XPS studies of the ALD-growth of TaN diffusion barriers: Impact of the dielectric surface chemistry on the growth mechanism

Abstract

The introduction of SiOCH low- k dielectrics in the copper interconnections of sub-45 nm node technologies is a challenge in terms of both material and process criteria. For instance, the deposition of a diffusion barrier between copper and dielectric is strongly dependent on the nature of the dielectric surface. In this study, we investigate the first steps of ALD TaN growth with respect to dielectric surface chemistry, using XPS measurements. Three different dielectrics have been tested: SiOCH, SiO 2 or SiOCH capped by a thin SiO 2 layer. We show that TaN can only grow over a monolayer-thick Ta 2O 5 formed at the early stages of deposition. A mechanism for the growth first steps is described, explaining the incubation delays observed for the appearing of Ta–O and Ta–N bonds. In addition, we show that a 3 nm-thick SiO 2 layer is able to hide the effect of SiOCH chemistry and obtain similar growth rates on SiOCH and SiO 2.