Synthesis and study of highly dense and smooth TiN thin films

Abstract

This study aims towards a systematic reciprocity of the tunable synthesis parameters - partial pressure of N2 gas, ion energy (Ei) and Ti interface in TiN thin film samples deposited using ion beam sputtering at ambient temperature (300 K). At the optimum partial pressure of N2 gas, samples were prepared with or without Ti interface at Ei = 1.0 or 0.5 keV. They were characterized using x-ray reflectivity (XRR) to deduce thickness, roughness and density. The roughness of TiN thin films was found to be below 1 nm, when deposited at the lower Ei of 0.5 keV and when interfaced with a layer of Ti. Under these conditions, the density of TiN sample reaches to 5.80(±0.03) g cm−3, a value highest hitherto for any TiN sample. X-ray diffraction and electrical resistivity measurements were performed. It was found that the cumulative effect of the reduction in Ei from 1.0 to 0.5 keV and the addition of Ti interface favors (111) oriented growth leading to dense and smooth TiN films and a substantial reduction in the electrical resistivity. The reduction in Ei has been attributed to the surface kinetics mechanism (simulated using SRIM) where the available energy of the sputtered species (<Esp>) leaving the target at Ei = 0.5 keV is the optimum value favoring the growth of defects free homogeneously distributed films. Secondary ion mass spectroscopy depth profile measurements confirm the uniform distribution of N and Ti across the depth of a sample. The electronic structure of samples was probed using N K-edge and Ti L-edge absorption spectroscopy and the information about the crystal field and spin-orbit splitting confirmed TiN phase formation. In essence, through this work, we demonstrate the role of <Esp> and Ti interface in achieving highly dense and smooth TiN thin films with low resistivity without the need of a high temperature or substrate biasing during the thin film deposition process.