Low-Temperature Deposition of TiN by Plasma-Assisted Atomic Layer Deposition

Abstract

Titanium nitride (TiN) films were deposited by a plasma-assisted atomic layer deposition (PA-ALD) process, based on TiCl4 precursor dosing and remote H2 - N2 plasma exposure, at temperatures ranging from 100 to 400°C. The plasma, the PA-ALD process, and the resulting TiN material properties were extensively investigated. The plasma was studied by optical emission spectroscopy and Langmuir probe, revealing an ion density of 109 cm-3 and an electron temperature of 3.5 eV just above the substrate. Under floating conditions there is thus a considerable ion flux towards the substrate per ALD cycle with a typical ion energy of ∼15 eV. TiN film growth was studied by in situ spectroscopic ellipsometry, revealing self-limiting surface reactions for the complete temperature range. At 100°C the growth rate of 0.3 Åcycle was found to be significantly lower than the growth rate of 0.6 Åcycle at 400°C. The stoichiometry of the films varied with the plasma exposure time, while the Cl content was mostly affected by the deposition temperature (2.1 atom % at 100°C to 0.07 atom % at 400°C). Resistivities as low as 71 μ cm were obtained at a temperature of 400°C, while at 100°C a fair resistivity of 209 μ cm was reached. These results show that PA-ALD with TiCl4 and H2 - N2 plasma is well suited for low-temperature deposition of high-quality TiN films. © 2006 The Electrochemical Society.