Examination and evaluation of La2O3 as gate dielectric for sub-100 nm CMOS and DRAM technology

High-k gate dielectric La₂O₃ thin films have been deposited on Si(1 0 0) substrates by molecular beam epitaxy (MBE). Al/La₂O₃/Si metal-oxide–semiconductor capacitor structures were fabricated and measured. A leakage current of 3 × 10⁻⁹ A/cm² and dielectric constant between 20 and 25 has been measured for samples having an equivalent oxide thickness (EOT) 2.2 nm. The estimated interface state density D_it is around 1 × 10¹¹ eV⁻¹ cm⁻². EOT and flat-band voltage were calculated using the NCSU CVC program. The chemical composition of the La₂O₃ films was measured using X-ray photoelectron spectrometry and Rutherford backscattering. Current density vs. voltage curves show that the La₂O₃ films have a leakage current several orders of magnitude lower than SiO₂ at the same EOT. Thin La₂O₃ layers survive anneals of up to 900 °C for 30 s with no degradation in electrical properties.