Investigation of high-quality ultra-thin LaAlO3 films as high-k gate dielectrics

Abstract

We have studied the formation of a high-quality LaAlO3 (LAO) film directly on silicon substrates by the pulsed laser deposition method as a novel high-k gate dielectric. The LAO films can remain amorphous at temperatures up to 850°C. An atomic force microscopy study indicated a very smooth surface of the deposited films with a rms of 0.14 nm for an 8 nm LAO film. The structures and electrical properties of metal–dielectric–semiconductor (Pt/LAO/Si) capacitors were investigated with LAO films deposited under different ambient conditions. High-resolution transmission electron microscopy indicated that interfacial reactions often occur for films of LAO deposited under oxygen ambient. A small effective oxide thickness of 1.2 nm was obtained for those films deposited under 20 Pa nitrogen ambient, with the corresponding leakage current density 17.1 mA cm−2 at +1 V gate voltage. It is proposed that amorphous LAO films are a novel promising alternative high-k gate dielectric material in future ultra-large scale integrated devices.