Thermal stability and electrical properties of titanium-aluminum oxide ultrathin films as high-k gate dielectric materials

摘要

As potential high-k gate dielectric material for metal-oxide-semiconductor field effect transistor, the TiO_2 incorporated Al_2O_3 [(TiO_2)_x(Al_2O_3)_(1-x) (TAO)] films have been prepared by pulsed laser deposition. The thermal stability and electrical properties of the TAO films annealed at different temperatures have been systematically investigated by x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and capacitance-voltage measurements. These results show that the TAO films keep amorphous state after annealed at 900 ℃, and the interfacial reaction between the TAO film and silicon substrate is closely related to the deposition and postannealing temperatures. The dielectric constant of the film is about 30. For a 5 nm TAO film after annealed at 400 ℃, the thickness between interfacial layer and the silicon substrate is only two atomic layers (about 0.6 nm) and a small equivalent oxide thickness (1.2 nm) is achieved. A possible explanation for interfacial interaction has been proposed. By virtue of the leakage behaviors, Schottky emission is considered as the leakage mechanism of the TAO films. The advantages and disadvantages of the high-k gate dielectric material for future metal-oxide-semiconductor transistors have been discussed, which are useful for future practical application.