Electrical characterization of rare earth oxides grown by atomic layer deposition

In this contribution, we investigate the electrical properties of thin (3-30nm) Lu2O3 and Yb2O3 oxides grown on silicon by atomic layer depostion. Precursors with various ligands (e.g., cyclopentadienyls, or beta-diketonates) are used as metal source, while water or ozone are used as oxygen source. Lu2O3 and Yb2O3 films exhibit a dielectric constant (kappa) of 11 +/- 1 and 10 +/- 1, respectively. For both rare earth oxides, a low kappa interlayer (IL) is formed at the film/silicon interface. Gate stacks with capacitance equivalent oxide thickness (CET) down to 3 run exhibit low leakage current and well-shaped capacitance-voltage curves without frequency dispersion of the accumulation capacitance. A CET of 2.7 +/- 0.1 nm and leakage of 4.5 x 10(-4) A cm(-2) were measured for the thinnest (3.5nm) Lu2O3/IL/Si gate stack, and a CET of 3.3 +/- 0.1 nm and leakage of 1 x 10(-4) A cm(-2) for the (4-5 nm) Yb2O3/IL/Si one. The lowest interface trap density (D-it), measured for film grown using water, is in the 10(11) eV(-1) cm(-2) range for both rare earth oxides. Films grown using ozone exhibit a D-it in the 10(12) eV(-1) cm(-2) range. The microscopic structure of the electrically active defects is investigated using magnetic resonance spectroscopy.