Dense TiN Research Articles

Characterization of out-of-band radiation and plasma parameters in laser-produced Sn plasmas for extreme ultraviolet lithography light sources

Out-of-band (OOB) radiation, in contrast to the in-band radiation at 13.5 nm in a 2% bandwidth, emitted from dense tin plasmas generated by a laser was investigated for application as an extreme ultraviolet lithography light source. It was found that the continuum spectrum, which overwhelms the atomic and ionic line emissions, is responsible for the intense OOB radiation. The spectral distribution of the continuum emission matches that of blackbody radiation with a temperature of about 10 eV. The OOB radiation can be considerably suppressed by employing a minimum-mass target and short-pulse laser irradiation. Spectroscopic observations were made to examine the spatiotemporal behavior of the plasma immediately after laser irradiation. Prominent line broadening due to the Stark effect in the high-density plasma was observed, from which the variation of the electron density was deduced. The electron density and temperature on the target surface were 1017–1018 cm−3 and a few eV’s, respectively, in the first 200 ns after laser illumination. In addition, the expansion velocities of neutral and singly ionized tin atoms were deduced from time-of-flight transients in the spectral emission.

Effects of continuously applied stress on tin whisker growth

A simple four-point bending technique in conjunction with scanning electron microscopy (SEM) was employed to investigate the relationship between continuously applied mechanical stress and tin whisker growth on bright tin-plated copper specimens at room temperature. Measurements of whisker length and density were periodically taken for each specimen during a 7-month exposure to applied stress. Tin whiskers were found on the tin-plated specimens with or without the presence of mechanically applied stresses. A continuously applied compressive stress resulted in formation of longer and more dense tin whiskers, in comparison with the cases of no applied stress and applied tensile stress. However, an increase in the applied compressive stress level caused an increase in the whisker density but a decrease in the whisker length. On the other hand, a continuously applied tensile stress was found to reduce both the whisker density and length, compared to the case of no applied stress. Apparently, application of a continuous tensile stress could provide an effective means in retarding tin whisker growth.

Investigation of Electron Traps in SnO<sub>2</sub> Based Varistor Ceramics

Dense tin oxide based ceramics are a new type of varistor materials. To further understand the electrical properties of SnO2 varistors doped with CoO, Nb2O5, and Cr2O3, the techniques of capacitancevoltage (C-V) measurement and deep level transient spectroscopy (DLTS) were used to investigate the electron traps in the SCN samples (doped with 1.0 mol% CoO and 0.05mol% Nb2O5) and SCNCr samples (doped with 1.0 mol% CoO, 0.05mol% Nb2O5 and 0.05mol% Cr2O3). Two electron traps were detected: trap T1 is located at Ec - 0.30 ± 0.01eV and trap T2 is located at Ec – 0.69 ± 0.03eV for both SCN and SCNCr samples. The variations in the donor density and trap density could be related to the addition of chromium oxide. The features of these traps are discussed based on the defect theory related to the SnO2 varistors.

Defect formation of chemical-vapor deposited tungsten on rapid thermal-annealed TiN/Ti

Defect formation during W chemical-vapor deposition on TiN/Ti is studied using a variety of TiN/Ti annealing and TiN deposition conditions. Most of the defects observed on the W surfaces are associated with a great change of TiN film stress toward tensile direction after the rapid thermal annealing. Dense TiN (sputtered at a chamber pressure of 5.1 mTorr) produces a stress change of the TiN/Ti stack from − 0.52 × 10 9 to 2 × 10 9 Pa, while porous TiN (sputtered at a chamber pressure of 12.8 mTorr) produces a stress change from − 0.11 × 10 9 to 0.95 × 10 9 Pa. When the porous TiN is used for the diffusion barrier, defect counts on the W films are minimized (< 100 ea. per wafer) and even comparable with those of the W films on unannealed TiN/Ti. Microcracks or pinholes caused by a huge stress change of the TiN provide a pathway for WF 6 reaction with underlying Ti and forming the titanium fluoride, such as TiF 3 and TiF 4. Large stress developed due to volume expansion during fluorination of the Ti layer results in local delamination or abnormal growth at the W/Ti and the Ti/SiO 2 interfaces.

An investigation of the electrochemical properties of PVD TiN-coated SS410 in simulated PEM fuel cell environments

Bipolar plates are a key component of PEM fuel cells, and they constitute a large portion of the weight and total cost of a fuel cell stack. In order to reduce both the cost and weight of the bipolar plates, considerable attention is being paid to developing metallic bipolar plates to replace non-porous graphite. In this study, TiN was coated on a martensitic stainless steel (SS410) using a PVD technology (plasma enhanced reactive evaporation) to increase the corrosion resistance of the base metal. XRD, SEM, EIS and potentiodynamic tests were used to characterize the TiN-coated SS410. In order to investigate the suitability of these coated materials as the anodes and cathodes in a PEMFC, potentiostatic tests were conducted under both simulated cathode and anode conditions. The simulated anode environment was - 0.1 V vs SCE purged with H 2 and the simulated cathode environment was 0.6 V vs SCE purged with O 2 . The dense TiN coatings formed on SS410 much improved the corrosion resistance of SS410 and, thus, these coated materials could potentially be used in PEMFCs as a bipolar plate material provided they also satisfy the other physical and mechanical property requirements such as interfacial contact resistance, light weight, high mechanical strength and manufacturability.

Consolidation of Nano‐Sized TiN Powders by Spark Plasma Sintering

Nano‐sized TiN powders with an average particle size of 19 nm were synthesized via a new method, reduction–nitridation reaction in liquid ammonia. A consolidation procedure using spark plasma sintering (SPS) was used, and a dense TiN ceramic (&gt;98% of theoretical) with mean grain size of 100–150 nm was obtained at 1380°C. The influence of sintering temperature on grain growth and microstructural evolution was also discussed.

Nonlinear Electrical Characteristics of Antimony and CopperDoped Tin Oxide Based Varistor Ceramics

The novel CuO-doped dense tin oxide varistor ceramics are investigated.The densification of tin oxide varistor ceramics could be greatlyimproved by doping copper oxide additives. The introduction of antimonyadditives into a SnO2.CuO ceramic system would make it possessexcellent nonlinearity. The sample doped with 0.05 mol%Sb2O3 possesses the highest nonlinearity coefficient(α = 17.9) and the lowest leakage current density (JL = 52 μAcm−2) among all the samples. A modified defect barrier model isintroduced to explain the formation of the grain-boundary barrier. Thenonlinear behaviour of (Cu, Sb)-doped SnO2 varistor system couldbe explained by the barrier model.

Spectral control of emissions from tin doped targets for extreme ultraviolet lithography

We have investigated the unresolved transition array (UTA) emission around 13.5 nm from solid density tin and tin doped foam targets. Extreme ultraviolet (EUV) spectral measurements were made in the wavelength region 11–17 nm using a transmission grating spectrograph and the EUV in-band conversion efficiency was measured using an absolutely calibrated EUV calorimeter. The aim of this work was to optimize the UTA emission with the proper density of tin dopant in low-Z foam targets. The addition of tin as an impurity leads to a reduction in the plasma continuum and narrowing of the UTA compared with fully dense tin targets. Our studies indicate that the required percentage of tin for obtaining bright in-band spectral emission is less than 1%.

Formation by reactive magnetron sputtering of TiN coating on Ti-implanted magnesium alloy

Reactive magnetron sputtering method was used to deposit TiN coating on Ti-implanted magnesium alloy. FESEM, GIXRD and AES were used to investigate this surface system's micro-morphology, crystalline structure and chemical composition, respectively. It showed that TiN coating took on a compact surface morphology and existed as a columnar crystalline structure. The results of the electrochemical test and immersion test showed that the corrosion resistance of AZ31 was greatly improved in 3.5 wt.% NaCl solution by this kind of surface treatment technique. It was mainly due to the combined effect of the dense TiN coating, the Ti-implanted layer and the good adhesion between coating and substrate.

Autocatalytic tin plating in the fabrication of tin-coated copper tube

Tin-coated copper tubes are water service tubes, which combine good properties of tin and copper, showing, for example, superior corrosion resistance in aggressive waters as compared to conventional copper tubes. Tin coatings are generally deposited by an immersion method, which introduces rather thin coatings. Autocatalytic tin coatings are capable of increasing thickness of the existing tin coatings and, therefore, of improving their properties. The present study reports fabrication of tin-coated copper tubes by a two-step coating process, which is composed of immersion tin-plating phase combined with an autocatalytic plating step, utilising a bath containing sodium hydroxide, sodium citrate and stannous chloride. Development of the coatings proceeds by alternate grain nucleation and growth processes; grain growth advances until a completely compact layer of tin grains is formed, which is followed by a new nucleation and successive growth phase. Bath temperature of 80 °C was found to be optimal for the autocatalytic tin coating development; here, grain growth is favoured, introducing an even coating layer with a reasonable thickness. Below 80 °C, discontinuities may be introduced to coating structure due to an excessive coating nucleation over a grain growth process. Above 85 °C, in turn, the reaction to deposit the coating starts to be uncontrollable, resulting in an unstable plating bath. 90 min plating time was found optimal to reach a reasonable coating thickness and avoid secondary nucleation processes, which may yield surface irregularities in the coating. Utilisation of the autocatalytic coatings yields improved corrosion performance in tin-coated copper tubes due to a more efficient shielding ability. Studied by potentiodynamic polarisation experiments in water showing moderate aggressivity to copper, utilisation of dense and continuous autocatalytic tin coatings was observed to shift corrosion current density value of an uncoated copper to less than one tenth of the original value and corrosion potential of copper by up to 350 mV in negative direction, which is much more significant than an influence caused by immersion tin coatings. Besides, the autocatalytic coatings of the present study show lower corrosion potential values than tin-coated copper tubes reported so far, which means an enhanced cathodic protection to copper.

Metal ion release from TiN coated CoCrMo orthopedic implant material

In this study, a medical grade CoCrMo alloy was coated with TiN by means of physical vapor deposition (PVD) technique at 550 °C for 6 h. The TiN layer microstructure and thickness were studied by X-ray diffraction (XRD) and cross-sectional scanning electron microscopy (SEM). The adhesive strength of the TiN coatings on the CoCrMo substrate was studied by a commercially available Scanning Scratch Tester. Static immersion test was conducted to investigate the effectiveness of TiN coating in preventing the dissolution of metal ions into the simulated body fluid (SBF) from the substrate by atomic absorption spectrometry (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The XRD results showed that the PVD coated TiN films exhibited (111) preferred orientation, while the SEM analysis indicated quite uniform and highly dense TiN coated layer (about 3 μm thick) with a columnar growth mode reaching from substrate to coating surface. The scratch test results showed that the adhesive strength between the TiN film and the CoCrMo substrate was adequate. The AAS and ICP-OES results showed that the presence of the TiN coating prevented the release of cobalt and chromium metal ions from the substrate CoCrMo alloy whereas cobalt was preferentially dissolved from the as-polished material. Calcium phosphate precipitation was observed on the surface of the as-polished material, indicating a degree of bioactivity of the as-polished surface which is absent in the TiN coated substrate alloy.

Deposition of TiN thin films using grid-assisting magnetron sputtering

This paper presents a modification to conventional magnetron sputtering systems. The introduction of grid in front of the target increases metal ion ratio. By using optical emission spectroscopy (OES) and observing both Ti neutrals and Ti ions, the relative fraction of ion could be qualitatively extended to grid-attached magnetron sputtering as compared with the conventional magnetron system. And, experimental results clearly demonstrated that a smooth and dense TiN film with a specular reflecting surface and could be produced by grid-attached magnetron with much increased Ti ion fractions as compared to conventional magnetron. From the potentiodynamic polarization test, it was shown that the corrosion current density of TiN deposited by two grid-attached magnetron sputtering was lower than that of TiN deposited by conventional magnetron sputtering.

Ion deposition in a crossed E× B field system with vacuum arc plasma sources

The system with crossed magnetic and electric fields and vacuum arc plasma sources for ion deposition and low-voltage plasma treatment and plasma immersion ion implantation has been investigated. The use of crossed E× B fields provides intense gas ionization and suppresses sheath expansion. Maximum deposition rate of about 1 μm min −1 was obtained on the target surface located under the area where intense ionization of reactive gas occurs (circular area of about 40 mm wide around the target). Without magnetic field the maximum rate of only 0.15 μm min −1 can be achieved. In the crossed E× B fields, high-quality dense TiN coating was obtained. High ion current density to the target surface reaches 500 A m −2, provides effective cleaning of the target surface and heating of the growing film. The ratio of metal plasma current and reactive gas ion current reaches 2.1 and can be easily changed by adjusting the magnetic field strength, without changing the vacuum arc gun current. The uniform film deposition around circumference of the target is provided as a result of ion magnetization in the crossed field zone. The uniform film deposition along the entire target length can be provided by moving magnetic field up and down.

Minimizing segregation during the controlled directional solidification of dendritic alloys

Gravity-driven convection induced in the liquid by density gradients of temperature or composition disrupts uniform dendritic growth during controlled directional solidification and promotes severe macrosegregation. The solute-rich region about the dendrite tip appears to play a pivotal role in channel initiation. Allen and Hunt referred to this region as an "initial transient" or dynamic region constituting steep concentration gradients. Experimental investigation also point to the role the tip region plays in developing microstructure. Hellawell and co-workers showed that flow-through dendritic channels could be effectively disrupted, and segregation minimized, during the gradient freezing of bulk castings by rotating the melt through a slight angle with respect to Earth's gravity vector. Adapting this principle to controlled directional solidification, it has been shown" that segregation in dendritic alloys can be minimized, and properties improved, by processing the sample near horizontal in conjunction with a slow axial rotation of the crucible. It is postulated that the observed microstructural uniformity arises by maintaining the developing solute field about the dendrite tip. Solute rejected during vertical directional solidification will rise or sink parallel to the primary dendrite arms during axial rotation setting the stage for accumulation, instabilities, and segregation. In contrast, during horizontal growth, the rejected solute will sink or rise perpendicular to the primary dendrite. Now, in the presence of a slight axial rotation, solute that was initially sinking (or rising) will find itself above (or below) its parent dendrite, i.e., still about the tip region. The following is intended to experimentally demonstrate the viability of this concept in coordination with a model that gives predictive insight regarding solute distribution about growing dendrites. Alloys based on the lead-tin eutectic system were used in this study. The system is well characterized, the constituent metals are available in a very pure form, and the thermophysical properties are well known. During solidification of hypoeutectic alloys, e.g., 55 wt pct Pb, the primary dendrites reject the less dense tin, and for the hypereutectic alloys, e.g., 75 wt pct Sn, the primary dendrites reject denser lead. Alloys were prepared by melting appropriate amounts of lead and tin in a glass crucible after which the homogeneous liquid was sucked directly into 5-mm i.d. glass tubes. The sample tube, containing approximately 30 cm of alloy, was then mechanically driven into the directional solidification furnace assembly and positioned such that approx. 20 cm of the sample was remelted. Subsequently, directional solidification was initiated by withdrawing the sample through a water-cooled jacket at a constant growth velocity of 2 ,microns/s. After 5 to 6 cm of growth, the sample was quickly removed from the furnace and quenched in a water bath to preserve the solid-liquid interface. Samples were directionally solidified vertically upward, nearly horizontally, and some in conjunction with an applied axial rotation of the crucible. Temperature gradients at the solid-liquid interface were measured with an in-siru K-type thermocouple. Solidified samples were cut perpendicular and parallel to the growth direction and conventionally prepared for microscopic examination.

Temperature dependence of inductively coupled plasma assisted growth of TiN thin films

Abstract The use of low pressure high density plasmas to assist the synthesis of ceramic thin film materials is in its infancy. Using an inductively coupled plasma assisted magnetron sputtering system, we examine the dependence of plasma-assisted growth of TiN thin films on growth temperature at different ratios of ion flux to neutral atom flux. Our results indicate that a temperature independent densification of TiN films occurs above a certain ion to neutral atom flux ratio. As an example of this temperature independent densification, we demonstrate the formation of dense B1 TiN crystalline thin films at growth temperatures down to ∼100 K.

Dense fully 111-textured TiN diffusion barriers: Enhanced lifetime through microstructure control during layer growth

Low-temperature deposition of TiN by reactive evaporation or sputter deposition onto amorphous substrates leads to highly underdense layers which develop mixed 111/002 orientations through competitive growth. In contrast, we demonstrate here the growth of low-temperature (450 °C) fully dense polycrystalline TiN layers with complete 111 texture. This was achieved by reactive magnetron sputter deposition using a combination of: (1) highly oriented 25-nm-thick 0002 Ti underlayers to provide 111 TiN orientation through texture inheritance (local epitaxy) and (2) high flux (JN2+/JTi=14), low-energy (EN2+≃20 eV), N2+ ion irradiation in a magnetically unbalanced mode to provide enhanced adatom diffusion leading to densification during TiN deposition. The Ti underlayers were also grown in a magnetically unbalanced mode, in this case with an incident Ar+/Ti flux ratio of 2 and EAr+≃11 eV. All TiN films were slightly overstoichiometric with a N/Ti ratio of 1.02±0.03. In order to assess the diffusion-barrier properties of dense 111-textured TiN, Al overlayers were deposited without breaking vacuum at 100 °C. Al/TiN bilayers were then annealed at a constant ramp rate of 3 °C s−1 to 650 °C s−1 and the interfacial reaction between Al and TiN was monitored by in situ synchrotron x-ray diffraction measurements. As a reference point, we find that interfacial Al3Ti formation is observed at 450 °C in Al/TiN bilayers in which the TiN layer is deposited directly on SiO2 in a conventional magnetically balanced mode and, hence, is underdense with a mixed 111/002 orientation. However, the onset temperature for interfacial reaction was increased to 610 °C in bilayers with fully dense TiN exhibiting complete 111 preferred orientation.

The effect of arc ion pre-bombardment on the impact failure of TiN coating on Co-WC

Co-WC is increasingly used for precision dies and punches in semiconductor assembly process. The enhancement of impact resistance of hard layer coatings on Co-WC dies and punches is crucial for the application of hard coatings such as TiN. In this study, Co-WC has been deposited with a TiN film after Ti bombardment at various bias voltages of 0–750 V using the cathodic arc ion plating process. The surfaces' etching morphology and the temperature increase upon pre-bombardment with Ti ion onto Co-WC were evaluated by SEM and in-situ monitoring, respectively. The increase of bias voltage over 500 V significantly induced selective etching of Co and enhanced the substrate temperature higher than 300 °C in 10 min, thereby promoting the formation of a dense TiN film onto it. The prior etching of the surface by Ti ion bombardment with a high bias voltage was very effective in improving the adhesion of the TiN film on Co-WC and therefore reduced plastic deformation and crack density around the indentation area in a Rockwell C indentation test. The impact failure of a TiN coating on Co-WC could be consequently reduced under loads up to 150 N.

Wear of cermet cutting tools coated with physically vapour deposited TiN

Physically vapour deposition coated cutting tools presently take a large share of the cutting tool market. Recently, coated TiC-based cermets also appeared on the market, exhibiting cutting behaviour which makes them competitive with coated WC-based hardmetals. The present paper discusses the results of a study devoted to the wear mechanisms of TiN (physically vapour deposited) coated TiC-based cermets. Static diffusion experiments were conducted in order to simulate the diffusion process across the tool-workpiece interface at high temperature and pressure. Additionally, experimental uncoated and TiN-coated cermets were tested in machining steel, and the depth profiles of the worm edges were analysed. The diffusion couples and the worm cutting tools were analysed by scanning electron microscopy, energy-dispersive spectroscopy and Auger electron spectroscopy in order to identify the dominant wear mechanisms. The results of cutting tests with the experimental inserts confirmed the beneficial effect of TiN coating on the tool life of cermet cutting tools. At high cutting speeds the wear of uncoated and coated cermet tools is mainly determined by diffusion across the tool-workpiece interface. A TiN coating a high concentration of structural defects can only partially hinder diffusion. The association of defects enables the diffusion of carbon and nitrogen as well as metal atoms through the apparently dense TiN layer. However, outward nitrogen diffusion may prevent carbide grain decomposition, resulting in extended tool life.

A modified method for arc deposition of Ti-N thin films

Nearly stoichiometric dense Ti-N coatings with high microhardness and good adhesion on V2A substrates were deposited by reactive arc evaporation. Substantial reduction of the size and surface number density of macroparticle inclusions, deleterious for some thin film applications, was achieved by magnetic arc steering (using two low power consuming electromagnets) and by precise optimization of the reactive mode of deposition. The adhesion of the coatings on V2A substrates was improved by depositing two interlayers: one of pure titanium and another with graded composition, continuously varying from pure titanium to the composition of the final Ti-N coating. The arc technique proposed could find successful industrial application for low scale production of wear- and corrosion-resistant coatings.

Titanium nitride thin film deposition by laser CVD

Investigations aimed at the development of a laser induced chemical vapor deposition process for use in structured deposition of titanium nitride coatings on tool steel were performed. Experiments were carried out using a focused argon ion laser beam, where lateral film growth is realized by laser scanning. In particular, the deposition of titanium nitride from TiCl 4/N 2/H 2-precursor gas mixtures at atmospheric pressure was investigated. The deposited TiN films are adherent, hard, rough and porous. The double layer capacitance of those films is approximately one order of magnitude higher than that of smooth and dense TiN films. In order to estimate the laser induced temperatures in the film-substrate-system, lateral and temporal temperature fields were calculated.