Plasma-assisted Atomic Layer Deposition of TiN Films at low Deposition Temperature for High-aspect Ratio Applications

Abstract

AbstractA plasma-assisted atomic layer deposition (PA-ALD) process of titanium nitride (TiN) using TiCl4 precursor dosing and H2/N2 plasma exposure is presented. In situ spectroscopic ellipsometry revealed a growth rate at 400 °C of ∼0.7 A/cycle independent of precursor dosing. Varying the plasma exposure time changed the stoichiometry [N]/[Ti] of the films within the range ∼0.93-1.15. At 100 °C a relatively low chlorine impurity level (∼2 at. %) and low resistivity (∼200 νΔcm) were obtained for a ∼45 nm thick film. The growth rate was found to be considerably lower (∼0.3 Å/cycle) at this temperature. Using TEM imaging we found that PAALD TiN films can be deposited conformally in 20:1 aspect-ratio features (1.5 Êm width) but that the step coverage still needs to be improved, probably by a prolonged plasma exposure step.