Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process
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Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process Chris Muratore1, John J. Moore1, J. Alan Rees2, Dan Carter3, Greg Roche3 Advanced Coatings and Surface Engineering Laboratory, Colorado School of Mines 1500 Illinois Street, Golden, CO 80401-1887, USA 2 Hiden Analytical Limited, 420 Europa Boulevard, Warrington, WA5 5UN England 3 Advanced Energy Industries, 1625 Sharp Point Drive, Fort Collins, CO 80525 USA 1
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 INTRODUCTION Many processing schemes that allow manipulation of the energy distributions of reactive species for reactive deposition processes are currently available and are used to increase deposition rate and manipulate film micro- or lattice structures. One such method is inductively coupled reactive plasma enhanced unbalanced magnetron sputtering [1], in which the reactive gas is excited by a plasma source independent of the unbalanced magnetron glow discharge. Several authors have shown or speculated on how reactive species distributions, and therefore film structures, can be modified by varying gas flow or power to the reactive plasma source [1,2,3]. This work shows that adding small amounts of reactive gas before excitation in a plasma source can also modify reactive ion energy distributions and resultant thin film microstructures. EXPERIMENTAL PROCEDURE a. Plasma characterization The Advanced Energy ICP source operates at 2 MHz nominally and uses a radio frequency power supply with a 3 kilowatt maximum output. The source was fitted with a removable Pyrex guide tube, designed to deliver the reactive plasma to the substrate. This source was characterized using a Hiden Analytical Limited (HAL) electrostatic quadrupole mass spectrometer/particle energy analyzer (EQP), which is
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