The nucleation and growth of Pt atomic layer deposition (ALD) on Al 2 O 3 substrates was studied using (methylcyclopentadienyl)-trimethyl platinum (MeCpPtMe 3 ) and O 2 plasma as the reactants. The nucleation of Pt ALD was examined on Al 2 O 3 ALD substrates at 300 C using a variety of techniques including spectroscopic ellipsometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and scanning electron microscopy. These techniques revealed that Pt ALD does not nucleate and grow immediately on the Al 2 O 3 ALD substrates. There was negligible Pt ALD during the first 38 ALD cycles. The Pt ALD growth rate then increased substantially during the next 12 ALD cycles. Subsequently, the Pt ALD growth rate reached a steady state linear growth regime for >50 ALD cycles. These measurements suggest that the Pt ALD first forms a number of nanoclusters that grow slowly during the first 38 ALD cycles. These islands then merge during the next 12 cycles and yield a steady state Pt ALD growth rate of $0.05 nm/cycle for >50 ALD cycles. The Pt ALD film at the onset of the steady state linear growth regime was approximately 2-3 nm in thickness. However, the SEM images of these Pt ALD films appeared corrugated and wormlike. These films also had a density that was only 50-70% of bulk Pt. Film densities that were consistent with bulk Pt were not observed until after >100 ALD cycles when the Pt ALD films appeared much smoother and were 4-5 nm in thickness. The Pt ALD nucleation rate could be enhanced somewhat using different O 2 plasma parameters.
Continuous and ultrathin platinum (Pt) films were deposited on tungsten (W) adhesion layers using atomic layer deposition (ALD) techniques. Pt ALD films were deposited at 120 °C using MeCpPtMe3 and H2 plasma as the reactants. X-ray reflectivity studies observed the rapid nucleation of the Pt film. X-ray photoelectron results were consistent with layer-by-layer growth suggesting a continuous Pt film at thicknesses ≥1.5 nm. The high surface energy of the W ALD adhesion layer enables the growth of continuous and ultrathin films of lower surface energy metals and should facilitate the use of precious metals for a variety of applications.
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