Growth and characterization of Hf–aluminate high-k gate dielectric ultrathin films with equivalent oxide thickness less than 10 Å

Abstract

Ultrathin amorphous Hf–aluminate (Hf–Al–O) films have been deposited on p-type (100) Si substrates by pulsed-laser deposition using a composite target containing HfO2 and Al2O3 plates. Transmission electron microscopy observation of Hf–Al–O films showed that the amorphous structure of Hf–Al–O films was stable under rapid thermal annealing at temperatures up to at least 1000 °C. Capacitance–voltage measurement of a 38 Å Hf–Al–O film revealed that the relative permittivity of the film was about 16. Such a film showed very low leakage current density of 4.6×10−3 A/cm2 at 1 V gate bias. The Hf–Al–O film under optimized condition did not show any significant interfacial layer at the interface and an equivalent oxide thickness of less than 10 Å has been achieved. The formation of Hf–O and Al–O bonds in the film was revealed by x-ray photoelectron spectroscopy.