Atomic layer deposition of copper nitride film and its application to copper seed layer for electrodeposition

We report the formation of smooth and conformal copper seed layer for electrodeposition by atomic layer deposition (ALD) and reducing anneal of a copper nitride film. The ALD copper nitride film was prepared at 100-140 C using bis(1-dimethylamino-2-methyl-2-butoxy)copper(II) and NH₃, and reduced to metallic copper film by annealing at 200 C or higher temperatures. The growth rate of ALD copper nitride was 0.1 nm/cycle at 120-140 C on both ruthenium and silicon oxide substrates, and the thickness of film was reduced approximately 20% by annealing. The resistivity of the 4.2 nm-thick copper film was 30 μω·cm. Both the ALD copper nitride and the reduced copper films exhibited extremely smooth surface and excellent step coverage, whereas the copper film deposited using alternating exposures to the copper precursor and H₂ showed a rough surface. The copper film electrodeposited on the copper seed of this study exhibited lower resistivity and smoother surface as compared to the copper film electrodeposited on the ALD ruthenium seed.