °C. Atomic force microscopy study indicated that the surface of the deposited films is very smooth with a root mean square roughness of 0.14 nm for 8 nm LAO. LAON films have a smoother surface than that of LAO films. High-resolution transmission electron microscope studies showed there often exists interfacial reaction between LAO and Si. One LAON/Si structure nearly without interfacial layer has been obtained. For LAO films, high bandgap of 6.55 eV and medium dielectric constant of 25–27 have been obtained. The LAON films showed small equivalent oxide thickness of 1.1 nm with a low leakage of 0.074 A/cm2@Vg=+1 V. It is proposed that amorphous LAON films are very promising dielectric materials for high k gate dielectric applications.