TaN Films Research Articles

Improvement of thermal stability of Ta-N film in Cu metallization by a Zr-Si interlayer

Ta-N (10 nm)/Zr (20 nm) film was grown on n-type (100) silicon wafer at various substrate temperatures in a rf magnetron sputtering system, followed by in situ deposition of Cu. The Cu/Ta-N/Zr/Si samples were subjected to thermal annealing up to 800 ℃ under the protection of pure nitrogen gas. In order to investigate the effect of insertion of a thin Zr layer under Ta-N film on Ta-N diffusion barrier performance in Cu metallization, Cu/Ta-N/Zr/Si contact system was characterized by X-ray diffraction (XRD), four-point probe (FPP) measurement, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES) depth profile. The results reveal that the microstructure of Ta-N films deposited on Zr is amorphous at different substrate temperatures. The barrier breakdown temperature of Ta-N/Zr film is about 100°C higher than that of Ta-N. It can effectively prevent the diffusion of Cu after annealed at 800°C. The improvement of diffusion barrier performance may be due to the production of Zr-Si layer with low contact resistivity after annealed at 800°C.

Microstructure and electrical property of tantalum oxynitride thin films prepared using high-power impulse reactive magnetron sputtering

Ta-N thin films were prepared on glass and Al2O3 substrates using high-power impulse reactive magnetron sputtering. A Ta target was used and sputtered using Ar/N2 two gasses mixture. The phase structures, microstructures and electrical properties of Ta-N thin film with different powers and annealing temperatures were investigated. The results showed that an amorphous structure existed in the as-deposited Ta-N films at 500 W, and some crystalline phases (TaN, Ta2N and β-Ta) were observed in as-deposited films at 1500 W and 2500 W. The crystallization phase did not change when the annealing temperature ranged from room temperature up to 500 °C. When the sputtering power increased to 2500 W, TaN, Ta2N and β-Ta crystalline phases coexisted in the as-deposited films. However, Ta-N films deposited at 2500 W and annealed at 500 °C in N2 exhibited resistivity of ∼460 μΩ-cm with −93 ppm °C−1 temperature coefficient of resistance.

Atomic layer deposition of TaN thin film on Ti–6Al–4V dental implant for enhanced anti-corrosion and anti-bacterial properties

TaN thin film was deposited on a Ti–6Al–4V plate, a widely used material for the dental implant. The surface morphology and thickness of the TaN thin film were investigated by Scanning Electron Microscopy (SEM). The surface chemical states and elemental composition were studied by X-ray photoelectron spectroscopy (XPS). The crystal structure was determined by X-ray Diffraction (XRD) patterns. The water contact angles of both Ti–6Al–4V and TaN surface were measured. The anti-corrosion behaviors of Ti–6Al–4V and TaN were studied through electrochemical characterization in the artificial saliva environment, and the anti-bacteria behaviors were investigated with both bacteria of E. coli and S. aureus.

Enhanced self-lubricating and antibacterial activity by building hard-yet-tough Ta-Ag-N films on Ti-6Al-4V

The poor self-lubricating behavior and antibacterial activity of Ti-6Al-4V alloy hinder its medical applications in surgical instruments. And thus, Ag-based transition metal nitrides nanocomposite films on Ti-6Al-4V substrate where Ag existed in the form of nanoparticles have been commonly employed to improve the above properties. In this work, two kinds of Ag-based TaN films (~3 at.% Ag) with solute Ag atoms and Ag nanoparticles are respectively fabricated on the surface of Ti-6Al-4V alloy by magnetron sputtering, aiming to insight into their self-lubricating behavior and antibacterial activity. It is revealed that as Ag resides in form of solute atoms rather than nanoparticles in Ta-Ag-N films, the enhanced antibacterial activity, lower coefficient of friction (CoF) coupled with raised hardness (~39 GPa) and enhanced toughness can be achieved. Compared with the Ag nanoparticles, solute Ag atoms are considerably easier to form Ag2O in the atmosphere and to produce self-lubricating silver tantalate (AgTaO3) phase during the sliding, respectively contributed to the enhanced antibacterial activity and the drop in CoF. It suggests that the new strategy of incorporating solute Ag atoms into TaN can improve its self-lubricating ability and antibacterial activity for possibly extending the surgical instruments service life and reducing healthcare costs.

Deposition of TaN Film on Commercial Pure Titanium Disk by Modified Reactive Plasma Sputtering Technique

Background: The new trend of implants is to find materials which accelerate bone formation at bone implant interface and improve Osseo integration to provide immediate or early loading after placement and eliminate waiting period which is uncomfortable and disturbs patients. Titanium as an implant material still need some improvement of surface properties physically and chemically. Tantalum which is gaining more attention as a new metallic biomaterial. Coating layer over implant is an important way for improvement of surface properties of titanium. Plasma used for surface modification, has several advantages such as changing surface topography, increasing surface roughness and in increasing the wettability of the surface. Aim of study: To evaluate the effect of TaN coating by modified plasma sputtering technique of commercially pure titanium disk on wettability, surface roughness, surface chemical composition in comparison to noncoated surface. Materials and methods: Two groups were tested in this study which include non -coated commercial pure titanium disks and coated commercial pure titanium with TaN. Modified reactive plasma sputtering apparatus was used to coat CpTi with TaN at 4, 6 &8, h. Surface characterization by x-ray diffraction (XRD) analysis, scanning electron microscope (SEM), energy dispersive spectroscopy(EDS), contact angle measurement, were carried out for coated and uncoated disks. Results: The result of coating specimen with TaN at times (4,6&8) h showed that 8 h coating time was the best time. And this was according to the results of X-ray diffraction analysis which show a new peak formation of Ta N coated CpTi disk which was not present in non- coated CpTi disk. The results of wettability test for CpTi disk coated with TaN disk was more than wettability of non- coated CpTi disk. Surface Roughness was more and better distributed in CpTi coated with TaN disk than non- coated one which appear clearly in electron microscope.

Influence of TaN films deposited using different N2 flow rates on the properties of Ta and Cu films in advanced 3D NAND memory

In this work, the properties of Ta and Cu films on TaN films deposited using different N2 flow rates were explored. The phase identification of Ta, sheet resistance (Rsh) of Ta/TaN stacking films, as well as the N contents within TaN films were characterized using X-ray diffraction (XRD), precession electron diffraction (PED), transmission electron microscope (TEM), four-point probe measurements and X-ray photoelectron Spectroscopy (XPS), respectively. It was found that the N contents within TaN films increase with increased N2 flow rate, and the formation of low resistivity α-Ta phase was enhanced on such TaN films with higher N contents. Furthermore, how the Ta/TaN stacking films affecting the orientations of Cu seeds and subsequent electroplated Cu films was investigated by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). It was demonstrated that both Cu seeds and electroplated Cu films possess dominant Cu(111) orientation but this orientation decreases with increased N2 flow rate during the deposition of TaN.

Design and fabrication of a 4-bit RF MEMS attenuator with a high attenuation accuracy

This paper presents a 4-bit micro-electromechanical system (MEMS) digital attenuator with improved attenuation accuracy by surface micromachining. The attenuator is consisted of monoblack type radio frequency MEMS switches and TaN film resistors fabricated on a glass substrate to control the reconfigurable power within DC ~ 18 GHz. The simulation results revealed that the device had favorable terminal matches ranging from 0 to 70 dB with a 10 dB step. The attenuation accuracy was better than 1.2 dB, the insertion loss was less than 1.32 dB, and the voltage standing wave rations were better than 1.56 under these eight attenuation steps. Additionally, the package size of this device was designed as 8.28 mm × 2.37 mm × 0.85 mm, such that it could be applied to miniaturized microwave instruments.

Deposition of TaN Film on Commercial Pure Titanium Disk by Modified Reactive Plasma Sputtering Technique

Deposition of TaN Film on Commercial Pure Titanium Disk by Modified Reactive Plasma Sputtering Technique

Large influence of vacancies on the elastic constants of cubic epitaxial tantalum nitride layers grown by reactive magnetron sputtering

We report a comprehensive study on the structure and elastic constants of epitaxial cubic δ-TaxN (x ≈ 1) layers deposited by reactive magnetron sputtering at 570 °C on MgO(001), MgO(110) and MgO(111) substrates. X-ray diffraction shows that all layers are single-phase and have a single-crystal rocksalt-structure, growing with an epitaxial cube-on-cube relationship with respect to their MgO substrates. For (001)-orientation, Brillouin light scattering provides the measurement of c44 (137 ± 3 GPa) and c12 (130 ± 5 GPa) single-crystal elastic constants, while picosecond laser ultrasonics (PLU) provides the third independent one, c11 (530 ± 10 GPa). For (110)- and (111)-orientations, PLU provides selectively the following combinations, (c11+c12+2c44)/2 and (c11+2c12+4c44)/3, respectively. Electrical resistivity measurements show evidence of point defects in the films despite a composition close to 1:1 stoichiometry. Point defects (metal and nitrogen vacancies) are considered in our first-principles calculations to find closer agreement between experimental and theoretical lattice parameter, mass density, sound velocities and elastic constants. Sound velocities and elastic constants are found to be particularly sensitive to the presence of vacancies, resulting into a more compliant and less anisotropic material. While only ∼ − 1% mismatch is found between predicted defect-free and experimental lattice parameters, huge differences of −27% and +180% are observed for c11 and c44, respectively. These discrepancies can be rationalized by considering the presence of point defects (metal vacancy and/or Schottky defect) in concentration ∼11% in the as-deposited TaN films, a compositional value that corresponds to the lowest formation energy of δ-TaNx structure.

Effect of bias voltage on microstructure and properties of magnetron sputtering TaN coating

A series of TaN films were coated on Al2O3 at various bias voltages by magnetron sputtering technique. Effect of bias voltage on the microstructure, roughness, deposition rate, binding force of coating-substrate, electrical properties of the TaN coating were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), profile meter, scratch tester and four points probe respectively. The results suggest that the TaN coating were formed by face-center δ-TaN crystals and the preferential orientation of the coatings varied with the bias voltage; the deposition rate and the binding force of coating-substrate reached maximum value of 5.71nm/min and 4.5N when the bias voltage was 80 V, the roughness and the square resistance reached the minimum value of 0.509nm and 15.58Ω/□

Thermal stability of tantalum nitride based thin film resistors

Tantalum nitride thin films were deposited on Al2O3 substrates by the dc-magnetron sputtering technique. The nitrogen content in the argon/nitrogen flow varied from 5 to 50%. Structural properties were studied using X-ray diffraction. The ratio of Ar:N2 was 4:1; the ratio of Ta:N became 1:1. Sheet resistance depends on thickness and is in the range of 20 – 80 Ω/□ due to thickness 100 – 50 nm. The TaN films deposited at a nitrogen/argon ratio of 20% show the thermal stability of the resistance in the 25–400°C temperature range. Sheet resistance degradation was ∼ 5%. The TCR value was determined in the range of 25 – 300 C and was equal to - 21 ppm/K.

Plasma-enhanced Atomic Layer Deposition of TaN Film and Its Resistance to Copper Diffusion

Plasma-enhanced Atomic Layer Deposition of TaN Film and Its Resistance to Copper Diffusion

Post-CMP Cleaning Solutions for the Removal of Organic Contaminants with Reduced Galvanic Corrosion at Copper/Cobalt Interface for Advanced Cu Interconnect Applications

It has been difficult to remove BTA-related organic residues (BTA, Cu-BTA, and Co-BTA complexes) and silica abrasives from various surfaces during post Cu-CMP cleaning when Co is used as the liner. Here, we investigated the adsorption of these residues and their removal from Cu, Co, TaN and SiO2 films for Cu interconnect applications. A 50 mM aqueous solution of ethylenediamine (En) at pH 11, aided by ultrasonic agitation, almost completely removed these contaminants adsorbed on only Cu and Co films. Cleaning was facilitated by the much higher stability constants of Cu-En/Co-En complexes compared to those of Cu-BTA/Co-BTA complexes, which led to their dissociation via ligand exchange. En also lowered ΔEcorr of the Cu/Co couple to ∼40 mV but their Icorr values remained high. Cysteine (Cys) and uric acid (UA) were effective in controlling the cathodic and anodic reactions of Cu and Co films. An aqueous mixture of 0.75 mM Cys, 9.25 mM UA and 50 mM En at pH 11 not only removed the organic residues and silica particles from Cu and Co films but also lowered ΔEcorr between them to ∼5 mV with an Igc of ∼0.7 μA/cm2, acceptably low Icorr values for both films with excellent surface quality.

Schottky barrier height modulation effect on n-Ge with TaN contact

TaN film with various N contents was formed to provide ohmic contact on n-type Ge. Schottky barrier heights (SBH) of the TaN/n-Ge and TaN/p-Ge contacts were carefully investigated by low-temperature I-V measurement. The SBH was modulated from 0.54 eV for Ta/n-Ge to 0.30 eV for TaN/n-Ge. The SBH lowering on n-Ge was found to be linear with the N contact x in TaNx, which confirmed the interfacial dipoles layer model. Deposition of TaN on plasma-treated Ge surface showed that the surface damage is not the reason for the low SBH on n-Ge. On the contrary, SBH modulation effect vanished on the rough Ge surface due to deconstruction of the interfacial dipoles layer.

(Invited) Apprehension of Large Coercive Field in Ferroelectric HfO2 Thin Films

A special feature of ferroelectric HfO2 films is that they have large coercive fields (EC), as large as 1 MV/cm and more. A merit of the large coercive field is that a sufficient memory window is attainable even in ultrathin films. For example, a 2-V-memory window is available by 10-nm-thick Hf-Zr-O ferroelectric film. Compared with the conventional ferroelectric oxide capacitors using Pb(Zr, Ti)O3 and SrBi2Ta2O9 that applies around 100-nm-thick films, the ferroelectric HfO2 films contribute to the scaling of film thickness about one order. It is attractive for the development of high-density non-volatile memories integrated on LSI. On the other hand, the large coercive fields of ferroelectric HfO2 films bring serious concerns such as breakdown and endurance in capacitors. In this work, we studied the influence of large coercive fields on the endurance properties of Hf-Zr-O capacitors. Metal-ferroelectric-metal (MFM) capacitors that consist of TaN/Hf-Zr-O/TaN were prepared on heavily doped Si substrates. TaN electrode films were deposited by DC sputtering, using Ta target and mixture gas of Ar and N2. Hf-Zr-O films were prepared by RF sputtering, using HfO2 and ZrO2 targets and Ar gas. The metal composition was adjusted to Hf : Zr=50 : 50, and the thickness is 10 nm. After deposition of the top TaN film, crystallization anneal was processed in a vacuum condition at 700 degree Celsius. Finally, top electrodes were patterned by photolithography and dry etching. Ferroelectric properties of 10-nm-thick Hf-Zr-O capacitors were investigated by the polarization-voltage measurements. The ECvalue of this capacitor was evaluated to be 1 MV/cm. The electrical breakdown by the DC mode was measured to be about 4 MV/cm. Remnant polarization (Pr) and endurance properties of the capacitors are summarized in the figure. The Pr is faint when the applied electric field is less than the EC. The Pr value increases drastically when the electric fields are set between EC and 2xEC, and then gradually saturates over 2xEc. Thus a larger electric field is favorable for the achievement of large and stable polarization. In contrast, the endurance characteristics show a negative trend with the electric field. The endurance cycle as large as 108 was observed when the electric field is 2xEC, but it decreases drastically with the increment of electric field over 2xEC. It indicates that the capacitors are damaged even when the electric field is much lower than the breakdown field. Although a better endurance is expected at electric field lower than 2xEC, it makes a sacrifice of the Pr value and the stability. This trade-off relationship is considered to be a critical hurdle for the application of ferroelectric HfO2 capacitors. This work was supported by JST CREST Grant Number JPMJCR14F2, Japan. Figure 1

Reactive B/Ti Nano-Multilayers with Superior Performance in Plasma Generation.

In this study, reactive B/Ti nano-multilayers were fabricated by magnetron sputtering and the structure and chemical composition were confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analyses. The periodic multilayer structure can be clearly visible, and the multilayer material is composed of B layers (amorphous), Ti layers (nano-polycrystalline), and intermixed reactants in a metastable system. The as-deposited B/Ti nano-multilayers exhibit a significantly high heat release of 3722 J/g, with an onset reaction temperature of 449 °C. On the basis of these properties, an integrated microigniter was designed and prepared by integration of the B/Ti nano-multilayers with a TaN film bridge for potential applications in plasma generation, and the electric ignition processes were investigated with discharge voltages ranging from 25 to 40 V. The integrated microigniter exhibits improved and stable ignition performances with a short burst time, high plasma temperature, and violent explosion phenomenon in comparison with the TaN film igniter. Overall, the plasma generation of the microigniter can be enhanced substantially by integration with the B/Ti nano-multilayers.

Low resistivity Ta textured film formed on TaN

Ta films formed on Si(100) and quartz substrates by sputtering technique usually lead to a textured β-Ta with tetragonal crystal lattice. The β-Ta film has a high resistivity. As a comparison, low resistivity α-Ta with cubic crystal lattice can be formed by sputtering on TaN. Crystal study shows that the sputtered TaN film has a preferred (111) growth plane and the α-Ta has a preferred (110) growth plane. Both are textured films. The growth mechanism of the α-Ta on TaN is ascribed to epitaxy.

Characterization of tantalum and tantalum nitride films on Ti6Al4V substrate prepared by filtered cathodic vacuum arc deposition for biomedical applications

This paper explores tantalum and tantalum nitride thin films produced by filtered cathodic vacuum arc deposition method as bio-stable surface treatment for Ti6Al4V titanium alloy. Effect of nitrogen to argon gas ratio on microstructure of the deposited film has been investigated. Corrosion behaviour of the films in simulated biological fluid solution was evaluated by electrochemical impedance spectroscopy. It was found that both the Ta and TaN films enhanced corrosion resistance of the Ti6Al4V substrate with the best protective characteristics achieved by the TaN film deposited at 0.25 N2/Ar gas ratio. The protective characteristic was attributed to the formation of tantalum oxide and oxynitride compound at the surface, as verified by X-ray photoelectron spectroscopy. Increasing N2/Ar gas ratio increased susceptibility to localized corrosion. The corrosion resistance decreased as the thickness of the film increased to 1 μm.

Structure, phase evolution, and mechanical properties of DC, pulsed DC, and high power impulse magnetron sputtered Ta–N films

The microstructural development of reactively sputter-deposited tantalum nitride thin films is investigated as a function of the N2-to-total-pressure ratio (pN2/pT) and the operating mode of the metallic tantalum cathode; by direct current magnetron sputtering (DCMS), pulsed DCMS, and high power impulse magnetron sputtering (HiPIMS). For all sputtering modes investigated, the phase evolution of the Ta-N films strongly depends on the nitrogen partial pressure, pN2, used when keeping the total pressure, pT, constant at 0.3 or 0.6 Pa. The major crystalline phases identified, with increasing the pN2/pT-ratio, are α-Ta, orthorhombic o-Ta4N, hexagonal close packed (hcp) γ-Ta2N, face-centred cubic δ-TaN, and hcp ε-TaN. Their development is basically determined by the N2 partial pressure present. The deposition rate decreases slowest with increasing pN2 for the HiPIMS mode and fastest for the DCMS mode. The coatings with a dominating γ-Ta2N phase (which could be obtained for pN2 between 0.08 and 0.15 Pa) exhibit the highest hardness with 38.2 ± 4.6 GPa (HiPIMS), 38.0 ± 2.3 GPa (pulsed DCMS), and 40.0 ± 3.8 GPa (DCMS) among all samples studied. Higher pN2 lead to the formation of δ- and ε-TaN phases and a reduction in hardness. Especially, the ε-TaN rich coatings are comparably soft with only ~20 GPa.Based on our results we can conclude that coatings dominated by Ta-rich o-Ta4N or γ-Ta2N phases exhibit the most favourable mechanical properties, according to which the most important pN2-range is between 0.04 and 0.15 Pa, as for higher N2 partial pressures the films undergo a transformation from γ-Ta2N (plus o-Ta4N) into mixed δ- and ε-TaN.

Atomic layer deposition of amorphous Ni-Ta-N films for Cu diffusion barrier

Novel Ni-doped TaN (Ni-Ta-N) films are deposited by remote plasma-enhanced atomic layer deposition (ALD) with pentakis(dimethylamino)tantalum, nickelocene, and NH3 precursors for Cu diffusion barriers. Various Ni-Ta-N films with different compositions are achieved by changing the deposition cycles (n) of Ni sublayer while fixing the deposition cycles of TaN sublayer at 2. As n increases from 1 to 6, the root-mean-square roughness of the deposited film increases from 0.150 to 0.527 nm, and the resistivity decreases from 0.18 to 1.1 × 10−2 Ω cm. After annealing at 400 °C for 30 min in the forming gas (N2/H2), these films still maintain an amorphous texture and demonstrate a negligible reduction of resistivity and a weak increase of density. Subsequently, the barrier effects of the Ni-Ta-N films with different compositions are compared against Cu diffusion after annealing. The results reveal that the Ni-Ta-N films with n ≤ 4 exhibit barrier effects comparable with the ALD TaN film even after annealing at 550 °C. Further, a 3 nm ultrathin Ni-Ta-N film with n = 4, corresponding to an addition of ∼22 at. % Ni to TaN, cannot only reduce the film resistivity by 78% but also effectively block Cu diffusion after annealing at 450 °C for 30 min.