Thin Films Of Tantalum Nitride Research Articles

Degradation behaviors and failure of magnetron sputter deposited tantalum nitride

A reactive direct current magnetron sputtering method with a controlled total gas flow rate was used to fabricate thin films of tantalum nitride (TaN) on SiO2/Si and multilayer ceramic substrates. In order to identify the total gas flow rate that produced the lowest variation in the sheet resistance and the temperature coefficient of resistance (TCR), TaN films deposited under total gas flow rates of 30, 40, 60, and 80 sccm were characterized in terms of their structural and electrical properties. The optimum total gas flow rate was 60 sccm revealing the lowest deviation of sheet resistance and TCR. Next, the durability and reliability at high temperatures, after heating and cooling cycles, and exposure to induced current were tested. The degradation behaviors and failure of TaN films were investigated by measuring the sheet resistance variation. To further explain the degradation of TaN films, additional analysis of their crystallinity was conducted. The results showed that TaN-based thin film resistors have high durability and reliability and are suitable for embedded passive resistors.

Superconductor to weak-insulator transitions in disordered tantalum nitride films

We study the two-dimensional superconductor-insulator transition (SIT) in thin films of tantalum nitride. At zero magnetic field, films can be disorder-tuned across the SIT by adjusting thickness and film stoichiometry; insulating films exhibit classical hopping transport. Superconducting films exhibit a magnetic field-tuned SIT, whose insulating ground state at high field appears to be a quantum-corrected metal. Scaling behavior at the field-tuned SIT shows classical percolation critical exponents $z \nu \approx$ 1.3, with a corresponding critical field $H_c \ll H_{c2}$. The Hall effect shows a crossing point near $H_c$, but with a non-universal critical value $\rho_{xy}^c$ comparable to the normal state Hall resistivity. We propose that high-carrier density metals will always exhibit this pattern of behavior at the boundary between superconducting and (trivially) insulating ground states.

Phase map, composition and resistivity of reactively magnetron sputtered and annealed Ta–N films

Thin films of tantalum nitride (Ta–N) have been prepared by reactive magnetron deposition under various nitrogen partial pressures and subsequently annealed (Ta = 450–950 °C). The structure, density, composition and electrical resistivity of the prepared films were systematically investigated. A phase map was constructed from the results of structural analysis. With increasing of from 0 to 0.2, a single-phase or two-phase mixture films of tetragonal Ta, Ta2N ( °C), ϵ-TaN ( °C), θ-TaN ( °C) and fcc δ-TaN are sequentially observed. For –0.45, the as grown and annealed films exhibit δ-TaN structure. Amorphous films grown in the –0.75 range crystallize as cubic Ta2N3 upon annealing at °C or as δ-TaN at °C. A cubic Ta2N3 is grown at highest (0.85), which decomposes to δ-TaN at °C. The N / Ta atomic ratio in the film linearly increases for –0.5, ranging from 0 to 2.1, while the mass density monotonically decreases with . Upon annealing, a part of N atoms out-diffuses from the films deposited at . The electrical resistivity strongly depends on both and Ta. However, in the as grown and annealed δ-TaN films the resistivity was of the order of 100–1000 cm. In these films, a correlation between the resistivity and the average number of defects (Ta vacancies and N atom excess) is observed. Finally, the influence of thermally introduced oxygen on the films resistivity has been revealed.

Deposition of tantalum nitride thin films by D.C. magnetron sputtering

Thin films of tantalum nitride (TaN) were deposited on SKD11 tool steel substrate by a D.C. magnetron sputtering system. The influence of the N2/Ar gas ratio of the inlet gases on the structure, hardness, adhesion and wear resistance was investigated. The X-ray diffraction data showed that TaN deposited at low N2/Ar gas ratio, tetragonal β-Ta(330) and hexagonal TaN(101) were observed. Orthorhombic TaN(110) and orthorhombic Ta3N5 were formed with the increase of the N2/Ar gas ratio. High hardness of the films was observed at the low N2/Ar gas ratio. The films deposited at N2/Ar gas ratio of 0.3 showed good adhesion, wear resistance and hardness of Hv0.05 1450. The films deposited with etching time of 30 min at 133.32 Pa gave good adhesion. Thickness of the films decreased with applying the bias voltage. As the bias potential was increased, the hardness of the film increased and then decreased. The films with fine dome structure showed good wear resistance.

The impact of layer thickness of IMP-deposited tantalum nitride films on integrity of Cu/TaN/SiO 2/Si multilayer structure

This work concentrates on the diffusion barrier stability of very thin tantalum nitride films with different thickness (10, 20 and 30 nm) sputter-deposited on silicon dioxide in the Cu/TaN/SiO 2/Si multiplayer structure. The impact of varying layer thickness and influence of post deposition annealing on the crystal structure, resistivity, intermixing and reactions at the interfaces were studied by using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry. The results revealed that the thinner the film thickness of tantalum nitride, the more severe the reactions at the interface of copper–tantalum nitride and consumed more conductive Cu. Accelerated grain growth and/or agglomerations were also observed in all Cu surfaces. All the structures show a similar degradation process and were found to be stable up to 450°C for 35 min.

Low-pressure chemical vapor deposition of TaCN films by pyrolysis of ethylamido-tantalum

Thin films of Tantalum nitride (TaN) were deposited from tetra-ethylamido-tantalum (Ta (NEt 2) 4) by low-pressure chemical vapor deposition. Good-quality step coverage is achieved below 400°C, because the deposition rate is determined by the reaction rates on the surface. The film resistivity increases, however, as the substrate temperature decreases. In order to obtain the low resistivity of films deposited at lower temperatures, we have increased the amount of injected H 2 gas during the deposition. The resistivity decreases by the increase in the H 2 gas flow rate, and it is shown that a large amount of H 2 gas injection during the deposition is an effective method for obtaining both low resistivity and high-quality step coverage. The residual carbon concentration in the film is measured to be >10%, on the other hand, the concentration of N less than 1%. The microstructural investigation using transmission electron microscopy (TEM) reveals that crystalline structure of the deposited film has an amorphous phase.

Substrate composition effects on the interfacial fracture of tantalum nitride films

In this study we combined nanoscratch testing with a multilayer sapphire and aluminum nitride single-substrate system to determine the effects of interface composition and structure on susceptibility to fracture of hard, thin tantalum nitride films. Nanoindentation tests showed that the elastic moduli of the tantalum nitride and aluminum nitride films, as well as the sapphire substrate, were essentially equal at 400 GPa. On both portions of the substrate, these tests also showed that near surface hardness was near 35 GPa. Nanoscratch tests triggered long blisters and circular spalls on both the sapphire and aluminum nitride portions of the substrate. The blisters showed that the tantalum nitride film was subjected to a compressive residual stress of −6.7 GPa. The spalls showed that failure occurred along the tantalum nitride film-substrate interface regardless of substrate composition. Most importantly, the blisters and spalls showed that the mode I componentof the fracture energies was essentially equal on both substrate materials at a value near 3.1 J/m2. These energies are on the order of the energies for metallic bonding.

Remote Plasma-Assisted Metal Organic Chemical Vapor Deposition of Tantalum Nitride Thin Films with Different Radicals

Thin films of tantalum nitride have been deposited from remote plasma-assisted metal organic chemical vapor deposition (RP-MOCVD) using the reaction of pentakis-dimethyl-amino-tantalum (PDMATa) with different activated radicals. Microstructures of deposited films measured by X-ray diffraction (XRD) and transmission electron microscopy (TEM) depend on the deposition temperature and the type of radicals. At temperatures below 300°C, amorphous films are obtained which are independent of the reacting species. On the other hand, at higher deposition temperatures, (111)-preferred cubic TaN films are obtained when they react with ammonia plasma, while the reaction with hydrogen plasma produces amorphous films. All amorphous films obtained are recrystallized at an annealing temperature of 1000°C in an oxygen-containing (10%) ambient, showing (111) TaN, bcc Ta, and signals of orthorhombic Ta2O5. From detailed studies of film composition and chemical bonding in the obtained films, the impurity incorporation, especially carbon, is responsible for the dependence of film microstructures on different deposition conditions.

Interface Structure Effects on the Fracture of Hard Thin Films

In this study we combined nanoscratch testing with a multi-layer aluminum oxide and aluminum nitride single substrate system to determine the effects of interface composition and structure on susceptibility to fracture of hard, thin tantalum nitride films. Nanoscratch tests showed that the film on aluminum oxide and on aluminum nitride portions of the substrate failed readily along the tantalum nitride film-substrate interface regardless of substrate composition. Most importantly, the fracture energies were essentially equal on both substrate materials. These results strongly suggest that a sputter deposited interface structure controls susceptibility to fracture.

Residual Stress Effects on the Fracture of Tantalum Nitride Films

ABSTRACTIn this study, continuous microscratch testing was used to determine the effects of compressive residual stresses on the fracture of thin tantalum nitride films. The films were sputter deposited at room temperature onto single crystal sapphire substrates to a thickness of 600 nm. Some films were left in the as-deposited condition while the remaining films were vacuum annealed at 300°C. The only discernible change in structure was a surface rearrangement of atoms into parallel arrays of striations on the vacuum annealed samples revealing a high compressive residual stress in the films. These stresses had a strong effect on fracture as shown by the as-deposited films which buckled readily during scratch tests forming uniform-width and circular blisters while the vacuum annealed films exhibited a much lower susceptibility to fracture. Application of mechanics-based models for film buckling defined the levels of compressive residual stress and their effect on interfacial fracture.

Hydrogen Effects on the Fracture of Thin Tantalum Nitride Films

AbstractIn this study we used nanoindentation and continuous microscratch testing to determine the effect of hydrogen on the work of adhesion and fracture toughness of thin tantalum nitride films. These films were sputter-deposited on sapphire substrates to a thickness of 600 nm followed by the heating of some films in deuterium and some in vacuum at 300°C. Deuterium was used in this study because it is much easier to detect and measure than hydrogen. Ion beam spectroscopy showed that exposure to deuterium produced a uniform internal deuterium concentration of 2000 appm. Nanoindentation showed that exposure to deuterium at 300°C and vacuum annealing at 300°C had little effect on elastic modulus and hardness values of these films at room temperature. In contrast, the microscratch tests at room temperature revealed that the work of adhesion decreased from 24.5 J/m2 after vacuum annealing to 9.1 J/m2 after deuterium charging and demonstrated that tantalum nitride films have a strong susceptibility to hydrogen embrittlement.

The Effects of High Temperature Exposure on the Fracture of Thin Tantalum Nitride Films

ABSTRACTContinuous microscratch testing was used in this study to determine the effects of elevated temperature exposure on the adhesion and toughness of thin tantalum nitride films. These films were sputter-deposited at room temperature on sapphire substrates to a nominal thickness of 600 nm with some films heated to 600°C in vacuum while others were heated to 600°C in air. The films heated in vacuum exhibited no changes in composition or structure while the films heated in air completely transformed to tantalum pentoxide. Comparison of the results shows that the interfacial fracture toughness increases from 0.5 MPa-m1/2 for as-sputtered films to 0.8 MPa-m1/2 for films heated in air. However, the toughness increases to more than 3.0 MPa-m1/2 when the films are heated in vacuum. The increase in toughness values follows the reduction in deposition defect content where formation of an oxygen deficient tantalum oxide layer in air from the as-sputtered film increases interfacial toughness slightly while full densification of the tantalum nitride films in vacuum increases toughness to very high levels.

Properties of anodic oxide films prepared on nitrogen-doped tantalum films

Capacitors prepared from thin films of tantalum nitride, which has an h.c.p. structure, show various excellent electrical properties. TaN capacitors, in particular, exhibit great endurance to heat treatment and have no polarity in their anodic and cathodic leakage currents. The structure of these anodic films, their dielectric properties and their electrical conduction characteristics were studied. An anodic film formed on a nitrogen-doped tantalum film was shown to consist of two layers by analysis using the chemical etching method and by Auger electron spectroscopy. The first layer, which is situated at the oxide-electrolyte interface, has a high density and includes very little nitrogen. The second layer is porous and contains excess nitrogen.

Glow discharge mass spectrometry of sputtered tantalum nitride

It is well known that the properties of reactively sputtered thin films of tantalum nitride are dependent upon the partial pressure of N2 in the sputtering gas. In this study, a Ta target was rf diode sputtered using various Ar/N2 gas mixtures. Glow discharge spectrometry was used to monitor the positive ions present in the sputtering plasma. Electrical and x-ray diffraction measurements on the resulting films related their crystallography and resistivity to the composition of the plasma, in particular to the relative number of Ta and TaN ions. The results are discussed in terms of the change in the target surface with increasing N2 partial pressure.