Characterization of Atomic Layer Deposited WN x C y Thin Film as a Diffusion Barrier for Copper Metallization

Abstract

The properties of films deposited by atomic layer deposition (ALD) using and triethyl boron were characterized as diffusion barriers for copper metallization. The films deposited at 313°C showed resistivity of about 350 μΩ cm with a density of The film composition measured by Rutherford backscattering spectrometry showed W, C, and N of approximately 48, 32, and 20 atom %, respectively. Transmission electron microscopy analyses showed that the as-deposited film was composed of a face-centered-cubic phase with a lattice parameter similar to both and with an equiaxed microstructure. The film kept its nanocrystalline microstructure until annealing at 700°C, although some amount of simple hexagonal α-WC was identified to be formed and the phase disappeared. As the annealing temperature increased to 800°C, relatively larger grains of body-centered-cubic W were newly formed with smaller grains of hexagonal-close-packed or α-WC. All the phenomena are related to nitrogen release after annealing at 700 and 800°C. The results of diffusion barrier performance between Cu and Si analyzed by X-ray diffractometry showed that film (12 nm) failed only after annealing at 700°C for 30 min by the formation of copper silicide, while the sputter-deposited Ta (12 nm) and ALD-TiN (20 nm) films failed at 650 and 600°C annealing, respectively. It is thought that the superior diffusion barrier performance of film is the consequence of both the formation of equiaxed microstructure and the high-density nature of the film. © 2004 The Electrochemical Society. All rights reserved.