Examination and evaluation of La 2O 3 as gate dielectric for sub-100 nm CMOS and DRAM technology

Abstract

High- k gate dielectric La 2O 3 thin films have been deposited on Si(1 0 0) substrates by molecular beam epitaxy (MBE). Al/La 2O 3/Si metal-oxide–semiconductor capacitor structures were fabricated and measured. A leakage current of 3 × 10 −9 A/cm 2 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 × 10 11 e V −1 cm −2. EOT and flat-band voltage were calculated using the NCSU CVC program. The chemical composition of the La 2O 3 films was measured using X-ray photoelectron spectrometry and Rutherford backscattering. Current density vs. voltage curves show that the La 2O 3 films have a leakage current several orders of magnitude lower than SiO 2 at the same EOT. Thin La 2O 3 layers survive anneals of up to 900 °C for 30 s with no degradation in electrical properties.