Plasma diagnostics of triode ion-plating systems by energy-resolved mass spectroscopy and comparison of TiN film properties

Abstract

Plasma properties related to TiN deposition are compared in two triode ion-plating systems (System A and System B) using a low-voltage are discharge. System A employs a magnetic field, confining the are and the plasma, while System B does not. The systems also differ in the configuration of the chamber. TiN coatings are deposited in both systems over a range of negative bias voltages from 25 to 150 V. A correlation is established between the coating properties and the plasma parameters determined by energy-resolved mass spectrometry. The plasma potential in System B is between +15 and +35 V, featuring a spatial inhomogeneity. System A exhibits a higher plasma potential (about +55 V), resulting in higher energies of ions at substrates and a narrower energy distribution of ions. Unlike in System B, the population of Ti2+ in System A is even higher than that of Ti+. The presence of high-energy neutral Ti is observed. The texture coefficients and the stress-foe lattice parameters measured by X-ray diffraction on TiN films deposited at negative substrate bias in the range from 25 to 150 V behave similarly in both deposition systems but with a shift in bias necessary for similar properties. The appropriate bias in System B is about 75 V higher than in System A. This shift corresponds to the difference between the systems in the plasma potential and the degree of ionisation found by energy-resolved mass spectrometry. Other film properties, especially the film compressive stress, microhardness, critical load in scratch tests and the surface roughness, remain almost constant over the whole range of bias values in both systems. This means that these properties are less sensitive to ion bombardment in the triode ion-plating systems under the conditions studied. (C) 1999 Elsevier Science S.A. All rights reserved.