Optical and chemical characterization of thin TiNx films deposited by DC-magnetron sputtering

Thin titanium nitride (TiN_x) films were deposited on silicon substrates by means of a reactive DC-magnetron plasma. Layers were synthesized under various conditions of discharge power and nitrogen flows in two operation modes of the magnetron (the so-called “balanced” and “unbalanced” modes). The optical constants of the TiN_x films were investigated by spectroscopic ellipsometry (SE). X-ray photoelectron spectroscopy (XPS) was used to determine the relative atomic concentration and chemical states of the TiN_x films. The density and thickness of the films have been investigated by means of grazing incidence X-ray reflectometry (GIXR). The results of the layer analyses were combined with plasma investigations carried out by means of energy resolved mass spectrometry (ERMS) under the same conditions. It is shown that the magnetron mode has a clear influence on the titanium deposition rate and the incorporation of nitrogen into the layers.     

TiNx coatings prepared by d.c. reactive magnetron sputtering

In this paper we describe an investigation of the correlation between the microstructure, morphology and microhardness of non-stoichiometric TiN_x films prepared by reactive d.c. magnetron sputtering in a narrow interval of partial pressure p_N2 of nitrogen. It was found that TiN_x films sputtered at p_N2 < p_N2crit have a quasi-amorphous microstructure and are extremely hard. The results of a detailed experimental study of the films' microstructure, morphology, microhardness and deposition rate are given. It is shown that reactive d.c. magnetron sputtering makes possible the production of TiN_x films with the high deposition rate of 0.5microm min⁻¹.     

Microstructure and tribological performance of CNx–TiNx composite films prepared by pulsed laser deposition

CN_x–TiN_x composite films were prepared on high-speed steel (HSS) substrate by pulsed KrF excimer laser co-deposition process with graphite/Ti combined targets and a substrate temperature of 200 °C. The composition, morphology and microstructure of the films were characterized by energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The adhesion and tribological performance of the films were investigated using a conventional scratch tester and a ball-on-disk tribometer, respectively. In the graphite/Ti range of 0.5–2.0 of the target, TiN_x, a-CN_x and metallic Ti phase were found in the composite films. The TiN_x disappeared in the films at a high graphite/Ti ratio of the target. With increasing the graphite/Ti ratio of the target, the adhesion to substrate of the composite films deteriorated from 46 N to 26 N, and the friction coefficient decreased from 0.23 to 0.17. The composite film deposited at the graphite/Ti ratio of 1.0 showed a low friction coefficient, good adhesion and wear rate of 3.2 × 10⁻⁷ mm³/Nm in humid air.     

X-ray photoelectron spectroscopy analyses of titanium oxynitride films prepared by magnetron sputtering using air/Ar mixtures

X-ray photoelectron spectroscopy (XPS) has been employed to investigate titanium oxynitride (TiN_xO_y) films prepared by d.c. magnetron sputtering using air/Ar mixtures, which allows one to perform the deposition at a high base pressure (1.3 × 10^− 2 Pa) and can reduce substantially the processing time. XPS analyses revealed that all the prepared TiN_xO_y films comprised Ti-N, Ti-N-O, and Ti-O chemical states. When the air/Ar ratio was below 0.3, nitrogen-rich TiN_xO_y films were obtained. As the air/Ar ratio was above 0.4, oxygen-rich TiN_xO_y films were formed. XPS depth profile analyses were also performed in selected specimens. It has been found that at relatively low air/Ar ratios, such as 0.5, the oxygen content of the films increased toward the film/substrate interface and when the air/Ar ratio was higher, TiN_xO_y films with large oxygen content with uniform concentrations were then formed.     

Features of CoSi<Subscript>2</Subscript> phase formation by two-stage rapid thermal annealing of Ti/Co/Ti/Si(100) structures

A method of cobalt disilicide (CoSi₂) layer formation proceeding from a Ti(8 nm)/Co(10 nm)/Ti(5 nm)/Si(100) (substrate) structure prepared by magnetron sputtering is described. The initial structure was subjected to two-stage rapid thermal annealing (RTA) in nitrogen, and the samples after each stage were studied by the time-of-flight secondary-ion mass spectrometry, Auger electron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The RTA-1 stage (550°C, 45 s) resulted in the formation of a sacrificial surface layer of TiN _x O _y , which gettered residual impurities (O, C, N) from inner interfaces of the initial structure. After the chemical removal of this TiN _x O _y layer, the enrichment with cobalt at the RTA-2 stage (830°C, 25 s) led to the formation of a low-resistance CoSi₂ phase.     

The effect of different methods to add nitrogen to titanium alloys on the properties of titanium nitride clad layers

In this investigation, titanium nitride (TiN) reinforcements are synthesized in situ on the surface of Ti–6Al–4V substrates with gas tungsten arc welding (GTAW) process by different methods to add nitrogen, nitrogen gas or TiN powder, to titanium alloys. The results showed that if nitrogen gas was added to titanium alloys, the TiN phase would be formed. But if TiN powder was added to titanium alloys, TiN + TiN_x dual phases would be presented. The results of the dry sliding wear test revealed that the wear performance of the Ti–6Al–4V alloy specimen coated with TiN or TiN + TiN_x clad layers were much better than that of the pure Ti–6Al–4V alloy specimen. Furthermore, the evolution of the microstructure during cooling was elucidated and the relationship among the wear behavior of the clad layer, microstructures, and microhardness was determined.     

Reactive ion plating (RIP) with auxiliary discharge and the influence of the deposition conditions on the formation and properties of TiN films

In this paper we attempt to analyse the processes of reactive evaporation, activated reactive evaporation and reactive ion plating on the basis of earlier theoretical studies. Our initial results concerning the dependence of phase formation on the deposition rate and working gas pressure in reactive evaporation and ion plating indicate that the proposed ideas can in principle be applied and this was also shown analytically by the dependence of the microhardness of TiN films on the pressure. At low partial pressure of nitrogen TiN_x films with a stoichiometric coefficient x near unity are not formed. These near-stoichiometric films are of low hardness. The decrease of microhardness with increasing nitrogen pressure (p 624 × 10^-2 Pa) can be explained by physical effects, such as the inclusion and scattering of gas. Initial studies on the wear properties of such films have indicated their potential in technological applications.     

Effects of rapid thermal treatments on Ti/TiN/Si structures for electrical contacts on silicon

Abstract

A possible new technique for metallisations in Si microelectronics technology has been prepared and characterised. Bilayers of TiN_x/Ti were deposited by sputtering over a Si substrate. The samples were annealed in a rapid thermal processing system, and further analysed using Auger electron spectroscopy and electrical measurements (Schottky barrier height and sheet resistance). Significant differences from the more usual silicidiltion process of a Ti/Si structure have been observed. The silicidation process of the TiN_x/Ti structures is mainly controlled by the presence of the intermediate TiN layer. The final structure was determined to be Si/TiSi_x/TiN_y/TiSi_z.

MST/3336     

Influence of the nonstoichiometry of titanium nitride TiN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> on the degree of its modification with oxygen

We investigate the influence of the nonstoichiometry (the degree of completeness) of titanium nitride TiN on the degree of its modification with oxygen. The completeness of titanium nitride was controlled by changing the nitriding temperature, nitriding time, and partial nitrogen pressure. It is shown that as the completeness of titanium nitride decreases, which leads to an increase in the intensity of oxynitriding, and as the nitrogen content in the ternary compound TiN _x O_{1 – x} decreases, the level of surface hardening of titanium alloys after oxynitriding diminishes.     

Surface chemistry and film growth during TiN atomic layer deposition using TDMAT and NH3

Surface chemistry and film growth were examined during titanium nitride (TiN) atomic layer deposition (ALD) using sequential exposures of tetrakis-dimethylamino titanium (TDMAT) and NH₃. This ALD system is shown to be far from ideal and illustrates many potential problems that may affect ALD processing. These studies were performed using in situ Fourier transform infrared (FTIR) techniques and quartz crystal microbalance (QCM) measurements. Ex situ measurements also analyzed the properties of the TiN ALD films. The FTIR studies revealed that TDMAT reacts with NH_x* species on the TiN surface following NH₃ exposures to deposit new Ti(N(CH₃)₂)_x* species. Subsequent NH₃ exposure consumes the dimethylamino species and regenerates the NH_x* species. These observations are consistent with transamination exchange reactions during the TDMAT and NH₃ exposures. QCM studies determined that the TDMAT and NH₃ reactions are nearly self-limiting. However, slow continual growth occurs with long TDMAT exposures. In addition, the TiN ALD growth rate increases progressively with growth temperature. The resistivities of the TiN ALD films were ?10⁴ μΩ cm and the densities were ?3 g/cm³ corresponding to a porosity of ∼40%. The high porosity allows facile oxidation of the TiN films and lowers the film resistivities. These high film porosities will seriously impair the use of these TiN ALD films as diffusion barriers.     

Sinterability and properties of Ti(N1−x,O x ) y -(V,Ta)C-Ni sintered alloys having a golden colour

The effect of oxygen and carbide addition on the sinterability of TiN _y (0.42<y<1)-Ni alloys, in which part of the nitrogen is replaced by oxygen was investigated. It was found that sinterability increased as the oxygen and carbide content increased, but the strength of the resultant sintered alloys was significantly reduced due to the presence of Ni₃Ti and Ti₂O₃ phases when the oxygen content exceeded 50 mol %. The sintered alloy with the highest hardness was found whenx=0.7,y=0.78 and the (V,Ta)C content was 18% by weight and this alloy was characterized by having a low density, good corrosion resistance and the colour of gold.     

Oxidation behavior of (Ti1 − xAlx)N films perpared by r.f. reactive sputtering

(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 °C. We have investigated the effect of Al content on the oxidation resistance of (Ti_{1 − x}Al_x)N films prepared by r.f. reactive sputtering.(Ti_{1 − x}Al_xN films (O ≤ x ≤ 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N₂ (5 N). The flow rate of Ar and N₂ gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 900 °C and then subjected to X-ray diffractometer and Auger depth profiling.The as-deposited (Ti_{1 − x}Al_x)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 °C annealing, even if the Al content was increased up to 0.55.     

Electron cyclotron resonance (ECR) plasma-enhanced chemical vapour deposition of silicon dioxide on strained-SiGe films using tetraethylorthosilicate

Silicon dioxide films on strained Si_1−x Ge _x have been deposited by electron cyclotron resonance (ECR) plasma-enhanced chemical vapour deposition technique using tetraethylorthosilicate (TEOS) at room temperature. The deposition rate as a function of time and substrate temperature has been studied. MOS capacitors fabricated using deposited oxides have been used to characterize the electrical properties of silicon dioxide films. Deposited oxide film shows its suitability for microelectronic applications.     

The microstructure and wettability of the TiOx films synthesized by reactive DC magnetron sputtering

Different chemical state of titanium oxide films were deposited on commercially pure Ti (CP Ti) by reactive DC magnetron sputtering under different oxygen flow rates to examine a possibility of their applications to endovascular stents. The chemical composition and crystal structure of the obtained films were analyzed by XPS and XRD, respectively. In dependence on the deposition parameters employed, the obtained films demonstrated different mixture of anatase TiO₂, Ti₂O₃, TiO and Ti. The wettability of the films was measured by the water contact angle variation. By formation of titanium oxide film on CP Ti, contact angle was decreased. In order to modify and control the surface wettability, the resultant TiO_x films were etched subsequently by different plasma. The wettability was influenced by etched process according to the decreased contact angle values of etched TiO_x film. Furthermore, TiO_x films became highly hydrophilic by ultraviolet (UV) irradiation, and returned to the initial relatively hydrophobic state by visible-light (VIS) irradiation. The wettability of the TiO_x film was enabled to convert between hydrophilic and hydrophobic reversibly by alternative UV and VIS irradiation. By adjusting deposition parameter and further modification process, the wettability of the TiO_x films can be changed freely in the range of 0–90°.     

CN<Subscript>x</Subscript>/TiN<Subscript>y</Subscript> films prepared by ion-beam sputtering

CN _x /TiN _y multilayers were prepared by ion-beam sputtering and analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX). EDX results show that the atom ratios of [N]/([C] + [N] + [Ti]) in the multilayers vary from 20 at.% to 41 at.%. XPS analysis presents that the N content of the CN _x layer in CN _x /TiN _y is about 32.18 at.%. The nature of chemical bonding of the CN _x layer in CN _x /TiN _y was also analyzed. The X-ray and electron diffraction analyses suggest that three kinds of C₃N₄ phases, such as -C₃N₄, graphite-C₃N₄ and cubic-C₃N₄, are embodied in the multilayers. In CN _x /TiN _y bilayers, a hetero-epitaxial relationships, of (1 1 2) cubic-C₃N₄//(1 1 13) Ti₂N, and [42 3¯] cubic-C₃N₄//[1 1¯ 0] Ti₂N, was observed between cubic-C₃N₄ and Ti₂N.     

Synthesis of titanium nitride by a spark-discharge method in liquid ammonia

Titanium nitride powders were synthesized by the spark-discharge method in liquid ammonia at — 78 to 130 °C and 3.5–10.5 kV discharge voltage using titanium pellets as the starting materials. Titanium nitride possessing nitrogen defect, TiN_1–x (x0.5), was obtained as the main product, together with small amounts of -Ti alloyed with nitrogen. The increase in temperature of the liquid ammonia resulted in an increase in the titanium nitride content in the product but a decrease in the powder production rate. By calcining the mixed powders of TiN_1–x and -Ti in a nitrogen atmosphere around 1200 °C, stoichiometric TiN was obtained as single phase.     

Bulk and interface properties of low-temperature silicon nitride films deposited by remote plasma enhanced chemical vapor deposition

Hydrogenated silicon nitride (a-SiN_x:H) films were deposited at temperatures ranging from 50 to 300 °C with remote plasma enhanced chemical vapor deposition (RPECVD) from NH}_{3 and SiH}_{4. The effect of the operating variables, such as deposition temperature and especially the partial pressure ratio of reactant (R=NH₃/SiH₄) on the properties of the Sa-SiN_x:H interface was investigated. The H^* radical was dominantly observed and the deposition rate was proportional to the NH^* radical concentration. The density of highly energetic N ₂ ^* radicals increased in the high plasma power regime in which the film surface was roughened, but they promote surface reactions even at low temperature. The refractive index was more closely related to the film stoichiometry than film density. The interface trap density is related to the amount of silicon intermediate species and Si–NH bonds at the Si/SiN_x:H interface and it can be minimized by reducing the intermediate Si species and Si–NH bonding state. The films showed a midgap interface trap density of 2 × 10¹¹ - 2 × 10¹²cm^-2. © 2001 Kluwer Academic Publishers     

Structural evolution of Ti-Al-Si-N nanocomposite coatings

Ti-Si-Al-N films were prepared by rf reactive magnetron sputtering, in static and rotation modes, using a wide range of different deposition conditions, which created conditions to obtain Ti-Al-Si-N coatings with different structural arrangements.Films prepared below a critical nitrogen flow, under conditions out of thermodynamic equilibrium, revealed a preferential growth of an fcc (Ti,Al,Si)N_x compound with a small N deficiency. With nitrogen flow above that critical value, the reduction of the lattice parameter was no longer detected. However, a thermal annealing showed that a complete thermodynamically driven segregation of the TiN and Si₃N₄ phases was not yet obtained. The segregation upon annealing induced a self-hardening and showed a multiphase system, where the crystalline TiN, (Ti,Al)N and (Ti,Al,Si)N_x phases were identified by X-ray diffraction. This behavior is due to the de-mixing of the solid solution associated to a small N deficiency.     

Ti2Al(O,N) formation by solid-state reaction between substoichiometric TiN thin films and Al2O3 (0001) substrates

Titanium nitride TiN_x (0.1 ≤ x ≤ 1) thin films were deposited onto Al₂O₃(0001) substrates using reactive magnetron sputtering at substrate temperatures (T_s) ranging from 800 to 1000 °C and N₂ partial pressures (pN₂) between 13.3 and 133 mPa. It is found that Al and O from the substrates diffuse into the substoichiometric TiN_x films during deposition. Solid-state reactions between the film and substrate result in the formation of Ti₂O and Ti₃Al domains at low N₂ partial pressures, while for increasing pN₂, the Ti₂AlN MAX phase nucleates and grows together with TiN_x. Depositions at increasingly stoichiometric conditions result in a decreasing incorporation of substrate species into the growing film. Eventually, a stoichiometric deposition gives a stable TiN(111) || Al₂O₃(0001) structure without the incorporation of substrate species. Growth at T_s 1000 °C yields Ti₂AlN(0001), leading to a reduced incorporation of substrate species compared to films grown at 900 °C, which contain also Ti₂AlN(101?3) grains. Finally, the Ti₂AlN domains incorporate O, likely on the N site, such that a MAX phase oxynitride Ti₂Al(O,N) is formed. The results were obtained by a combination of structural methods, including X-ray diffraction and (scanning) transmission electron microscopy, together with spectroscopy methods, which comprise elastic recoil detection analysis, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy.     

Orientation of the BSCCO films prepared by low-pressure single-aerosol source metallorganic chemical vapour deposition

Thin films (0.7–0.8 μm) of Bi₂Sr₂CaCu₂O_x were deposited by low-pressure metallorganic chemical vapour deposition with a single aerosol source. The influence of the deposition parameters on the orientation of the films was studied. It was established that low deposition rate, high deposition temperature and the presence of the liquid phase resulted in films with predominant c-orientation.