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

Abstract

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.