A comparative study of thermal and plasma enhanced ALD Ta-N-C films on SiO2, SiCOH and Cu substrates

Thermal and plasma enhanced atomic layer deposition (ALD) of tantalum nitride (TaN) thin films have been performed using PDMAT and NH₃, and TBTDET in combination with hydrogen radicals and argon ions, respectively. The films were grown on SiO₂, SiCOH and Cu, to study the influence of diverse kinds of substrates on growth behaviour and properties of ultra thin TaN layers. X-ray reflectometry (XRR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize these films. Their step coverage in 65 nm technology test structures and Cu diffusion into bare Si- wafers were also investigated. In the case of thermal ALD resulting non-metallic Ta-N-C films show good growth behaviour on SiO₂ and Cu, but some difficulties were revealed on SiCOH. Contrary, the use of plasma led to Ta-C-N films on all three substrates. They are rather tantalum carbide in nature and possess resistivities of less than 300 muOmegacm. A 1 nm PEALD barrier proved to be stable against Cu diffusion during a 30 min anneal at 400degC.