Achieving facile nucleation of noble metal films through atomic layer deposition (ALD) is extremely challenging. To this end, η4‐2,3‐dimethylbutadiene ruthenium(0)tricarbonyl (Ru(DMBD)(CO)3), a zero‐valent complex, has recently been reported to achieve good nucleation by ALD at relatively low temperatures and mild reaction conditions. The authors study the growth mechanism of this precursor by in situ quartz‐crystal microbalance and quadrupole mass spectrometry during Ru ALD, complemented by ex situ film characterization and kinetic modeling. These studies reveal that Ru(DMBD)(CO)3produces high‐quality Ru films with excellent nucleation properties. This results in smooth, coalesced films even at low film thicknesses, all important traits for device applications. However, Ru deposition follows a kinetically limited decarbonylation reaction scheme, akin to typical chemical vapor deposition processes, with a strong dependence on both temperature and reaction timescale. The non‐self‐limiting nature of the kinetically driven mechanism presents both challenges for ALD implementation and opportunities for process tuning. By surveying reports of similar precursors, it is suggested that the findings can be generalized to the broader class of zero‐oxidation state carbonyl‐based precursors used in thermal ALD, with insight into the design of effective saturation studies.
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Atomic layer deposition (ALD) of ruthenium (Ru) is being investigated for next generation interconnects and conducting liners for copper metallization. However, integration of ALD Ru with diffusion barrier refractory metal nitrides, such as tantalum nitride (TaN), continues to be a challenge due to its slow nucleation rates. Here, we demonstrate that an ultraviolet-ozone (UV-O3) pretreatment of TaN leads to an oxidized surface that favorably alters the deposition characteristics of ALD Ru from islandlike to layer-by-layer growth. The film morphology and properties are evaluated via spectroscopic ellipsometry, atomic force microscopy, electrical sheet resistance measurements, and thermoreflectance. We report a 1.83 nm continuous Ru film with a roughness of 0.19 nm and a sheet resistance of 10.8 KΩ/□. The interface chemistry between TaN and Ru is studied by x-ray photoelectron spectroscopy. It is shown that UV-O3 pretreatment, while oxidizing TaN, enhances Ru film nucleation and limits further oxidation of the underlying TaN during ALD. An oxygen “gettering” mechanism by TaN is proposed to explain reduced oxygen content in the Ru film and higher electrical conductivity compared to Ru deposited on native-TaN. This work provides a simple and effective approach using UV-O3 pretreatment for obtaining sub-2 nm, smooth, and conducting Ru films on TaN surfaces.
more » « less- PAR ID:
- 10531974
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Journal of Vacuum Science & Technology A
- Volume:
- 42
- Issue:
- 3
- ISSN:
- 0734-2101
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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