Atomic Layer Deposition of Nickel by the Reduction of Preformed Nickel Oxide

A thin film of elementary nickel was formed by atomic layer deposition (ALD). The deposition cycle consisted of two consecutive chemical reaction steps: an oxidizing step and a reducing step. An atomic layer of nickel oxide was made by sequentially supplying bis(cyclopentadienyl)-nickel as a nickel precursor and water as an oxidation agent; the preformed atomic layer of nickel oxide was then reduced to elementary nickel metal by exposure to hydrogen radical at a deposition temperature of 165°C. Auger electron spectroscopy analysis detected negligible oxygen content in the grown films, indicating that the hydrogen radical had completely reduced the nickel oxide to a metallic thin film. In addition, carbon impurities in the film dropped from 16 atom % to less than 5 atom % during the reduction reaction. The proposed two-step ALD method for elementary metals was successful in forming continuous and conformal nickel thin films. These nickel films formed an effective glue layer between chemical vapor deposited copper and a diffusion barrier layer of TiN. The adhesion of a 1 μm thick copper film to a 15 nm thick nickel glue layer over a TiN barrier film was excellent, with no failures occurring during adhesive tape peel tests.