Atomic Layer Deposition of Nickel Carbide from a Nickel Amidinate Precursor and Hydrogen Plasma

Abstract

A new atomic layer deposition (ALD) process for depositing nickel carbide (Ni₃C _x) thin films is reported, using bis( N, N'-di- tert-butylacetamidinato)nickel(II) and H₂ plasma. The process shows a good layer-by-layer film growth behavior with a saturated film growth rate of 0.039 nm/cycle for a fairly wide process temperature window from 75 to 250 °C. Comprehensive material characterizations are performed on the Ni₃C _x films deposited at 95 °C with various H₂ plasma pulse lengths from 5 to 12 s, and no appreciable difference is found with the change of the plasma pulse length. The deposited Ni₃C _x films are fairly pure, smooth, and conductive, and the x in the nominal formula of Ni₃C _x is approximately 0.7. The ALD Ni₃C _x films are polycrystalline with a rhombohedral Ni₃C crystal structure, and the films are free of nanocrystalline graphite or amorphous carbon. Last, we demonstrate that, by using this ALD process, highly uniform Ni₃C _x films can be conformally deposited into deep narrow trenches with an aspect ratio as high as 20:1, which thereby highlights the broad and promising applicability of this process for conformal Ni₃C _x film coatings on complex high-aspect-ratio 3D architectures in general.