Structural and optical characterization of titanium nitride thin films deposited by magnetron sputtering

Abstract

Titanium nitride applicability covers different industries such as microelectronics, biomedicine and so on. This paper presents the analysis of the structural and optical properties of titanium nitride thin films for different deposition conditions. The samples were deposited by direct current magnetron sputtering on silicon substrates. The deposition was done at room temperature, on substrates preheated at 300 °C or on substrates that were polarized at -40 V and 90 V respectively. The results indicate a dependency of the structural orientation with respect to the deposition process when this takes place at room temperature. When the deposition was done on a preheated substrate there was no structural orientation. A negative polarization of the substrate leads to the formation of small sized crystallites. Regarding the optical properties, the films showed good semiconductor properties and a low reflectivity. Introduction Titanium nitride (TiN) thin films were studied by many researchers due to their excellent properties, especially mechanical and tribological properties, corrosion resistance, wear resistance and thermodynamic stability [1–3]. Due to these properties, titanium nitride thin films can be used in a wide range of applications like: diffusion barriers for micro-electric devices, optical coatings with antireflection and antistatic properties, electrodes, biomedicine and hard coatings for tools and so on [4–9]. The most often used methods to obtain titanium nitride films are: reactive magnetron sputtering, laser ablation, ion beam deposition or plasma assisted chemical vapor deposition and so on [10–14]. The physical-chemical and mechanical/tribological properties of titanium nitride films depend on the deposition parameters. In this regard, different researches present the influence of some deposition parameters such as the deposition rate, deposition time, substrate, the heating or the polarization of the substrate on the topographical, mechanical, tribological, adhesion properties for titanium nitride thin films deposited by DC (direct current) magnetron sputtering. All the results are pointing out a change in these properties with the change in deposition parameters. A possible explanation for this change can be the growth of the deposited films after different preferential orientations. The present paper is a study concerning the deposition of titanium nitride thin films by DC magnetron sputtering on silicon substrates at different deposition parameters (substrate Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 134-142 doi: http://dx.doi.org/10.21741/9781945291999-15 135 temperature, substrate bias voltage, deposition time) and the structural and optical characterization of the obtained thin films. Materials and Methods Deposition of titanium nitride thin films The deposition of titanium nitride films was done by direct current reactive magnetron sputtering method, using 99.99 % purity titanium target and silicon Si (100) substrate. The experimental procedure details are presented in previously published work of the authors [4]. The parameters for titanium nitride films deposition were: (i) deposition time (10, 20 and 40 minutes) with the substrate (RT) at room temperature, (ii) deposition time (20 minutes) with the substrate at a temperature of 300 °C and (iii) deposition time (20 minutes) and polarization of the substrate at 40 V and -90 V. These studies were conducted in order to determine the influence of the deposition conditions on the structural and optical properties of titanium nitride films destined for MEMS devices applications. Characterization of titanium nitride thin films X-ray diffraction analysis was carried out with an Inel Equinox 3000 diffractometer using a cobalt radiation (λ1=1.7889 Å, λ2=1.7928 Å). The patterns were evaluated using JPCDS 87-0633. The mean crystallite size and lattice strain were calculated using the Williamson-Hall method. According to this method, the broadening of the diffraction line, β, is given by the sum of the broadening introduced by the crystallite size, βd, and the broadening introduced by the internal strain, βε (equation (1)). These two parameters can be calculated using the equations (2) and (3) as follows [15]: