Nitridation and reoxidation of high‐k metal oxide thin films using argon excimer sources

Abstract

AbstractWe report for the first time the nitridation and reoxidation of metal oxide films with the active nitrogen and oxygen species produced by argon excimer sources. Preliminary results on 9 nm Ta2O5 films using this method exhibited excellent electrical properties with the leakage current density being up to 3 orders of magnitude lower than the as‐deposited films. Breakdown fields were found to be greater than 13 MV/cm. Accumulation capacitance with the nitrided film increased by 25% compared with the as‐deposited film. Optical transmittance was as high as 99% in the visible region and more than 74% in the UV region. The refractive index at 632.8 nm was high up to 2.2. The Ar excimer source emitted energetic VUV photons which could break nitrogen triple bonds to produce active nitrogen species and photodissociate O2 to form strong oxidant O3 and highly reactive O (1S) atoms, leading to the nitridation and reoxidation of Ta2O5 without the need for the use of H2O, NH3 and high temperature substrate heating. The nitridation process for a specific film thickness can be optimised by adjusting the VUV irradiation time to achieve increased accumulation capacitance and improved leakage property simultaneously. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)