Thick Ti Films Research Articles

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness approximatly 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm2 to 1.0 x 10(17) ions/cm2 The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TIN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

The role of Mg 2Si formation in the hydrogenation of Mg film and Mg nanoblade array on Si substrates

In this paper, both an Mg film and an Mg nanoblade array have been first fabricated directly on Si substrates and hydrogenated under 20 bar hydrogen pressure at temperatures ranging from 200 °C to 350 °C. It is found that Mg 2Si alloy starts to form at T = 200 °C in both the Mg samples, which produces a two-layered structure in the hydrogenated films with the bottom dense layer of Mg 2Si. To prevent Mg alloying with Si, a layer of 200 nm thick Ti film was deposited in between the Mg samples and Si substrates as a diffusion barrier, and their hydrogenation results show that Mg 2Si formation is suppressed greatly and even eliminated in nanoblades, though Mg 2Si hillock defects are observed in the hydrogenated films, which could be formed progressively through the pinholes in the Ti film. To improve the diffusion barrier, a unique structure, consisting of layers of Ti nanorod array and Ti film, has been designed for Mg-based nanostructure deposition. The hydrogen cycling study demonstrates that the structure of 450 nm Ti nanorods on 1 μm Ti film can endure enough number of cycles for the hydrogen storage kinetic and thermodynamic study of film-based Mg nanostructures with/without nanocatalyst, and thus one can gain a fundamental understanding of hydrogen interacting with Mg intrinsic nanostructures and nanocatalysts.

Anodic bonding of glasses with interlayers for fully transparent device applications

Thermal processing parameters of vacuum deposited titanium thin films are determined for anodic bonding of glass plates with interlayers for fully transparent device applications. Vacuum thin film deposition and sealing conditions strongly influence the quality of the bonds. 10 −4 hPa and 10 −5 hPa vacuum of 40 nm and 80 nm thick Ti film deposition and 20 min preheating time, 420–530 °C temperature, 0.5–5 min bonding time and 50–200 V voltage were applied during seal fabrication. Both optical transmittance and electrical resistivity of the interlayers were found to increase with higher bonding temperature and voltage due to higher degree of Ti thin film oxidation. The optimal conditions for transparent and conductive interlayer fabrication were determined and seals of 25 MPa tensile strength were manufactured. Titanium thin films have not been reported to be processed for fully transparent device applications so far.

The effect of thickness on the properties of titanium films deposited by dc magnetron sputtering

Titanium (Ti) films of thickness in the range of 101–254 nm were prepared onto glass and silicon substrates by direct current magnetron sputtering method. The effect of thickness on the electrical, structural, optical and surface properties of the films was studied. The room temperature sheet resistance decreased from 14.3 to 3.6 Ω/□ and the temperature coefficient of resistance value increased from 0.14 to 0.20% K −1 with increase in the thickness of the film. The optical and surface composition characteristics of the films were least influenced by the thickness. The films of all thickness exhibited hexagonal closed packed crystalline structure with predominant (0 0 2) crystallite orientation and an additional (1 0 0) orientation particularly in the films of thickness in the range of 153–205 nm. The average particle size in the films varied from 9 to 40 nm with the thickness.

Chemical Interactions Between Cement and E‐Glass Fibers with a CaO–BaO–SiO2–TiO2 Coating

E‐glass fibers were coated with a 15CaO–15BaO–20SiO2–50TiO2 thin film by the sol–gel method. Mechanical and chemical tests were performed on coated and uncoated fibers in cement and cement extract solutions to investigate the interactions between cement and gel‐glass film. The results show that the resistance of E‐glass fibers to the alkali cement medium is enhanced by the 15CaO–15BaO–20SiO2–50TiO2 coating. The significant roles of TiO2, CaO, and BaO in the protection fibers from the alkaline attack of cement are described. Some evidence is presented that the alkali corrosion of the coated fibers results in the formation of a thick and compact Ti film that suppresses further corrosion reaction.

Microstructure of brazed joints between mechanically metallized Si3N4 and stainless steel

Brazing has been increasingly used to join metals to advanced ceramics. Brazing covalent materials requires either the use of active filler alloys or the previous metallization of the surface. To that end, a new and simple mechanical technique has been applied to metallize advanced ceramics, thus avoiding the use of costly Ti-based active filler alloys. The mechanical metallization of Si3N4 with Ti was employed as an alternative route to deposit active metallic films prior to brazing with stainless steel using 72% Ag--28% Cu or 82% Au—18% Ni eutectic alloys. The brazing temperatures were set to 40°C or 75°C above the eutectic temperature of each filler alloy. Ti-films of average thickness 4 μm produced adequate spreading of both filler alloys onto Si3N4 substrates, which were subsequently brazed to stainless steel. The interface of Si3N4/310 stainless steel basically consisted of a reaction layer, a precipitation zone and an eutectic microconstituent. Mechanically sound and vacuum-tight joints were obtained, especially upon brazing at relatively lower temperatures. Increasing the brazing temperature resulted in thermal cracking of the Si3N4, possibly due to increased thermal stress.

Target surface oxide layer formed by reactive sputtering of Ti target in Ar+O2 mixed gas

Reactive sputtering is one of the most widely used techniques for preparing compound thin films. In this study, a Ti model target, a 1μm thick Ti film sputter deposited on a Si wafer, was used as the sputtering target. The thickness of the oxide layer formed on the surface of the model target after sputtering in an Ar+O2 mixed gas atmosphere was measured by ellipsometry under various varying processing parameters including oxygen flow ratio, sputtering time, rf power, and total gas pressure. The oxide layer thickness was varied from a few nanometers to approximately 100nm by changing the parameters, and a nonuniform oxide layer thickness was observed on the target surface.

Method to detect the property of complex oxide structure formed by AFM anodic oxidation completely

Thin titanium film (3∼8 nm thick) can be oxidized completely with atomic force microscope anodic oxidation to form a metal–insulator–metal structure to fabricate various nanodevices. Whether the Ti film is oxidized down to the bottom is vital to the nanodevices. We have fabricated a delicate Ti oxide structure of two triangles on about 3 nm thick Ti film. The theoretical calculation of the ratio of h ox / d Ti = 0.58 indicates the Ti film has been oxidized completely.

Texture and sheet resistance of Al alloy thin films on Ti and TiN thin films

Ti films prepared by ionized physical vapor deposition (I-PVD) and TiN films prepared by metalorganic chemical vapor deposition (MOCVD) were examined as the underlayers of the Al interconnect films. The crystallographic texture of the Al films and the sheet resistance of the thin-film stacks were investigated at various thicknesses of the Ti or TiN thin film. The sheet resistance of the thin-film stacks was also measured after annealing at 400 °C in an N2 ambient. For the I-PVD Ti underlayer, the excellent texture of the Al (1 1 1) was obtained even on a 5-nm thick Ti film. However, the sheet resistance of the multilayer structure increased after the annealing due to the reaction between Al and Ti. MOCVD TiN layers between the Ti film and the Al film could suppress the Al–Ti reaction without severe degradation of the Al (1 1 1) texture. Excellent texture of the Al film was obtained with thin MOCVD TiN films below 5 nm.

Structural and chemical properties of ac(2×2)−Ti/Pt(100)second-layer alloy: A probe of strong ligand effects on surface Pt atoms

We investigated the structure and chemisorption properties of a Ti/Pt(100) surface alloy using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD), low-energy alkali ion scattering (ALISS), and temperature programed desorption (TPD). Samples were prepared by evaporating Ti onto a clean hex-Pt(100) reconstructed surface at 300 K. After annealing the sample to 800 K, a $c(2\ifmmode\times\else\texttimes\fi{}2)$ LEED pattern was observed that sharpened as the temperature was increased to 920 K. Further annealing to 1000 K caused this $(2\ifmmode\times\else\texttimes\fi{}2)$ LEED pattern to become diffuse because of the onset of disorder in the surface layers resulting from Ti diffusion into the bulk. Using XPD and ALISS, we determined that this LEED pattern is due to an ordered alloy structure that has Ti atoms present in the second layer of a $c(2\ifmmode\times\else\texttimes\fi{}2)\ensuremath{-}\mathrm{T}\mathrm{i}/\mathrm{P}\mathrm{t}(100)$ surface alloy, and not in the topmost layer. Thus, the surface layer of this alloy is pure Pt. XPS showed that the Ti $2p$ peak from the surface alloy is shifted by 1.4 eV to higher binding energy than that of a thick Ti film, and the Pt $4f$ peak is shifted by 0.1 eV higher from that of the clean hex-Pt(100) reconstructed surface, consistent with the formation of strong intermetallic bonds upon alloying. The chemisorption properties of the surface alloy were probed using CO and ${\mathrm{H}}_{2}$ adsorption. CO adsorbed reversibly on the alloy, desorbing in TPD in a broad peak with a maximum at 376 K. This is lower by 132 K from the CO desorption peak from a clean Pt(100) surface. Thermal desorption of ${\mathrm{H}}_{2}$ showed a similar peak shift to lower temperature, and much less hydrogen (20%) adsorbed on the $c(2\ifmmode\times\else\texttimes\fi{}2)\ensuremath{-}\mathrm{T}\mathrm{i}/\mathrm{P}\mathrm{t}(100)$ alloy than on Pt(100). These results show that second layer Ti atoms exert a strong ``ligand'' or electronic effect on Pt atoms at the surface. Thus, the $c(2\ifmmode\times\else\texttimes\fi{}2)\ensuremath{-}\mathrm{T}\mathrm{i}/\mathrm{P}\mathrm{t}(100)$ surface alloy represents an interesting model system for studying ligand effects on the chemistry of a bimetallic alloy surface.

One-dimensional analytical model for oxide thin film growth on Ti metal layers during laser heating in air

This paper presents the theoretical and experimental results for oxide thin film growth on titanium films previously deposited over glass substrate. Ti films of thickness 0.1μm were heated by Nd:YAG laser pulses in air. The oxide tracks were created by moving the samples with a constant speed of 2mm/s, under the laser action. The micro-topographic analysis of the tracks was performed by a microprofiler. The results taken along a straight line perpendicular to the track axis revealed a Gaussian profile that closely matches the laser’s spatial mode profile, indicating the effectiveness of the surface temperature gradient on the film’s growth process. The sample’s micro-Raman spectra showed two strong bands at 447 and 612cm−1 associated with the TiO2 structure. This is a strong indication that thermo-oxidation reactions took place at the Ti film surface that reached an estimated temperature of 1160K just due to the action of the first pulse. The results obtained from the numerical integration of the analytical equation which describes the oxidation rate (Wagner equation) are in agreement with the experimental data for film thickness in the high laser intensity region. This shows the partial accuracy of the one-dimensional model adopted for describing the film growth rate.

Structure of Ti films deposited on MgO(001) substrates

The growth and structure of Ti thin films deposited by electron beam evaporation at 273 K in a vacuum of about 10 −7 Pa on MgO(001) have been studied by means of transmission electron microscopy. It is found that a thin layer, whose thickness is up to about 4 nm, is fcc (or tetragonal) structure. When the thickness increases to more than about 6 nm, the structure gradually changes to an hcp structure with two different orientations: one is (00.1) hcpTi//(001) fccTi//(001) MgO, and the other is (03.5) hcpTi//(001) fccTi. The electron diffraction patterns from 60 nm thick Ti film also show reflection spots at {110} points on fcc Ti reciprocal plane, which show metastable γ-hydride precipitation takes place in the layer. The orientation relationships and growth mechanism of the epitaxial Ti films on MgO(001) are discussed using molecular dynamics simulations performed by Hara et al. for MBE growth of a Lennard-Jones system.

Structure of α-Al2O3(0001) surface and Ti deposited on α-Al2O3(0001) substrate: CAICISS and RHEED study

The structure of the α-Al2O3(0001) surface and Ti deposited on the α-Al2O3(0001) substrate has been investigated using co-axial impact collision ion scattering spectroscopy and reflection high energy electron diffraction. It has been found that the Al2O3 (0001) surface is terminated by an Al layer, as predicted by several theories. The coexistence of Al and O terminated domains has not been observed. In the thickness range of the overlayer Ti films from 4 to 40monolayers on Al2O3 (0001), the growth mechanism of the deposited films has been revealed to be consistent. The structure of a thick Ti film formed epitaxially on the substrate corresponds to α-Ti, while in the initial stage the adsorbed Ti atoms are thought to succeed to the periodicity of the Al2O3 (0001) surface.

Influence of MgO(1 0 0) substrate surfaces on epitaxial growth of Ti films

Abstract The growth of Ti films prepared on MgO(1 0 0) substrates by an electron-beam heating method has been studied using transmission electron microscopy. The 10 nm thick Ti films deposited on as air-cleaved chemically-polished MgO(1 0 0) substrates without heat treatment showed fcc electron diffraction spots due to TiHx crystallites (x ≒ 1.5) with NaCl structure and TiOy crystallites (y ≒ 1.0) with CaF2 structure, which were formed by compound layer containing H and O atoms, in addition to hcp Ti rings. When a 50 nm thick Ti was deposited at room temperature (RT) on chemically-polished MgO(1 0 0) substrates with heat treatment at 900°C for 30 min, hcp Ti crystallites with only (1 0 · 1) orientation were formed. The Ti films heat treated at 800°C for 30 min in vacuum after being deposited at RT indicated the existence of discrete and fully oriented hcp Ti crystallites. On the other hand, when a 50 nm thick Ti was deposited at RT on as air-cleaved ones without heat treatment, hcp Ti crystallites with only (0 0 · 1) orientation grew on most of the surface. This result shows that the epitaxial growth of Ti film is not necessarily inhibited by the exposure of MgO substrate surface to atmosphere, and that such surface is very effective for the growth of epitaxial films with preferred orientations.

Growth and structure of Ti films deposited on chemically polished MgO(100) substrates

The growth and structure of Ti films deposited at various temperatures in vacuum of about 10 −6 Pa on chemically polished MgO(100) substrates with heat treatment at 900°C for 30 min and without heat treatment have been studied by means of transmission electron microscopy. It is found that the thin layer, whose thickness is up to about 5 nm, is composed of fcc TiH x and TiO y crystallites at an early stage of deposition. The growth of hcp Ti crystallites becomes dominant when the substrate temperature is raised to above 800°C. The 50 nm thick Ti films heated at 800°C for 30 min immediately after being deposited at room temperature are found to be far better defined epitaxial films with only (10·1) orientation than those deposited at 800°C. The 50 nm thick Ti films deposited at room temperature on as chemically polished MgO(100) substrates without heat treatment change from amorphous to epitaxially grown ones with (10·1) orientation when heated at temperatures above 800°C for 30 min in vacuum. This shows that the heating of Ti films deposited at room temperature on as chemically polished MgO (100) substrates without heat treatment is more effective for the epitaxial growth.

Lateral self-limitation in the laser-induced oxidation of ultrathin metal films

cw-laser-induced local oxidation of ultrathin (3–60 nm) titanium films on glass in air is studied. It is shown, that the brightening of the films upon through-oxidation forms a negative feedback to this highly nonlinear process. It offers the possibility of stable writing of oxide line structures narrower than the diffraction limited focused laser spot. The optimum metal film thickness is of the order of the light absorption length in the metal. Transparent isolated oxide lines and gratings with periods down to 250 nm and line width down to 165 nm were recorded in 6–15 nm thick Ti films on glass by using the radiation of the Ar ion laser (λ=488, 514 nm).

Epitaxy of titanium nitride thin films grown by nitrogen implantation

Nitrogen ions (N 2 +) with energy 62 keV were implanted into 100 nm thick Ti films evaporated onto thermally cleaned NaCl substrates. Unimplanted and N-implanted Ti films were examined by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. It was revealed that N-implantation expands the h.c.p. Ti lattice and reduces the hydrogen concentration in the evaporated Ti film. The former induces the h.c.p.-f.c.c. transformation and then leads to the growth of (001) oriented TiN y by occupation of the octahedral sites in the f.c.c. Ti sublattice by N. The latter indicates the escape of H from TiH x, and leads to the growth of (110) oriented TiN y, by the similar occupation by N.

Suppression of the Phase Transition to C54 TiSi2 due to Epitaxial Growth of C49 TiSi2 on Si(001) Substrates in Silicidation Process

The epitaxial C49 TiSi2 formed after annealing of Ti films deposited on Si(001) substrates has been studied by grazing-incidence X-ray diffraction. The relations C49 TiSi2(10\\bar1)∥Si(001), C49 TiSi2(100)∥Si(001), and C49 TiSi2(010)∥Si(001) are observed on a highly BF2-implanted substrate, and the a or b face of C49 is sharply orientated toward the directions deviating ±5° from Si<110> on a clean substrate in ultrahigh vacuum (UHV). These epitaxial C49 grains are thermally stable and difficult to transform into the C54 phase even after annealing at high temperature. In contrast, ramdomly distributed C49 grains have been observed on unimplanted and low-dosed substrates and for thick Ti films in UHV. These polycrystalline C49 grains are thermally unstable and easily transformed into the C54 phase. The influence of implantation and UHV process on the growth of the epitaxial C49 and the phase transition of C49 to C54 are discussed.

表面改質による窒化アルミニウムと金属の接合 （第１報） Ｔｉ＋Ｃｕ二層メタライズしたＡｌＮとＣｕのはんだ付

Soldering of surface-modified AIN to copper was investigated using Sn-38 mass%Pb solder. AlN substrate was dually metallized by Ti and Cu using ion plating technique as follows ; the 10μm thick Ti film was first plated on the AIN substrate, heat-treated in vacuum on various conditions and then the 5-10μm thick Cu film was plated on the heat-treated Ti film again. The thermal stress and heat conduction analyses suggested that the soldered joints could possess the superior properties when the thickness of soldering layer was kept less than 0.4 mm. Defects such as micro voids and cracks were occurred in Ti film after heat treatment, and the fraction of defects increased with increasing the treating temperature and time. The tensile strength of Ti+Cu dual metallized AlN to copper joint was approx. 20 MPa, and slightly decreased as the treating time of Ti film was increased. The Ti+Cu dual metallized AIN to copper soldered joint indicated the superior reliability for thermal fatigue and heat conduction.

The Influence of RTA Heating Rate on the TiSi2 and Si - TiSi2 Interface Roughness

ABSTRACTIn TiSi2 metallized devices, the second distribution of leakage current (I&gt;lμA) is caused by the Si/TiSi2 interface roughness. In this work, 40gm thick Ti films are sputtered onto Si waters. RTA was done in N2 atmosphere. Heating rates of 0, 0.5, 1, 5, and 100°C S−-1 are examined. Samples are characterized by AFM, RBS, XRD and laser light scattering methods. The parameters related to roughness are heating rate sensitivity and oxygen contamination which decreases the roughness on the interface.