Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications

Abstract

Lanthanum aluminum oxide thin films were grown by atomic layer deposition from a lanthanum precursor, $\mathrm{tris}{\mathrm{(N,N}}^{\prime }$ -diisopropylacetamidinato)lanthanum $(\mathrm{La}{(}^{\mathrm{i}}\mathrm{PrAMD}{)}_3\mathrm{),}$ trimethylaluminum and water. Smooth, amorphous films having compositions ${\mathrm{La}}_{\text{0.5}}{\mathrm{Al}}_{\text{1.5}}{\mathrm{O}}_3$ and ${\mathrm{La}}_{\text{0.9}}{\mathrm{Al}}_{\text{1.1}}{\mathrm{O}}_3$ were deposited on HF-last silicon and characterized without postdeposition annealing. The films contained less than 1 at. % of carbon according to Rutherford backstattering spectrometry and secondary ion mass spectrometry. A thin (9.8 nm) film showed low leakage current ${\text{(<5}}^{*}{10}^{\text{−8}}\hspace{0.17em}{\mathrm{A/cm}}^2$ at 1 V for an equivalent oxide thickness of 2.9 nm), flatband voltage of $\text{−0.1\hspace{0.17em}}\mathrm{V}$ and low hysteresis (20 mV). Thicker films had even lower leakage currents ${\text{(<10}}^{\text{−8}}\hspace{0.17em}{\mathrm{A/cm}}^2$ at 2 MV/cm) but larger flatband shifts and more hysteresis. The permittivity of the films was 13 and the dielectric strength 4 MV/cm. Cross sectional high-resolution transmission electron microscopy showed a sharp interface between the film and the silicon substrate.