A previously developed metal-organic atomic layer deposition (ALD) tantalum
nitride (TaNx) process was employed to investigate the growth of
TaNx liners on low dielectric constant (low-k) materials for
liner applications in advanced Cu/low-k interconnect metallization schemes.
ALD of TaNx was performed at a substrate temperature of 250°C by
alternately exposing low-k materials to
tertbutylimido-tris(diethylamido)tantalum (TBTDET) and ammonia
(NH3), separated by argon purge steps. The dependence of
TaNx film thickness on the number of ALD cycles performed on
both organosilicate and organic polymer-based low-k materials was determined
and compared to baseline growth characteristics of ALD TaNx on
SiO2. In order to assess the effect of the deposition of
TaNx on surface roughness, atomic force microscopy (AFM)
measurements were carried out prior to and after the deposition of
TaNx on the low-k materials. The stability of the interface
between TaNx and the low-k materials after thermal annealing at
350°C for 30 minutes was studied by examining interfacial roughness profiles
using cross-sectional imaging in a high-resolution transmission electron
microscope (HR-TEM). The wetting and adhesion properties of Cu/low-k were
quantified using a solid-state wetting experimental methodology after
integration of ALD TaNx liners with Cu and low-k dielectrics.