Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process

Abstract

Measurement of the ion energy distributions (IED's) of N₂⁺ ions produced in an inductively coupled plasma (ICP) source revealed that adding argon to the nitrogen gas before excitation in the source increased the nitrogen ion current. Adding helium resulted in an increase of the most probable ion energy, and a higher-energy component of the N₂⁺ IED at about 20 eV. Preliminary calculations of the electron energy distributions (EED's) correlate well to the IED's for both inert gas additions. Experiments were performed to determine the effect of these modified energy distributions of the reactive species on titanium nitride thin film growth rates, microstructure and mechanical properties. Deposition experiments were conducted using the ICP source and an unbalanced magnetron with a titanium cathode. Results showed that the argon inert gas addition resulted in increased deposition rate and reduced 3-D features. Film roughness was decreased to 1.61 nm from 2.05 nm when helium was mixed with the nitrogen. Mixing both argon and helium with the nitrogen yielded combined effects of deposition rate increase, reduced 3-D features and increased smoothness. The inert gas additions increased hardness of the TiN films from 17.3 GPa to 21.1 GPa with the argon addition and to 25.0 GPa with the helium addition