A controlled growth of WNx, and WCx thin films prepared by atomic layer deposition

Abstract

This work reports a capability for a controlled preparation of tungsten nitride and carbide thin films via an atomic layer deposition (ALD) approach. Those films were deposited by ALD using a fluorine- and nitrogen -free W metallorganic precursor of tungsten tris(3-hexyne) carbonyl [W(CO)(CH3CH2C CH2CH3)] and a N-2 + H-2 mixture plasma as a reactant at a deposition temperature of 250 degrees C. It was found that a phase, microstructure and composition of the films could be controlled in precision by varying a gas flow rate ratio of N-2/H-2 in the plasma reactant. With the N-2/H-2 gas ratio of 1:3 and 1:5, W -rich polycrystalline WNx thin films (W/N ratio: similar to 1.39) were deposited with a resistivity of 700-900 mu Omega cm, while nano -crystalline (close to an amorphous) W -rich WCx films (W/C ratio: similar to 1.26) with a much lower resistivity of similar to 510 mu Omega cm, without any nitrogen incorporation, were formed when H-2 gas became extremely rich (N-2/H-2 gas ratio of 1:10). Both X-ray diffraction and electron diffraction analyses revealed that the ALD-WCx films were composed of hexagonal W2C, WC, and non-stoichiometric cubic beta-WCx. while the ALD-WNx films of cubic W2N. (C) 2016 Elsevier B.V. All rights reserved.