High Nitrogen Flow Rate Research Articles

ALD and PVD Tantalum Nitride Barrier Resistivity and Their Significance in via Resistance Trends

Tantalum nitride (TaN) processes for barrier applications in advanced dual damascene Cu interconnect metallization schemes were developed and compared in order to study their electrical properties and the impact on via resistance. The limits of various physical vapor deposited (PVD) TaN processes in terms of resistivity were characterized, showing a rapid increase in TaN resistivity when DC sputtering is conducted with high nitrogen flow rates in an Ar/N2 plasma. More incorporation of nitrogen into TaN is observed at low PVD TaN deposition rates, established by applying low DC power sputtering conditions. Via resistance measurements were performed on dual damascene via structures built with either Ta-rich PVD TaN films with a resistivity of ~240 μΩcm, or ALD TaN films with a resistivity of ~5000 μΩcm as barriers. Even though the resistivity of ALD TaN blanket films is significantly higher than PVD TaN, reduced via resistance values were observed as a larger fraction of PVD TaN in the barrier stack was replaced by ALD TaN. For a TaN barrier at 3nm thickness, the via resistance measured for ALD TaN was ~28% lower than its PVD counterpart.

Reaction of enargite (Cu3AsS4) in hot concentrated sulfuric acid under an inert atmosphere. Part III: reaction stoichiometry and kinetics

Based on the extensive insights gained from the acid bake–leach reaction from our previous experiments, a rigorous experimental plan was designed to investigate the effects of time, temperature, particle size, nitrogen flow rate, sulfuric acid concentration and dosage, and reaction surface area on the extraction of Cu and As from a high-quality enargite sample through sulfuric acid baking and leaching. The baking experiments in the temperature range of 170–200°C over 1–4h revealed almost complete Cu and As extraction after 4h baking at 200°C, a sulfuric acid to enargite weight ratio (S/E) of 4, nitrogen flow rate ~100mL/min, and particle size P100=−45μm, and no arsenic was lost to the gas phase. The following reaction is suggested for the sulfuric acid baking of enargite:4Cu3AsS4+28H2SO4=3CuO•CuSO4+6CuSO4+2As2O3+28H2O+19.5SO2g+15.5SLack of a systematic dependence of reaction rate on particle size and the significant dependence of the rate on sulfuric acid concentration suggest that the rate of the baking reaction is controlled by the internal surface area of cracks at which surface the baking reaction occurs. It is expected that these cracks are formed as a result of a major volume increase during the baking reaction. High nitrogen flow rates encouraged arsenic loss to the gas phase. Decreasing the S/E ratio from 4 to 2 resulted in a decrease in the rate of reaction, while increasing sulfuric acid concentration enhanced the rate. Excess sulfuric acid was found to be necessary for both acceptable reaction rates and also for maximum As retention in the condensed phase. Doubling the reaction surface area did not affect the extraction of Cu and As.

Structural State and Mechanical Characteristics of the ZrN Films Prepared by Sputtering

ZrN films were prepared by magnetron sputtering on die steel substrates. The objective of this study was to investigate the effect of nitrogen flow rate on the microstructure ,morphology, nanohardness properties determined by X-ray diffraction, field-emission scanning electron microscope, nanoindentation, and pin-on-disk, respectively. The XRD shows that ZrN has (111) and (200) preferred orientation under lower nitrogen flow rates. The surface of coatings revealed smaller grains and uniform dense under lower nitrogen flow rates. With increasing the nitrogen flow rates, this result showed ZrN films lead to poor mechanical properties and hardness values. However, films consisted of up high ernitrogen flow rate had much lower friction coefficient.

Effect of N<sub>2</sub> Flow Rates on Properties of Nanostructured TiAlN Thin Films Prepared by Reactive Magnetron Co-Sputtering

The TiAlN thin films with different crystal structure, surface morphology, microstructure and chemical compositions were deposited on Si (100) plane by changing the N2 flow rate from 2 to 10 sccm using co-targeted reactive magnetron sputtering technique in the same process. The effect of nitrogen flow rate on structure and properties of TiAlN thin films was investigated in the study. The films were characterized by X-ray Diffraction (XRD), Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) techniques, respectively. The results show that the crystal structure, surface morphologies microstructure and chemical compositions of the film are strongly depended on the N2 flow rates. The (111) (200) and (220) planes of TiAlN thin films were found with different nitrogen flow rates, one is the preferred orientation of (111) plane that appeared for nitrogen flow rates of 2 sccm, the other one is the preferred orientation of (200) plane for the higher nitrogen flow rates of 4-10 sccm. The crystal size of the films was also determined by Scherrers equation, varied between 13.8 - 35.6 nm. The roughness of the as-deposited films was ranging from 1.8 to 4.3 nm. The chemical compositions of TiAlN were depended on N2 flow rates. The microstructure and cross-sectional SEM analysis revealed that the nanograins were developed and thickness decreased from 381 nm to 131 nm. In addition, the columnar structures were observed for all films.

Improving the gas barrier properties of a-SiOxCyNz film at low temperature using high energy and suitable nitrogen flow rate

Amorphous silicon oxycarbonitride thin films were synthesized on polyethylene terephthalate (PET) substrates at low temperatures (∼80 °C) by plasma-enhanced chemical vapor deposition (PECVD). A high ion flux and suitable nitrogen flow rate improved the gas barrier properties and deposition rate of the resulting a-SiOxCyNz film. The a-SiOxCyNz films were deposited at a high deposition rate and low water WVTR properties as a result of the high ion flux and nitrogen chemistry. The high ion flux modified the chemical structure and nitrogen atomic composition of the resulting a-SiOxCyNz film coatings. The substrate temperature was characterized using a thermometer. In addition, the coating properties were characterized by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and the water vapor transmission rate (WVTR).

Characterization of nitrogen doped p-type ZnO thin films prepared by reactive ion beam sputter deposition

Nitrogen doped ZnO (ZnO:N) thin films have been successfully prepared by reactive ion beam sputter deposition. The ZnO:N thin films show a preferred growth orientation along the (002) direction regardless of nitrogen flow rates. Raman spectroscopy analysis shows nitrogen related local vibration modes at 275 and 576cm−1 in addition to the ZnO E2 (high) mode at 436cm−1, indicating a successful incorporation of nitrogen into the ZnO. Both of the peak intensities of 275 and 576cm−1 reach a maximum after post-growth annealing at 500°C. ZnO:N deposited with a 0.5sccm nitrogen flow rate exhibits p-type conductivity with a hole concentration of 2.1×1017/cm3 and a mobility of 3cm2V−1s−1 after annealing at 500°C. Conversion to p-type conductivity was not observed on ZnO:N deposited with higher nitrogen flow rates. The p-type conductivity remains stable after it was stored at ambient conditions for more than two months. The p-type ZnO:N thin film is transparent in the visible range with a transmittance larger than 83%. SIMS analysis indicates that nitrogen concentration of less than 1.2at.% results in the successful preparation of p-type ZnO:N. ZnO:N deposited with higher nitrogen concentration results in n-type conductivity which is likely due to the formation of molecular nitrogen replacing oxygen sites that act as double donors (N2)O.

Synthesis of TiN/Ti3Al composite coatings on Ti6Al4V alloy by plasma spraying and laser nitriding

The aim of this paper was to develop an in situ method to synthesize the TiN reinforced Ti3Al intermetallic matrix composite (IMC) coatings on Ti6Al4V alloy substrate by using plasma spraying and laser nitriding. The microstructure and mechanical properties of TiN/Ti3Al IMC coatings synthesized at different nitrogen flow rates (NFRs) in laser nitriding were investigated. Results showed that the crack- and pore-free IMC coatings can be made through the proposed method. The morphology of TiN phase and mechanical properties of coatings were strongly dependent on nitrogen NFR in nitriding. The TiN phase exhibited dendrite-like and undeveloped morphology at low nitrogen NFR. At high NFR, the TiN phase showed granular-like morphology. With increasing NFR, the amount of TiN phase in the coating increased, leading to the increment of microhardness and elastic modulus and the decrement of fracture toughness of coating.

Comparison of Oxidation and Microstructure of Warm-Sprayed and Cold-Sprayed Titanium Coatings

Thick titanium coatings were prepared by the warm spraying (WS) and cold spraying (CS) processes to investigate the oxidation and microstructure of the coating layers. Prior to the coating formations, the temperature and velocity of in-flight titanium powder particles were numerically calculated. Significant oxidation occurred in the WS process using higher gas temperature conditions with low nitrogen flow rate, which is mixed to the flame jet of a high velocity oxy-fuel (HVOF) spray gun in order to control the temperature of the propellant gas. Oxidation, however, decreased strikingly as the nitrogen flow rate increased. In the CS process using nitrogen or helium as a propellant gas, little oxidation was observed. Even when scanning electron microscopy or an x-ray diffraction method did not detect oxides in the coating layers produced by WS using a high nitrogen flow rate or by CS using helium, the inert gas fusion method revealed minor increases of oxygen content from 0.01 to 0.2 wt.%. Most of the cross-sections of the coating layers prepared by conventional mechanical polishing looked dense. However, the cross-sections prepared by an ion-milling method revealed the actual microstructures containing small pores and unbounded interfaces between deposited particles.

Role of Temperature and Nitrogen Flow Rate During the Carbothermic Synthesis of SiC/Si3N4 Nanocomposite Powder from Gel

This research article explores the synthesis of SiC/Si3N4 nanocomposite powder via a carbothermic reaction of silica xerogel under nitrogen atmosphere. The influence of both reaction temperature and nitrogen flow rate on the properties of the produced sample was thoroughly investigated. The results revealed that both reaction temperature and nitrogen flow rate played a very important role not only on the composition ratio of SiC/Si3N4 in the finally produced sample but also on the morphology of both phases. At 1300°C, spherical particles of 40 nm grain size for both phases (SiC and Si3N4) were produced, while silicon nitride is the predominant phase. With increasing the reaction temperature, the amount of SiC increased at the expense of the amount of Si3N4 till SiC becomes the predominant phase at 1500°C. At 1500°C, almost both phases have the shape of nanorods with different grain sizes. At low nitrogen flow rate and reaction temperature of 1500°C, SiC predominates while with increasing nitrogen flow rate the Si3N4 becomes the predominant phase. The photoluminescence spectra revealed that a strong emission was observed at 354 and 389 nm for the sample produced at low and high N2 flow rate, respectively. On the other hand, a high surface area of 578 and 471 m2/g were produced for samples prepared under low and high nitrogen flow rate, respectively. Also, the mechanism of formation of the SiC/Si3N4 nanocomposite powder was postulated.

Electrical and reliability performances of nitrogen-incorporated silicon carbide dielectric by chemical vapor deposition

The influence of nitrogen flow on the electrical properties of silicon carbide (SiC) barrier dielectrics prepared by plasma-enhanced chemical vapor deposition was reported. Experimental results showed that the leakage current and dielectric constant of the SiC film are reduced by increasing nitrogen flow rate. The thermal stability of the SiC film is greatly improved by doping nitrogen. The reliability of SiC barrier dielectrics deposited at various nitrogen flow rates was also investigated. The performance of dielectric breakdown is significantly improved for the nitrogen-incorporated SiC film due to its better capability in preventing copper (Cu) thermal diffusion. In addition, Cu electromigration performance is slightly enhanced by capping the SiC film deposited at a higher nitrogen flow rate because of the reinforcement of bonding strength with Cu.

Influence of the nitrogen flow rate on the order and structure of PECVD boron nitride thin films

Three sets of boron nitride (BN) thin films are deposited with different N 2 /B 2 H 6 flow ratios ( r = 4, 10 and 25) by plasma enhanced chemical vapor deposition (PECVD). The variations of physical properties in different deposition sets are analyzed by optical (XPS, FTIR, UV–visible spectroscopies), mechanical and electrical measurements. The films are considered to be deposited in a turbostratic phase (t-BN). Evolution of bonding configurations with increasing r is discussed. Relatively higher nitrogen flow rate in the source gas mixture results in lower deposition rates, whereas more ordered films, which tend to reach a unique virtual crystal of band gap 5.93 eV, are formed. Anisotropy in the film structure and film inhomogeneity along the PECVD electrode radial direction are investigated.

Effects of Temperature of In-flight Particles on Bonding and Microstructure in Warm-Sprayed Titanium Deposits

Micron-sized titanium particles were deposited on steel substrates by the warm spraying, which is a modified high velocity oxy-fuel (HVOF) spraying technique. In the process, nitrogen gas is mixed with the HVOF flame jet to lower the temperature of injected powder particles. Detailed observations of splats formed on polished substrates by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to investigate the effects of particle temperature on the bonding of splats with the substrate and the microstructure within the splats. At lower nitrogen flow rates, the particles observed were heavily deformed and exhibited diverse splat morphologies and microstructures. At higher nitrogen flow rates, most of the particles were impacted in the solid state and the oxidation of particles was remarkably less. The TEM observation revealed distinctively different microstructures within the splats as well as the splat/substrate interfaces depending on whether the particle was molten or solid before the impact.

Effect of thermal treatments on the structure of MoN xO y thin films

MoN x O y films were deposited on steel substrates by dc reactive magnetron sputtering. The depositions were carried out from a pure molybdenum target, varying the flow rate of reactive gases. X-ray diffraction (XRD) results revealed the occurrence of cubic MoN x and hexagonal (δ-MoN) phases for the films with high nitrogen flow rates. The increase of oxygen content induces the decrease of the grain size of the molybdenum nitride crystallites. The thermal stability of a set of samples was studied in vacuum, for an annealing time of 1 h, for temperatures ranging from 500 to 800 °C in 100 °C steps. The results showed that pure molybdenum nitride films changed their structure from a meta-stable cubic MoN to hexagonal δ-MoN and cubic γ-Mo 2N-type structures with increasing annealing temperatures. The samples with molybdenum nitride films evidenced a good thermal stability, but those with molybdenum oxynitride coatings showed a tendency to detach with the increase of the annealing temperature.

Characterization of zirconium nitride films sputter deposited with an extensive range of nitrogen flow rates

Zr N x films are deposited by rf magnetron sputtering using a wide range of nitrogen flow rates to control film properties. Scanned probe microscope (SPM) oxidation is presented as a complimentary characterization tool to x-ray diffraction, colorimetric, and four point probe analyses. The SPM oxidation behavior of the ZrNx films is related to their structural, optical, and electrical properties. Whereas stoichiometric ZrN films have applications as protective and/or decorative coatings, ZrNx films sputtered with higher nitrogen flow rates have potential applications in devices where arrays of high aspect ratio nanostructures would be useful.

Structural properties and electrical resistivity of TiNx and Ti1−xAlxN films prepared by reactive dc magnetron sputtering: effect of nitrogen flowrate

Nanocrystalline thin films of titanium nitride and titanium aluminium nitride were deposited on (111) Si substrates by reactive dc magnetron sputtering under various nitrogen flowrates and at constant substrate temperature. The effect of nitrogen flowrate on the structural and electrical properties of TiNx and Ti1−xAlxN thin films deposited at substrate temperatures of 973 and 773 K respectively is investigated. TiNx films are polycrystalline at all N2 flowrates and there is a change of preferred orientation from (200) to (111) with increasing nitrogen flowrates. In contrast, Ti1−xAlxN thin films are polycrystalline only at low nitrogen flowrates (<5 sccm) and show a tendency to become more nanocrystalline with weak (200) preferred orientation at higher nitrogen flowrates. The variation of lattice parameter showed opposite behaviour in these two types of films. Auger electron spectroscopy indicated that the nitrogen concentration of both types of the films gradually increased with increasing nitrogen flowrate and almost reached a constant value at a flowrate of nitrogen ≥5 sccm. While the resistivity of TiNx films showed a minimum at a nitrogen flowrate of 5 sccm, the resistivity of Ti1−xAlxN films increased with increasing nitrogen flowrate. The variation in the electrical resistivity could be explained on the basis of structural changes occurring in these two types of films.

Hard plasma chemical coatings based on silicon carbon nitride

Silicon carbon nitride (SiCN) coatings deposited on a silicon substrate are produced by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS), nitrogen, and hydrogen as starting materials. The coatings are characterized with AFM, XRD, and FTIR. Their mechanical properties are determined with nanoindentation. The abrasion wear resistance is examined using a ball-on-plane (calowear) test and adhesion to the base using a scratch test. The x-ray diffraction indicates that the coatings produced at moderate FN are nanostructured and represent β-C3N4 crystallites embedded into the amorphous a-SiCN matrix. The coatings deposited at a higher nitrogen flow rate are amorphous. The nanostructure is supposed to result from an increase in hardness (25 GPa) and Young’s modulus (above 200 GPa). The tribological tests have revealed that the friction coefficients of the coatings containing nitrogen are two to three times smaller than those based on SiC and deposited on a silicon substrate. The ball-on-plane tests show that the nanostructured coatings also exhibit the highest abrasive wear resistance. These findings demonstrate that the SiCN films deposited using MTCS show good mechanical and tribological properties and can be used as wear-resistant coatings.

Properties of SiOxNy Thin Films Deposited with a Single Molecular Precursor by Using RF PECVD

We have deposited SiOxNy thin films on both Si(100) and glass substrates by using a tetraethyl orthosilicate (TEOS) single precursor at nitrogen flow rates of 0 ∼ 100 sccm by using a radiofrequency Plasma Enhanced Chemical Vapor Deposition (PECVD) method. The film growth orientation and microstructural characteristics were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Deposition at higher nitrogen flow rates results in finer clusters with smaller grain sizes. Moreover, we used UV/Vis and FT-IR spectroscopy and ellipsometry to investigate the optical properties for various nitrogen flow ratios. As-deposited SiO2 films showed an amorphous structure, but samples annealed in an O2 ambient at 900 ◦C showed increased crystallinity. Also, the leakage current densities of the SiO2 and the SiOxNy films annealed at 900 ◦C in an O2 ambient were about 4.0 × 10−8 and 1.5 × 10−7 A/cm.

Visible light-active nitrogen-doped TiO 2 thin films prepared by DC magnetron sputtering used as a photocatalyst

The visible light-active nitrogen-doped TiO 2 has been prepared by dc-reactive magnetron sputtering using Ti target in an Ar+O 2/N gas mixture. The preparation of highly crystallized anatase TiO x N y thin films with various nitrogen concentrations allowed us to identify the optimum nitrogen flow ratio for the photocatalytic oxidation (PCO) of 2-propanol. At higher nitrogen flow rate, nitrogen is found to be difficult to substitute for oxygen having been predicted to contribute the band gap narrowing, giving rise to undesired deep level defects. In addition, Raman spectroscopy and X-ray diffraction (XRD) studies revealed that highly crystallized anatase growth of nitrogen-doped TiO x N y thin films are difficult at higher nitrogen flow rate. The optical band gap was found to be lower for the films deposited at 2 sccm of nitrogen flow rate. The PCO of 2-propanol was studied as a function of nitrogen flow rate using in situ FTIR spectroscopy. The PCO of 2-propanol found to proceed along two routes: one was through the chemisorbed species, 2-propoxide to form the CO 2 directly; the other was through conversion of 2-propanol to acetone, followed by formation of formate species, and finally CO 2.

Relationship between composition, bonding constitution and microstructure in unbalanced magnetron sputtered Ti–B–N thin films

Two types of Ti–B–N thin films with different B contents were deposited on Si(100) at room temperature at different nitrogen flowrates. Their phase configurations and microstructures were subsequently characterised. The results indicated that the nitrogen flowrate greatly affected phase configuration and film composition. At a low nitrogen flowrate, TiN bonding was preferentially formed, accompanying with small amounts of TiB and TiB2 bonds. Formation of TiB2 bonding was accelerated with increasing B content. Nanocomposite thin films mainly consisting of nanocrystalline (nc-) TiN/amorphous (a-) TiB2 were finally formed. At a high nitrogen flowrate, TiN followed by BN was first formed, accompanying with small amounts of TiB and TiB2 bonds. Formation of BN bonding was further accelerated with increasing B content. Nanocomposite thin films mainly consisting of nc-TiN and a-BN were finally produced. The present thin films are the nanocomposite of nc-TiN embedded in the a-matrix with a dense microstructure despite of the nitrogen flowrate.

The role of oxygen in thiosulphate leaching of gold

The role of oxygen in thiosulphate leaching of gold has been investigated in both pure gold and ore systems. The gold dissolution decreased in the presence of oxygen in the pure gold system. Air or oxygen bubbling caused higher consumption of thiosulphate and leaching passivation. Nitrogen bubbling largely increased gold dissolution and this beneficial effect appeared to be more noticeable at a higher nitrogen flowrate. Nitrogen bubbling stabilised thiosulphate and prevented the passivation of gold. The use of oxygen pre-saturated water had little effect on gold dissolution. The counter current leaching tests showed that both gold passivation and the products due to thiosulphate decomposition affected the gold dissolution. The leaching solutions could be re-used without any impact on gold dissolution under a nitrogen atmosphere. Mineralogy affected the thiosulphate leaching system under different atmospheres. The leaching behaviour of a sulphide ore with only a small amount of sulphides was determined by the leaching behaviour of gold. However, air bubbling gave a higher overall recovery in the leaching of a pyrite concentrate, while nitrogen bubbling only marginally increased the overall gold recovery. Oxygen injection enhanced the dissolution of sulphides, releasing more gold from the sulphide matrices. Nitrogen injection hindered the corrosion process of the sulphides, affecting the overall gold recovery. Nitrogen bubbling decreased the thiosulphate consumption in the leaching of the pyrite concentrate, while air bubbling increased the thiosulphate consumption. It is suggested that high sulphide containing ores should be pre-treated to fully or partially break down the sulphide matrices to liberate gold, followed by gold leaching under a nitrogen atmosphere.