TiNx Films Research Articles

INFLUENCE OF THE RATIO OF GASE CONSUMPTION N<sub>2</sub>/Ar AND MAGNETRON POWER ON THE DENSITY AND STOICHIOMETRIC COMPOSITION OF TIN<sub>X</sub> FILMS SYNTHESIZED BY MAGNETRON SPUTTERING METHOD

The films of titanium nitride were deposited by direct current magnetron sputtering on the surface of singlecrystalline silicon samples in an Ar-N2 atmosphere for use as a diffusion barrier. The thickness and density of films were measured by X-ray reflectometry. The design of the MAGNA TM-200-01 installation has been changed to increase the supply of nitrogen into the chamber. The influences of sputtering conditions, including the flow rate of nitrogen and argon gases and their N2 /Ar ratios in the range of 1–60 in the chamber, magnetron power of 690–1400 W on the formation of TiNx films, their density and stoichiometric composition, were studied. It is shown that the value of x is affected not only by the N2 /Ar gas flow rate ratio, but also by the magnetron power. At the sputtering parameters 1200 W, N2 /Ar = 30, 0.8 Pa, 320 s and 100°C, a maximum density of 5.247 g/cm3 of a film was achieved, which corresponds to the composition TiN0.786 = Ti56N44. The presence of nanocrystalline film of titanium nitride and the absence of a nanocrystalline titanium phase were confirmed by photographic X-ray diffraction. It was found that for the synthesis of titanium nitride as close as possible to the stoichiometric composition TiN0.770 - TiN0.786, it is necessary to use magnetron power in the range of 900–1200 W, nitrogen rate of 30 cm3 /min with low argon flows of 1–5 cm3 /min.

Engineering Carrier Density and Effective Mass of Plasmonic TiN Films by Tailoring Nitrogen Vacancies.

The introduction of nitrogen vacancies has been shown to be an effective way to tune the plasmonic properties of refractory titanium nitrides. However, its underlying mechanism remains debated due to the lack of high-quality single-crystalline samples and a deep understanding of electronic properties. Here, a series of epitaxial titanium nitride films with varying nitrogen vacancy concentrations (TiNx) were synthesized. Spectroscopic ellipsometry measurements revealed that the plasmon energy could be tuned from 2.64 eV in stoichiometric TiN to 3.38 eV in substoichiometric TiNx. Our comprehensive analysis of electrical and plasmonic properties showed that both the increased electronic states around the Fermi level and the decreased carrier effective mass due to the modified electronic band structures are responsible for tuning the plasmonic properties of TiNx. Our findings offer a deeper understanding of the tunable plasmonic properties in epitaxial TiNx films and are beneficial for the development of nitride plasmonic devices.

Titanium Nitride as a Plasmonic Material from Near-Ultraviolet to Very-Long-Wavelength Infrared Range.

Titanium nitride is a well-known conductive ceramic material that has recently experienced resumed attention because of its plasmonic properties comparable to metallic gold and silver. Thus, TiN is an attractive alternative for modern and future photonic applications that require compatibility with the Complementary Metal-Oxide-Semiconductor (CMOS) technology or improved resistance to temperatures or radiation. This work demonstrates that polycrystalline TiNx films sputtered on silicon at room temperature can exhibit plasmonic properties continuously from 400 nm up to 30 μm. The films’ composition, expressed as nitrogen to titanium ratio x and determined in the Secondary Ion Mass Spectroscopy (SIMS) experiment to be in the range of 0.84 to 1.21, is essential for optimizing the plasmonic properties. In the visible range, the dielectric function renders the interband optical transitions. For wavelengths longer than 800 nm, the optical properties of TiNx are well described by the Drude model modified by an additional Lorentz term, which has to be included for part of the samples. The ab initio calculations support the experimental results both in the visible and infra-red ranges; particularly, the existence of a very low energy optical transition is predicted. Some other minor features in the dielectric function observed for the longest wavelengths are suspected to be of phonon origin.

Study on the resistivity and infrared emissivity of TiNx films at different sputtering power

TiNx films with low infrared emissivity were prepared using DC reactive magnetron sputtering technique. The influence of sputtering power (50, 80, 100, and 200 W) on the morphology, structure, adhesion force, resistivity and infrared emissivity was investigated systematically. The thickness of the prepared TiNx films was in the range of 381–987 nm. The films grew with preferred orientation of (200) plane at lower sputtering power, while the preferred orientation was (220) plane at higher sputtering power. The N/Ti stoichiometry ratio increased from 0.67 to 0.96 with the increase of sputtering power, and the deposited TiNx thin films were off stoichiometry. Due to more formation of bonds of Ti–N in TiNx crystal, the adhesion force increased with increasing of sputtering power. The resistivity and infrared emissivity of TiNx films first deceased, and then increased with the increase of sputtering power. Defects in TiNx films prepared at 50 W led to high resistivity and infrared emissivity. The lattice distortion caused by Ti atoms was considered to play an important role in the increase of the resistivity of TiNx films at 200 W. The decrease of carrier density caused by decreased nitrogen vacancies should be the reason for the increase of the infrared emissivity of TiNx films at 80–200 W.

Production Strategies of TiNx Coatings via Reactive High Power Impulse Magnetron Sputtering for Selective H2 Separation.

This scientific work aims to optimize the preparation of titanium nitride coatings for selective H2 separation using the Reactive High Power Impulse Magnetron Sputtering technology (RHiPIMS). Currently, nitride-based thin films are considered promising membranes for hydrogen. The first series of TiNx/Si test samples were developed while changing the reactive gas percentage (N2%) during the process. Obtained coatings were extensively characterized in terms of morphology, composition, and microstructure. A 500 nm thick, dense TiNx coating was then deposited on a porous alumina substrate and widely investigated. Moreover, the as-prepared TiNx films were heat-treated in an atmosphere containing hydrogen in order to prove their chemical and structural stability; which revealed to be promising. This study highlighted how the RHiPIMS method permits fine control of the grown layer’s stoichiometry and microstructure. Moreover, it pointed out the need for a protective layer to prevent surface oxidation of the nitride membrane by air and the necessity to deepen the study of TiNx/alumina interface in order to improve film/substrate adhesion.

Improved infrared emissivity of diamond-like carbon sandwich structure with titanium nitride metallic interlayer

In this study, a novel titanium nitride (TiNx) based low-emissivity (low-e) coating of which dielectric layer is a diamond-like carbon (DLC) film deposited as a three-layer stack on a glass substrate using direct current (DC) magnetron sputtering technique. For TiNx thin films, the sputtering power was changed between 25 W and 135 W. Influences of the sputtering power on phase, microstructure, bonding properties, resistivity, optical properties and infrared emissivity of the films were characterized by UV–VIS–NIR spectrophotometery, XRD, SEM, AFM, XPS, four-point probe and FTIR, respectively. It was observed that the metallic character, crystallinity, stoichiometry, reflectance in visible region as well as infrared emissivity of TiNx films were significantly affected by sputtering power. TiNx films deposited at higher plasma power had a more significant negative real part of dielectric function, exhibited better crystallinity, were more stoichiometric, had a lower resistivity and a lower infrared emissivity. The emissivity of the films decreased from 0.52 to 0.17 with increased sputtering power from 25 W to 135 W. The designed low-e coating with a structure of DLC/TiNx/DLC in the current study had an emissivity of 0.49. This coating had an optical transmission of approximately 45% over the visible spectra. These results suggest that the DLC/TiNx/DLC structure could be a good candidate for being used in low-e applications on glasses.

Effect of bias on structure mechanical properties and corrosion resistance of TiNx films prepared by ion source assisted magnetron sputtering

Titanium nitride (TiNx) films were deposited on 304 stainless steel and silicon (100) wafers by ion source assisted magnetron sputtering. The effect of substrate bias voltage on the preparation and properties of TiNx films was investigated. The results show that as the substrate bias voltage increases from 0 V to −400 V, the deposition rate of TiNx film decreases significantly and the density increases, which can be attributed to the re-sputtering effect at high ion bombardment. The texture of TiNx films varies gradually from (111) to (200) with the increase of energy delivered into the growing film. The hardness of the film deposited under −200 V bias voltage reaches the maximum value, 12.9 GPa. Meanwhile, the toughness and corrosion resistance of the film reach a maximum at a bias voltage of −400 V. In conclusion, the density, hardness, toughness and corrosion resistance of TiNx films can be increased by changing the substrate bias voltage.

Thickness dependent chemical and microstructural properties of DC reactive magnetron sputtered titanium nitride thin films on low carbon steel cross-section

Polished samples of low carbon steel (LCS) rod cross-sections were sputtered with different thicknesses of TiNx thin film using DC reactive magnetron sputtering technique. While other process parameters such as target power (200W), substrate position (150mm) and sputtering pressure (1.33Pa) were kept constant during the deposition, the deposition time was varied from 5 to 20min. Physical and chemical characterizations of the samples were done using Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and optical microscopy. Vickers micro-hardness tester was used for the hardness test. The optimum value of the Vickers hardness was found to be 267.9 for the film deposited at 20min. The inter-planar spacing was found to be from 2.0362Å to 2.0890Å, while corresponding lattice parameter was calculated to be from 4.0724Å to 4.1780Å. Scanning electron microscopy observation of the films gave an indication of fine-grained microstructure, which confirms the good adhesion and hardness properties of titanium nitride layer on the LCS substrate. The XRD spectra show that the multiphase reflections TiO2 (110) and TiN (111) for thinner film samples which shift to a preferred orientation (200) for thicker films, indicating a largely TiNx phase. This strongly suggest remarkable changes in crystal orientations of the TiNx films with deposition time. Ion beam (RBS) results showed increase in amount of nitrogen contents (47–64%) in TiNx films with thickness and deposition time.

Substrate temperature effects on infrared emissivity of TiNx films

ABSTRACTTiNx films were deposited using direct current reactive magnetron sputtering on glass substrates, and the variation of resistivity and infrared emissivity of TiNx films deposited at different substrate temperatures was investigated. The N/Ti ratios of prepared films were off-stoichiometric, and reached the highest value 0.97 at 350°C. The results showed that substrate temperature had an important role in regulating the resistivity and infrared emissivity of TiNx films, and the change in resistivity of the films was consistent with their infrared emissivity. As the substrate temperature increased from 25 to 350°C, the resistivity of the films decreased from 15.7 × 103 to 0.9 × 103 μΩ cm. Infrared emissivity in the wavelength of 3–5 μm decreased from 0.55 to 0.29, and the value in the wavelength of 8–14 μm dropped from 0.54 to 0.27.

Titanium nitride thin film for temperature sensing and its conductive mechanism in the cryogenic region

Titanium nitride (TiNx) thin films were deposited by DC magnetron sputtering on polished and oxidized silicon wafers under different N2 flow rates, and temperature sensors based on the TiNx films were fabricated. The performance of three typical sensors were measured in the temperature range of 4.2 K–300 K, and the results indicate that TiNx thin film sensors are suitable for cryogenic temperature measurements. Furthermore, the conduction mechanism of TiNx thin film in the temperature range of 4.2 K–300 K was studied for the first time, and it can be described by an impurity conduction mechanism. Finally, the contribution of the grain and grain boundary on the film resistance and temperature coefficient of resistance was studied by AC impedance analysis, and the characterization result indicates that the impurity conduction mechanism of the TiNx thin film is dominated by the grain.

Effect of N2 flow rate on electromagnetic interference shielding effectiveness of TiNx films

TiNx films with different nitrogen contents were fabricated using direct current reactive magnetron sputtering. Influence of N2 flow rate on the resistivity and electromagnetic interference (EMI) shielding effectiveness (SE) of TiNx films was studied. The EMI SE of TiNx films was found to be related with the resistivity. With the rise of N2 flow rate, the resistivity of TiNx films increased, while the EMI SE decreased. When the N2 flow rate was 1 sccm, the EMI SE of TiNx films was over 20 dB with the thickness of 1.47 µm, which was much smaller than the thickness of the presently known EMI-shielding materials. The results indicated that TiNx films could be applied as ultrathin thickness, lightweight, and design flexibility shielding materials.

Low temperature thermal ALD TaNx and TiNx films from anhydrous N2H4

Thermal ALD of TaNx and TiNx films was performed using hydrazine (N2H4) as a reactive N-containing source. Ultralow temperature (100 °C and 300 °C) growth of TaNx was observed using N2H4 and tris(diethylamido)(tert-butylimido) tantalum (TBTDET); XPS showed nearly stoichiometric Ta3N5 films were deposited with below 10% O and 5% C incorporation. Stoichiometric TiNx films grown at 300 °C with tetrakis(dimethylamido) titanium (TDMAT) showed an RMS roughness below 2 nm consistent with good nucleation density. High conductivity nitride films were grown by a thermal low-temperature TiNx ALD process using anhydrous N2H4 and titanium tetrachloride (TiCl4) from 300 to 400 °C; uniform, nearly stoichiometric films of 0.44 nm RMS roughness were deposited. Compared to NH3 grown films, XPS confirmed N2H4 grown films contained fewer O, C, and Cl impurities consistent with lower resistivities being observed with N2H4. The data is consistent with N2H4 serving as a reducing agent and a good proton donor to Ta and Ti ligands.

(Invited) Low Temperature Thermal ALD TiNx and TaNx Films from Anhydrous N2H4

Titanium nitride (TiN) has been extensively studied in semiconductor devices because of its ideal thermal, mechanical, and electrical properties, along with its ability to act as a diffusion barrier to WF6 during W metal fill. Similarly, tantalum nitride (TaN) is being utilized as a diffusion barrier on SiOCH to Cu, as Cu can readily diffuse, causing device reliability issues. Metal halide precursors are typically preferred over organometallic grown films when there is no concern about substrate etching; however, organometallic-grown films usually contain higher levels of carbon and oxygen contamination, which has been correlated with an increase in film resistivity. Plasma enhanced-ALD TiN has been shown to achieve optimal growth rates with lower contamination at temperatures below 350°C, but the film and underlying substrate can suffer from plasma-induced damage. In this study, low temperature thermal ALD TiNx from anhydrous N2H4 and TiCl4 was performed on SiO2, and the deposited films were studied using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). TaNx films were grown utilizing N2H4 and tris(diethylamido)(tertbutylimido) tantalum(V) (TBTDET) and characterized similarly. In situ XPS was employed to demonstrate pulse saturation during ALD for TiCl4 + N2H4 à TiNx. AFM showed that 40 cycles of TiCl4 + N2H4 at 300°C produces pinhole-free, conformal films. Additionally, the effect of air exposure on TiNx films was studied; O attacked the TiNx film, evidenced by observing a 1.5 eV BE shift of the Ti 2p 3/2 peak. A comparison was made of the TiNx films grown at 300ºC and 400ºC with NH3 vs. N2H4; even at 400ºC there was approximately 2x more O and C and 50% more Cl in NH3 grown films. Furthermore, N2H4 films showed lower resistivities, attributed to lower contamination and likely better nucleation density, especially at 300oC. In situ XPS was also used to study TaNx films grown using TBTDET and N2H4. To study the nucleation on SiO2, an initial TBTDET exposure was performed; the Ta 4d peak position confirmed the nucleation and formation of Si-O-Ta bonds. After subsequent cycles, the Ta 4d peak shifts ~2eV toward lower binding energy upon forming Ta-N bonds. While the films were of extremely high purity with stoichiometry resembling Ta3N5, the N2H4 was unable to reduce the Ta oxidation state from films grown between 100oC and 300oC showing the need for some metals for the use of low oxidation state precursors or a stronger, highly energetic reducing agent. These studies with anhydrous N2H4 show the potential to form high purity barrier layers using low temperature thermal ALD as long as highly energetic reactants are used.

Substrate and annealing temperature dependent electrical resistivity of sputtered titanium nitride thin films

We have studied the electrical resistivity and the temperature coefficient of resistance (TCR) of titanium nitride (TiNx) thin films deposited by radio-frequency (RF) reactive magnetron sputtering from a high purity titanium target in a nitrogen-argon gas mixture environment with high nitrogen-to-argon ratio (20:1). The electrical resistivity and TCR are measured from room temperature to 500 °C for films deposited with substrate temperatures of 25 °C, 350 °C and 600 °C. After deposition, some films are annealed at 600 °C for four hours either with or without breaking the vacuum. The structural stability of the films was examined by measuring electrical resistivity from room temperature to 500 °C repeatedly up to four cycles. Selected films were further characterized by Rutherford backscattering, X-Ray diffraction, and Raman spectroscopy. Our results show that RF sputtered TiNx films with good electrical resistivity and temperature-stable TCR for high-temperature applications of conductive diffusion barrier and temperature sensing can be produced. We conclude that high substrate temperature, high annealing temperature, and annealing without breaking the vacuum yield optimal structural stability and electrical resistivity. High mass density is also important to prevent oxidation and degradation of electrical performance.

Hard TiN2 dinitride films prepared by magnetron sputtering

This letter reports on the formation of hard TiN2 dinitride films prepared by magnetron sputtering. TiN2 films were reactively sputtered in an Ar + N2 gas mixture using a pulsed dual magnetron with a closed magnetic field B. The principle of the formation of TiN2 films by magnetron sputtering is briefly described. The stoichiometry x = N/Ti of the TiNx films was controlled by deposition parameters, and its maximum value of x = 2.3 was achieved. For the first time, a possibility to form the TiN2 dinitride films by magnetron sputtering has been demonstrated. The mechanical properties of sputtered films were investigated in detail.

Research on optical reflectance and infrared emissivity of TiNx films depending on sputtering pressure

TiNx thin films were deposited on glass substrates using direct current reactive magnetron sputtering, and effects of sputtering pressure on optical reflectance and infrared emissivity of TiNx films were studied. The results indicated that sputtering pressure was a key factor to affect the optical reflectance and infrared emissivity of TiNx films in this study. When sputtering pressure varied from 0.3 Pa to 1.2 Pa, an average reflectance of less than 25% in the visible range was obtained for the prepared films. With the working pressure rise, the resistivity of TiNx films went up. Meanwhile, the infrared emissivity of the films increased. As sputtering pressure was 0.3 Pa, the infrared emissivity in the wavelength of 3–5 and 8–14 μm of TiNx film with dark color and low optical reflectance was less than 0.2.

Influence of the nitrogen flow rate on the infrared emissivity of TiNx films

TiNx films were deposited on glass substrates by DC reactive magnetron sputtering technique. The influence of N2 flow rates (1, 2, 4, and 20 sccm) on the structure, resistivity, and infrared emissivity of TiNx films was studied. The XRD patterns showed that the films deposited at 1, 2, and 4 sccm were composed of TiN phase with a faced-centered cubic crystal structure. As the N2 flow rate rose from 1 to 4 sccm, the preferred orientation of the films altered from (1 1 1) to (2 0 0) plane. Upon further increased to 20 sccm, the XRD peaks were almost indiscernible. The XPS analysis revealed that the TiNx films were nitrogen deficient, and titanium oxy-nitride and TiO2 phase formed in the films. The N/Ti stoichiometry ratio increased from 0.69 to 0.98 with the N2 flow rate rise. The resistivity variation was consistent with the infrared emissivity in the band of 8–14 μm of TiNx films. As the N2 flow rate rose from 1 to 2 sccm, the resistivity and emissivity of the TiNx films went up, and then dropped with the N2 flow rate further increase.

Enhancement of Mechanical Property on Sputtered TiNx Films with Various Deposition Temperatures

Enhancement of Mechanical Property on Sputtered TiN<i>_x</i> Films with Various Deposition Temperatures

Effect of energy on structure, microstructure and mechanical properties of hard Ti(Al,V)Nx films prepared by magnetron sputtering

The article reports on the effect of the energy delivered into the growing film by bombarding ions ℰbi and/or fast neutrals ℰfn on its structure, microstructure and mechanical properties, and resistance to cracking. The effect of the total delivered energy ℰ=ℰbi+ℰfn on the film properties is demonstrated on the Ti(Al,V)Nx films deposited by reactive magnetron sputtering. The films were sputtered onto Si(111) and Mo substrates in a mixture Ar+N2 gases by a dual magnetron with closed magnetic field and equipped with TiAlV (6at.% Al, 4at.% V) alloy targets. It was shown that (1) The energy ℰ is a key parameter controlling the physical and mechanical properties, and the resistance to cracking of sputtered Ti(Al,V)Nx films, (2) The structure of Ti(Al,V)Nx films varies from TiN(200) to TiN(220) with increasing energy ℰ, (3) The Ti(Al,V)Nx films with high ratio H/E⁎ ≥0.1, high elastic recovery We ≥60% and dense voids-free microstructure exhibit an enhanced resistance to cracking and can be produced only in the case when a sufficient energy ℰ is delivered into the growing film either by bombarding ions or by bombarding fast neutrals and (4) The energy ℰfn makes it possible to sputter crystalline films onto dielectric substrates held at a floating potential Us=Ufl.

Titanium and titanium nitride thin films grown by dc reactive magnetron sputtering Physical Vapor Deposition in a continuous mode on stainless steel wires: Chemical, morphological and structural investigations

Ti and TiN thin films (50–140nm thick) are grown by dc reactive magnetron sputtering PVD in an inverted cylindrical magnetron (ICM) thanks to an original industrial process corresponding to a continuous reactive deposition on moving stainless steel wires. Thin films are fully characterized by X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy coupled with Energy Dispersive Spectroscopy and Orientation Phase Mapping. The stoichiometry of TiN is adjusted thanks to N2 flow. At the beginning of poisoned mode, golden stoichiometric TiN thin films are obtained. In the metallic mode, greyish TiNx films are grown whereas at higher N2 flow, TiNxOy films are synthetized with preferential O incorporation instead of N enrichment. Grain orientation maps reveal that Ti and TiN thin films are highly polycrystalline: Ti films have an equiaxis morphology whereas TiN thin films have a tendency to present 〈111〉 columnar grains with 〈001〉 oriented grains at the nucleation step. Finally, a low temperature of growth (of about 350°C and <650°C) is needed in order to prevent chemical diffusion from the stainless steel substrate into the rich-titanium films.