Atomic layer deposition of Y2O3 and yttrium-doped HfO2 using a newly synthesized Y(iPrCp)2(N-iPr-amd) precursor for a high permittivity gate dielectric

Abstract

We systematically investigated the effects of Y doping in HfO 2 dielectric layer, focusing on structural phase transformation and the dielectric properties of the resultant films. Y doping was carried out using atomic layer deposition (ALD) with a novel Y(iPrCp)2(N-iPr-amd) precursor, which exhibits good thermal stability without any decomposition and clean evaporation. As a result, the ALD process of the Y 2 O 3 films showed well-saturated and linear growth characteristics of ∼0.45 Å/cycle without significant incubation delays and produced pure Y 2 O 3 films. Then, yttrium-doped HfO 2 films with various Y/(Y + Hf) compositions (yttrium content: 0.6- 4.8 mol%) were prepared by alternating Y 2 O 3 and HfO 2 growth cycles. Structural and electrical characterization revealed that the addition of yttrium to HfO 2 induced phase transformations from the monoclinic to the cubic or tetragonal phases, even at low post-annealing temperatures of 600 C, and improved leakage current densities by inducing oxygen vacancy-related complex defects. A maximum relative dielectric constant of ∼33.4 was obtained for films with a yttrium content of ∼1.2 mol%. Excellent EOT scalability was observed down to ∼1 nm without dielectric constant degradation. © 2014 Elsevier B.V. All rights reserved.