Characterization of Atomic Layer Deposited WN_xC_y Thin Film as a Diffusion Barrier for Copper Metallization

摘要

The film properties of WN_xC_y films deposited by atomic layer deposition (ALD) using WF_6, NH_3, and triethylboron source gases were characterized as diffusion barrier for Cu metallization. It is noted that the as-deposited film shows an extremely low resistivity of about 350 μΩ-cm with a film density of 15.37 g/cm~3. The film composition measured from Rutherford backscattering spectrometry shows W, C, and N of approximately 48, 32, and 20 at.%, respectively. Transmission electron microscopy analyses show that the as-deposited film is composed of face-centered-cubic phase with a lattice parameter similar to both β-WC_(1-x) and β-W_2N with an equiaxed microstructure. The barrier property of this ALD-WN_xC_y film at a nominal thickness of 12 nm deposited between Cu and Si fails only after annealing at 700℃ for 30 minutes while the sputter-deposited Ta (12 nm) and ALD-TiN (20 nm) fail at 650 and 600℃, respectively. It is thought that the superior diffusion barrier performance of ALD-WN_xC_y film is the consequence of both nanocrystalline equiaxed grain structure and the formation of high density film.