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 off Si(100) substrates by molecular beam epitaxy (MBE). Al/La2O3/Si metal-oxide-semiconductor capacitor structures were fabricated and measured. A leakage current of 3 x 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 Dit is around 1 x 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.