Plasma-assisted atomic layer deposition of TiN films at low deposition temperature for high-aspect ratio applications

摘要

A plasma-assisted atomic layer deposition (PA-ALD) process of titanium nitride (TiN) using TiCl_4 precursor dosing and H_2/N_2 plasma exposure is presented. In situ spectroscopic ellipsometry revealed a growth rate at 400℃ 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℃ a relatively low chlorine impurity level (～2 at.%) arid low resistivity (～200 μΩ·cm) were obtained for a ～45 nm thick film. The growth rate was found to be considerably lower (～0.3 A/cycle) at this temperature. Using TEM imaging we found that PA-ALD TiN films can be deposited conformally in 20:1 aspect-ratio features (1.5 μm width) but that the step coverage still needs to be improved, probably by a prolonged plasma exposure step.