Ionized physical vapor deposition of titanium nitride: Plasma and film characterization

Abstract

The ionized physical vapor deposition of titanium nitride is experimentally investigated in terms of both plasma characteristics and TiN material properties. The vibrational and translational gas temperatures of N2 molecules are determined using optical emission spectroscopy by fitting the intensities of vibrational transitions to the nonequilibrium Treanor distribution. The gas temperature is typically 720 K at 15 mTorr. The dissociation of nitrogen is determined using mass spectrometry and found to increase with plasma power from 10% to 30% as the power is increased from 750 to 1500 W. From this data, it is calculated that the density of atomic nitrogen in the inductively coupled plasma source is the order of 1012 cm−3. Langmuir probe measurements indicate that the electron temperature is 1.6–2.0 eV and the ion density is (2–6)×1011 cm−3. Rutherford backscattering spectroscopy (RBS) shows that the TiNx films have increasing nitrogen composition (0.26<x<1.5) as the nitrogen content increases from 2% to 9% in the Ar/N2 plasma. The flux of nitrogen atoms from the plasma, as determined from the measured gas temperature and dissociation, is compared with the flux of nitrogen that is incorporated in the film according to RBS. The ratio of these two fluxes gives an upper-bound for the sticking coefficient of atomic N on TiNx, which is ∼0.1 for titanium-rich films and ∼0.003 for nitrogen-rich films.