Abstract
N-incorporated Ru films were deposited by atomic layer deposition (ALD) at a deposition temperature of 270°C using 1-isopropyl-4-methylbenzene-cyclohexa-1,3-dienyl ruthenium and N2/H2 mixture plasma as the precursor and reactant, respectively. The N content in the ALD-Ru films was controlled by changing the gas ratio [N2 versus the total gas (N2+H2) flow rates] in the reactant from 0.82 to 1. Secondary ion mass spectrometry depth profiling revealed an increase in N content in the film with increasing gas ratio. The amount of N in the ALD-Ru films had a considerable effect on the film properties, such as resistivity, crystallinity and microstructure. Although the resistivity of the pure ALD-Ru film was ~19μΩcm, the N-incorporated ALD-Ru films deposited with a gas ratio of 0.86 (N/Ru: ~0.38) showed a resistivity of ~340μΩcm, which increased continuously with increasing gas ratio. X-ray and electron diffraction revealed degradation in film crystallinity and decrease in grain size with increasing N incorporation into ALD-Ru films. Transmission electron microscopy showed that N-incorporated ALD-Ru films formed nanocrystalline and non-columnar grain structures. This is in contrast to that observed in the pure ALD-Ru film, which had a polycrystalline columnar grain structure. The growth rate of a representative N-incorporated Ru film deposited with a gas ratio of 0.86 showed a linear dependency on the number of ALD cycles; growth rate of 0.051nm/cycle at short incubation cycles of ~3. The step coverage was approximately 98% over the trench structure (aspect ratio: 4.5) with a top opening width of 25nm. The direct plating of Cu on an optimized N-incorporated ALD-Ru film (5nm in thickness) was possible. The structure of Cu (80nm)/N-incorporated ALD-Ru (8nm)/Si was found to be stable without the formation of copper silicide after annealing at 600°C for 30min.
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