Conductive TiN thin films grown by plasma-enhanced atomic layer deposition: Effects of N-sources and thermal treatments

Abstract

This work consists of optimizing TiN plasma-enhanced atomic layer deposition using two different N-sources: NH 3 and N 2. In addition to maximizing the growth per cycle (GPC) and to shorten the deposition duration, comprehensive in situ and ex situ physicochemical characterizations give valuable information about the influence of the N-source nature, their dilution in Ar, and the plasma power on layer’s final properties. N 2 and NH 3 dilutions within Ar are extensively investigated since they are critical to decreasing the mean free path ( ℓ) of plasma-activated species. A 1:1 gas ratio for the N-sources:Ar mixture associated with low flows (20 sccm) is optimal values for achieving highest GPCs (0.8 Å/cycle). Due to lower reactivity and shorter ℓ of the excited species, N 2 plasma is more sensitive to power and generator-to-sample distance, and this contributes to lower conformality than with NH 3 plasma. The resistivity of the initial amorphous films was high ( ≥ 1000 μ Ω  cm) and was significantly reduced after thermal treatment ( ≤ 400 μ Ω cm). This demonstrates clearly the beneficial effect of the crystallinity of the film conductivity. Though N 2 process appears slightly slower than the NH 3 one, it leads to an acceptable film quality. It should be considered since it is nonharmful, and the process could be further improved by using a reactor exhibiting optimized geometry.