TiB2 Films Research Articles

Dimensional dependence of electric resistance of thin TiB2 films

The dimensional effect of electrical resistance in thin films of TiB2 has been studied. Experimental results were processed within the framework of the Fuchs-Sondheimer theory. This has enabled us to estimate the conductivity parameters in the diffuse surface scattering approximation.

Microstructure and properties of nitride and diboride hard coatings deposited under intense mild-energy ion bombardment

The concept of low or mildly energetic but intense ion bombardment was applied to coatings based on the nitrides and diborides of the transition metals titanium and zirconium. Coatings were deposited using non-reactive unbalanced d.c. magnetron sputtering. Films were bombarded by means of argon ions with varying energy (Ei) and intensity (ion/atom flux ratio Ji/Ja). Fracture cross-sections revealed the existence of the transition zone (zone T) structure for all coatings. TiN and ZrN coatings, which are exposed to low energetic bombardment, revealed a preferred growth on (111) lattice planes. Mildly energetic and intense bombardment resulted in a shift of the preferred orientation to (200). TiB2 and ZrB2 films grow more or less randomly under low energetic and less intense bombardment. However, they displayed a preferred (001) orientation with increasing intensity of the ion irradiation. The hardness of the coatings increased by the effect of both mildly energetic and intense ion bombardment, mainly as a result of reduced film porosity and to a lesser extent due to reduced crystal size and increasing film stresses.

Process‐Structure‐Reflectance Correlations for TiB2 Films Prepared by Chemical Vapor Deposition

The process‐structure‐reflectance interrelationships for TiB2 films prepared by CVD were determined using statistically designed experiments. A hot wall CVD reactor employing graphite substrates and the TiCl4+ BCl3+ H2 reagent system were used at pressures of 2.7 and 6.7 kPa. Single‐phase polycrystalline TiB2 films were obtained. An increasing percentage of the grains were oriented with their (001) planes parallel to the substrate as the deposition temperature was increased and as the BCl3:TiCl4 ratio decreased. Grain size increased from ∼0.5 to 3 µm as the deposition temperature was increased from 900° to 1100°C and as the coating rate was decreased from 0.6 to 0.1 µm/min. Fine‐grained, smooth, highly reflective films were obtained at low deposition temperatures and high BCl3:TiCl4 ratios.

Features of Fracture Surface and Grain Boundary Structure of Boride/Nitride Materials

ABSTRACTNanostructured bulks and films of TiB2, TiN, AIN, Ti(B,N), and (Ti,Al)N prepared by high pressure sintering and nonreactive magnetron sputtering accordingly. Fracture surfaces and structure of grain boundaries have been investigated by high-resolution scanning and transmission electron microscopy as well as by atomic force microscopy. The revealing of transgranular fracture, homogeneous and inhomogeneous deformation, and the availability of dislocations and amorphous phases in structure are discussed.

TiB2as a Diffusion Barrier for Cu/<si> Metallization

AbstractTiB2, films deposited by co-sputtering from a boron and a TiB, target are evaluated as the diffusion barrier for Cu metallization. Material characteristics of the TiB, films and metallurgical interactions of the Cu/TiB2/<Si> system annealed at 400−700°C for 30 min, in a 80%Ar+20%H2 flow, were investigated by glancing angle X-ray diffraction, Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). Sheet resistance was measured for electrical characterization.The composition and resistivity of the sputtered TiB1 films varied with the bias applied on the substrate. To obtain a low film resistivity, a negative bias of 200V was applied during sputtering. The resulting TiB2 film is nanocrystalline with a resistivity of 300 μΩcm. After copper deposition, the Cu/TiB2/<Si> samples have a constant sheet resistance after annealing up to 600°C for 30min. The overall sheet resistance of the sample increases by five orders of magnitude after annealing at 700°C, and scanning electron micrographs reveal that the sample surface is severely deteriorated after annealing at 700°C.

Refractory metal boride ohmic contacts to P-type 6H-SiC

Ohmic contacts have been fabricated on p-type 6H-SiC (1.3×1019 cm−3) using CrB2, W2B, and TiB2. The boride layers (∼100–200 nm) were sputter-deposited in a system with a base pressure of 3×10−7 Torr. Specific contact resistances were measured using the linear transmission line method, and the physical properties of the contacts were examined using Rutherford backscattering spectrometry. All as-deposited contacts exhibited rectifying characteristics. Ohmic behavior was observed following short anneals (2–10 min) at 1100°C and 5×10−7 Torr. Current-voltage characteristics were linear for CrB2 and W2B and quasi-linear for TiB2. The lowest values of the specific contact resistance (rc in Ω-cm2) measured at room temperature for CrB2 and W2B were 8.2×10−5 and 5.8×10−5, respectively. The specific contact resistance for TiB2 was not determined accurately. Longer anneals (30 min for W2B and 90 min for CrB2) reduced the room temperature values of rc to 6.1×10−5 for W2B and 1.9×10−5 for CrB2. Backscattering spectra revealed substantial concentrations of oxygen in all as-deposited boride films. The short anneal cycle removed the oxygen in the CrB2 films and reduced the concentration substantially in the W2B films; however, annealing had no affect on the oxygen concentration in the TiB2 films. The CrB2/SiC interface remained stable during annealing; i.e., Si and carbon were not observed in the boride layers after annealing. In contrast, W2B and TiB2 reacted with the SiC epilayers, and after annealing, Si and carbon were observed at the surface of each boride layer.

Conventional and ionized magnetron sputter‐deposition of nanocrystalline titanium diboride thin films

Titanium diboride has many interesting physical and chemical properties that make it attractive as a tribological coating material. We focus our study on the relationship between hardness, crystal structure and processing parameters for TiB2 thin films produced by conventional and ionized magnetron sputtering. When synthesized by conventional magnetron sputtering, TiB2 films with the highest degree of crystallinity have the highest hardness and are obtainable at an optimum combination of argon pressure and substrate bias. The films also show strong (0001) texture. Such high degree of crystallinity can be obtained without substrate bias by ionized magnetron sputtering, in which enhanced ionization of the plasma is obtained by inductively coupling RF power in the region between the magnetron target and the substrate.

Non-reactively sputtered TiN and TiB2 films: influence of activation energy on film growth

Abstract An unbalanced d.c. magnetron sputtering unit was used to deposit titanium nitride and titanium boride films onto austenitic steel and molybdenum substrates using TiN and TiB 2 targets. An external pair of Helmholtz coils was used to create an uniform axial magnetic field which allowed the ion/atom ratio incident at the growing film to be varied between 0.1 and 1.3. The characterization of the coatings was conducted by scanning electron microscopy, electron probe microanalysis and X-ray diffraction. The aim of this work was to investigate the effects of different activation energies on the film growth and the microstructure of two different hard materials with comparable melting points. The microstructure of the coatings was mainly influenced by the ion bombardment of the substrate, i.e. ion energy and ion intensity. In the case of TiN, single-phase stoichiometric TiN coatings were obtained. The columnar, porous structure of the films occurring at low ion bombardment was changed to a dense structure as the ion energy and the intensity were increased. At the same time the (111) preferred orientation changed to a mixed orientation. The highest hardness values (∼3000 HV0.01) were obtained at intensive ion bombardment. The TiB 2 films exhibited a dense single-phase hexagonal TiB 2 structure with (001) texture which altered to a mixed orientation as the energy of the incident ions was decreased. The Vickers microhardness of the coatings reached values ∼6300 HV0.01.

On the nanocrystalline structure of TiC and TiB2 produced by laser ablation

Abstract Thin films of TiC and TiB2 have been deposited on silicon substrate by pulsed laser deposition technique, under substrate temperatures 25–600 °C. Transmission electron microscopy revealed the nanocrystalline structure of the coatings. The grain size for the TiC film was between 10 and 70 nm and for the TiB2 film was between 10 and 50 nm.

Structure, mechanical and tribological properties of d.c. magnetron sputtered TiB2 and TiB2(N) thin films

TiB2 and TiB2(N) ceramic compounds may have potential application as protective coatings in the magnetic recording industry, because of their high hardness, wear resistance and chemical stability. In this paper, TiB2(N) and TiB2 films were prepared by d.c. magnetron sputtering with and without a nitrogen gas ambient, respectively. The microstructures of these films were examined by X-ray diffractometry and TEM. The mechanical properties of these films were characterized by nano-indentation. Thin film stresses were measured by a wafer curvature technique. The wear volume losses of these films rubbed by a magnetic tape were determined by a sphere-on-flat accelerated wear tester. The results of grazing angle X-ray diffraction and TEM showed that increasing the nitrogen flow rate resulted in a structure change in as-deposited films from (001) textured crystallites to an amorphous microstructure. It was found in nano-indentation and tribological experiments that hardness elastic modulus and wear resistance of these films were significantly improved with an initial incorporation of a small amount of nitrogen. However, further increase of nitrogen resulted in a sharp decrease in these properties in the TiB2(N) films. The mechanical and tribological properties of the TiB2 and TiB2(N) coatings are discussed in terms of the nitrogen content and the film microstructure.

Evaluation of Mechanical Properties of Sputtered Ceramic Films from Nanoindentation and Wafer Curvature Techniques

AbstractTiB2, MoSi2, Si3N4 and Ta4N ceramic films were magnetron sputtered on oxidized Si and Coming 7059 glass substrates at ambient temperature. X-ray diffraction studies indicate that the structure of the films is very different on the two substrates, even though the surface of both substrates is amorphous. The hardness and elastic modulii of the films on oxidized Si are slightly higher than those of the films deposited on Coming glass substrate, even at indentation depths where substrate effects are considered to be negligible. A substantial increase in hardness (5–10 GPa) was observed for TiB2 films, when compared to the properties of bulk stoichiometric TiB2. Stress- temperature diagrams determined from room temperature to 250 C indicate that all the films prepared in this study display a pure elastic behavior in that temperature range.

Aluminum, Titanium Boride, and Nitride Films Sputter-Deposited from Multicomponent Alloy Targets Studied by XPS

X-ray photoelectron spectroscopy (XPS or ESCA), combined with argonion sputter depth profiling, has been employed for the characterization of aluminum, titanium boride, and nitride films deposited by dc-magnetron sputtering from multicomponent alloy targets. The XPS results show that metallic Al, TiB2, and TiN films are formed by this method. However, depth profile results indicated substantial oxide contamination as high as 30 atomic % throughout the bulk of the films. Given the gross oxide contamination, multicomponent alloy target materials appear to be unsuitable for producing high-quality metal/metallic films for applications where electrical conductivity is a critical requirement.

Preparation and characterization of sputtered TiB2 films

Smooth, continuous TiB2 films were deposited on TiB2−AlN composites and Si substrates by sputtering in high vacuum. Excellent adhesion between films and substrates was indicated; no film delamination was induced by Vickers indentation at high loads. Analyses by secondary ion mass and x-ray photoelectron spectroscopies showed that the films were of high purity and contained H, C, O, N, and Na elements as trace impurities. Quantitative depth profile by the elastic recoil detection (ERD) nuclear scattering technique using 30 MeV 35Cl beam revealed that the Ti/B atomic ratio was very close to 0.5 while the 10B/11B isotopic ratio was 0.250.

Structural study of TiB 2 film by grazing incidence X-ray diffraction

X-ray refractive indices of materials are slightly less than unity. Thus, total external reflection occurs at small incidence angles and the component of the electro-magnetic wave entering into the material becomes strongly attenuated 1. Marra e t al. 2 who took notice of this total external reflection phenomenon proposed a new method for structural studies of interface and surface. In this method, intensities are recorded at scattering angles of 20 in directions inclined to the plane formed by the incident beam and the surface normal. Thus, it is sometimes called the surface diffraction method. This surface diffraction has a different geometry from the parallel beam method with a small incidence angle ct on a sample surface and a 20 scan of a detector which is a typical X-ray diffraction technique for structural studies of a thin film supported on a substrate. This conventional method is successfully applicable to a film of, at least, a few hundred nanometers thickness 3. However, Lim e t al. 4 devised a new technique for an investigation of a thinner film by utilizing the total external reflection for the conventional method. A distinctive feature of this method is that the depth profile of atomic structures can be obtained because the X-ray penetration depth changes from several hundred nanometres to a few nanometres by varying the incidence angle ct to the sample surface from below to above the critical angle ~c. In the present study, we used Lim e t al. 's method in order to obtain structural data of a film of titanium diboride (TiB2). Titanium diboride has recently received much attention as a possible new ceramic material by indicating several attractive properties such as higher melting point (about 3000 K), good thermal conductivity, excellent chemical stability and good corrosion resistance 5'6. A TiB2 film grown on a silicon single crystal was prepared by a co-sputter deposition technique with a multiple sputtering apparatus explained in ref. 7. Titanium and boron of 99.9% purity were used as sputtering targets of 76.2 mm in diameter and 3 mm in thickness which were attached to water-cooled backingplates for magnetron sputtering. Sputter deposition was carried out in an argon atmosphere at a pressure of 0.67 Pa after evacuation to 5 x 10 -4 Pa. Titanium and

Preparation of TiB2 films by photochemical vapor deposition using a D2 lamp

TiB2 films have been prepared by photochemical vapor deposition using a D2 lamp from a TiCl4-BCl3-H2-Ar gas mixture. The deposition temperature of the TiB2 films was lowered 50 °C by irradiation with a D2 lamp as compared to that without irradiation. The deposition rate was increased by 1.5–2.5 times with irradiation.

Preparation and Characterization of LPCVD TiB2Thin Films

ABSTRACTTitanium diboride is an interesting new candidate for VLSI interconnection applications due to its high electrical conductivity and its excellent chemical inertness at high temperatures.A thermodynamic analysis of the chemical vapor deposition of TiB2from gaseous mixtures of TiCl4, B2H6and H2onto silicon or SiO2substrates was performed using the SOLGASMIX computer program. Results indicate that at an input gas ratio corresponding to stoichiometry, TiB2should form in the solid phase. For non-stoichiometric input gas mixtures, other solid phases, including oxides and silicides, are expected to result from the reaction with the Si or SiO2substrate. Both the addition of hydrogen to the system and increased deposition temperature are expected to enhance the deposition efficiency of TiB2.Thin films of TiB2, 50 – 120 nm thick, were experimentally deposited on thermally grown SiO2by low pressure CVD using various gas mixtures in the temperature range 400 – 700°C. Depth profiling of the deposited films, using XPS and RBS, indicated the successful growth of a uniform, stoichiometric TiB2film. After deposition, the films were rapid thermal annealed at various temperatures in an effort to reduce their resistivity. Resistivity was reduced by 80 % after an 1150°C, 10 sec RTA in Ar to a value as low as 40μΩ-cm, only 4 times larger than that reported for hot pressed polycrystalline TiB2. X-ray diffraction of as-deposited samples showed no crystalline peaks; however, annealed films exhibited the expected TiB2peaks as well as those of Ti3O5and TiO2. The titanium oxide was most likely produced during annealing due to trace amounts of oxygen in the Ar atmosphere. The average grain size measured 0.1μm via TEM. More careful control of growth and annealing conditions is expected to result in even lower resistivity TiB2films.

The Mechanical Properties of Cu/TiB2 Multilayer Structures

ABSTRACTWe have investigated the hardness and tribological properties of Cu/TiB2 multilayer structures deposited on substrates of tempered martensitic steel. Films of Cu and TiB2 were also deposited as hardness standards. The wear properties of the films were found to be poor, because of lack of adhesion. However, the films do appear to have good fracture toughness. The hardness of the multilayer was 18% greater than that predicted by the law of mixtures applied to the reference standards and, when corrected for variations in substrate hardness, very nearly equal to that of the TiB2 film. Irradiation by 400 keY Ne-ions to doses of 1.0, 6.0, and 12×1015 ion/cm2 results in a slight hardening of the multilayer. The structure was found to have excellent stability against radiation damage.

イオンプレーティングによるＴｉＢ２編の作製

イオンプレーティングによるＴｉＢ２編の作製

ChemInform Abstract: Titanium, Zirconium, and Hafnium Tetrahydroborates as “Tailored” CVD Precursors for Metal Diboride Thin Films.

AbstractAn extension of a chemical vapor deposition (CVD) approach (published earlier) to the preparation of thin films of TiB2, ZrB2 and HfB2 at exceptionally low temp. (200 °C) and low pressure (10‐4 torr) from precursor compounds such as (I) is described.

遷移金属非酸化物の材料開発

The preparations (thin film, whisker, fine powder, sintered body and single crystal) of transition metal carbides, nitrides and diborides, electrical, superconductive, mechanical and oxidation resistance characteristics, and practical applications of these compounds are reviewed from the standpoints of material science. These refractory compounds are promising candidate materials for the following areas.(1) Super-LSI technology and electronic device: field and thermal emitters, TiN as diffusion barrier in metallization to Si semiconductor, resistive thermoconductive humidity sensor with TaN film and Josephson turnel junction with NbN film.(2) Energy related materials: solar-selective surface with ZrC thin film, emitter for thermionic generator, electrodes (ZrB2 and HfB2) for MHD generator and first wall coated with TiC or TiB2 film for tokamak.