IronIII for TiIV substitution in the structure of pedogenic and synthetic anatase of up to Fe/ (Ti+Fe) 0.1 mol/mol was indicated by an increase in unit cell size as measured by XRD line shifts. Mössbauer- and electron paramagnetic resonance spectra at both, 298 K and 4.2 K supported this by the presence of signals typical for octahedrally coordinated FeIII in a diamagnetic matrix. Charge compensation was achieved by structural OH, as indicated by FTIR bands at 3360 and 960 cm−1, which were absent in pure anatase and which disappeared on heating. The weight loss on heating amounted to ca. 0.5 mol H2O/mol Fe. At 600°C structural Fe was ejected, the unit cell size decreased to that of pure anatase, and pseudobrookite, Fe2TiO5, was formed.

Microwave plasma chemical vapor deposition (MPCVD) was used to diffuse boron into tantalum using plasma initiated from a feedgas mixture containing hydrogen and diborane. The role of substrate temperature and substrate bias in influencing surface chemical structure and hardness was investigated. X-ray diffraction shows that increased temperature results in increased TaB2 formation (relative to TaB) along with increased strain in the tantalum body-centered cubic lattice. Once the strained tantalum becomes locally supersaturated with boron, TaB and TaB2 precipitate. Additional boron remains in a solid solution within the tantalum. The combination of precipitation and solid solution hardening along with boron-induced lattice strain may help explain the 40 GPa average hardness measured by nanoindentation. Application of negative substrate bias did not further increase the hardness, possibly due to etching from increased ion bombardment. These results show that MPCVD is a viable method for synthesis of superhard borides based on plasma-assisted diffusion.

Mechanism for the hardening of two-phase Ni3Al-Ni3V intermetallic alloy to which 2 at.% Ta was added in different substitution manners for Ni, Al and V was presented, based on the microstructural observation, alloying behavior and lattice properties of the additive in the constituent phases. The hardening behavior was explained in terms of solid solution hardening in which the mixture rule in the volume fraction of the two constituent phases and the atomic size misfit evaluated from the changes of the lattice parameters were incorporated. Consequently, the hardening for the alloys in which the additives were substituted for Ni and V was attributed to solid solution hardening. On the other hand, the hardening for the alloy in which the additive was substituted for Al was attributed to the hardening due to microstructural refining in addition to the solid solution hardening.

Thermal stability of pulsed laser deposited (PLD) nanocrystalline tantalum was explored through in situ transmission electron microscopy (TEM) annealing over the temperature range of 800–1200 °C. The evolution of the nanostructure was characterized using grain size distributions collectively with electron diffraction analysis and electron energy loss spectroscopy (EELS). Grain growth dynamics were further explored through molecular dynamics (MD) simulations of columnar tantalum nanostructures. The as-deposited grain size of 32 nm increased by only 18% at 1200 °C, i.e., 40% the melting point of tantalum, conflicting with the MD simulations that demonstrated extensive grain coalescence above 1000 °C. Furthermore, the grain size remained stable through the reversible α-to-β phase transition near 800 °C, which is often accompanied by grain growth in nanostructured tantalum. The EELS analysis confirmed the presence of oxygen impurities in the as-deposited films, indicating that impurity stabilization of grain boundaries was responsible for the exceptional thermal stability of PLD nanocrystalline tantalum.

A synthetic cubic pyrochlore, Gd2Ti2O7 (Fd3̅m) irradiated with swift heavy ions is compared with a compositionally-related composition La2Ti2O7 (P21), which has a monoclinic, layered, perovskite-type structure. Irradiation experiments were performed at the GSI Helmholtz Center with 181Ta ions and 129Xe ions at specific energies of 11MeV/amu. At these energies the ions pass entirely through the sample thickness of ∼ 40 μm. Angle-dispersive synchrotron powder x-ray diffraction (XRD) measurements were completed and an increasing ion-induced amorphization with increasing ion fluence was for both phases. The ion track cross-sections for the radiation-induced crystalline-to-amorphous transformation, as determined from the evolution of the integrated peak intensities as a function of fluence, reveal that La2Ti2O7 (track diameter, d ∼ 7.2 nm with 181Ta and 5.1 nm with 129Xe) is more susceptible to amorphization than Gd2Ti2O7 (d ∼ 6.2 nm with 181Ta and 4.6 nm with 129Xe). The radiation response of the two titanate compounds can be understood in the context of their different structures and cation ionic radius ratios rA/rB, where the susceptibility of radiation of titanate pyrochlores is proportionate with this radius ratio. The higher electronic linear energy loss of the 181Ta ions as compared with 129Xe ions leads to a consistent increase of volume amorphized per ion in both materials, which manifests as a larger track diameter.

Metallic nanoparticles under 10 nm are of particular interest for the microelectronics industry. However, there is a lack of convenient synthetic routes to control their size Oxophilic metals, such as Ta, are also of high interest, however, the high oxophilicity and melting point makes the synthesis of such nanoparticles challenging. Making use of imidazolium-based ionic liquids, monodisperse zero-valent tantalum nanoparticles (Ta(0)NPs) have been successfully synthesised at room temperature by reduction of tris(neopentyl)neopentylidenetantalum(V). Furthermore; well size-controlled bimetallic Ru-Ta NPs have also been synthesized.

Ta doped SnO2 (TTO) films prepared on quartz glass substrates at 200 °C were annealed in the air to investigate the annealing effect on the structural, the optical, and the electrical properties. It is shown that the annealing for TTO films resulted in beneficial effect on the electrical resistivity by improving the carrier density and Hall mobility. The lowest resistivity was 1.4 × 10-3Ω cm obtained at 400 °C annealing temperature. The scattering mechanism in TTO films was discussed from the optical and electrical perspectives. The variation in Hall mobility with increasing the annealing temperature may be attributed to the scattering from the ionized and neutral impurities in TTO films.

Oxidation-induced stress evolutions in Ta thin films were investigated using ex situ microstructure analyses and in situ wafer curvature measurements. It was revealed that Ta thin films are oxidized to a crystalline TaO2 layer, which is subsequently oxidized to an amorphous tantalum pentoxide (a-Ta2O5) layer. Initial layered oxidation from Ta to TaO2 phases abruptly induces high compressive stress up to about 3.5 GPa with fast diffusion of oxygen through the Ta layer. Subsequently, it is followed by stress relaxation with the oxidation time, which is related to the slow oxidation from TaO2 to Ta2O5 phases. The initial compressive stress originates from the molar volume expansion during the layered formation of TaO2 from the Ta layer, while the relaxation of the compressive stresses is ascribed to the amorphous character of the a-Ta2O5 layer. According to Kissinger's analysis of the stress evolution during an isochronic heating process, the oxygen diffusion process through the a-Ta2O5 layer is the rate-controlling stage in the layered oxidation process of forming a a-Ta2O5/TaO2/Ta multilayer and has an activation energy of about 190.8 kJ/mol.

The scaling of BEOL interconnect technology in ULSI circuitry requires the integration of Cu wiring with ultra-low K (ULK) dielectrics. We present the results of a study of the interaction between different-stoichiometry Ta(N)/Cu barrier processes and porous ULK dielectrics (k=2.4) at 32nm groundrules Auger and diffraction analysis of blanket wafers was used to benchmark two different stoichiometries of TaN barrier deposited using commercially-available ionized PVD sources. Comparison TEM and EDX/EELS images indicates that barrier oxidation is occurring in the low nitrogen-content Ta(N) barrier, which is absent at the higher stoichiometry. These differences are further manifested in defect-density analysis of patterned wafers comparing the two processes. These results illustrate the critical importance the TaN barrier properties play in enabling the integration of Cu/ULK interconnects at 32nm at beyond.

Recently the Flash Memory is scaling limit, Thus the Memory of various types is now under study for the next generation large capacity nonvolatile memory. Resistance random access memory (ReRAM) is attracts much attention due to its advantage for integration in the next generation nonvolatile memory, because it is depend on scaling by lithography compared with the Flash Memory of capacity type. The material for ReRAM is classified roughly into binary oxides and perovskite oxides. Several binary oxides such as a TaOx have the advantage for low-temperature process and low-cost materials compared with perovskite oxides such as a (Pr,Ca)MnO3 (PCMO). In this study, TaOx film with the thickness of 10nm were prepared by reactive RF magnetron sputtering on 8inch-Pt/Si substrate using a Ta metal target in oxygen ambient. The sputtering system was the multi chamber type mass production tool. The TaOx thin film was amorphous phase as a result of measurement by X-ray diffraction meter. Ta top electrodes with 50 um diameters were deposited on the surface of TaOx layer by the DC sputtering method using a shadow mask. The “Forming” voltage of TaOx-ReRAM was 5.0V. After “Forming” process, the “Set” and “Reset” voltage were 3.0V and –3.0V respectively. It has good switching properties with large on/off resistance ratio above 1,000.

A novel end-point detection method based on a combination of shear force and its spectral amplitude was proposed for barrier metal polishing on copper damascene structures. Under some polishing conditions, the shear force changed significantly with polished substrate. On the other hand, the change in shear force was insignificant under certain polishing conditions. Therefore, a complementary end-point detection method by monitoring oscillation frequency of shear force was proposed. It was found that the shear force fluctuated in unique frequencies depending on polished substrates. Using Fast Fourier Transformation, the shear force data was converted from time domain to frequency domain. The amplitude of spectral frequencies corresponding to the rotational rate of wafer carrier and platen was monitored. Significant frequency amplitude changes were observed before, during and after the polished layer transition from barrier film to silicon dioxide film. The results indicated that a combination of shear force and its spectral amplitude analyses provided effective end-point detection for barrier CMP process.

The effect of microstructural inhomogeneities with different length scale on the plasticity of (Ti45Zr16Be20Cu10Ni9)100–xTax (x = 0, 5, and 10) bulk glassy alloys has been studied. The formation of specific heterogeneous microstructures with a different type of structural inhomogeneity, i.e., short-/medium-range ordered clusters or micrometer-scale ductile dendrites combined with a glassy matrix, evolved by appropriately tuning the alloy chemistry, improves the room temperature plasticity up to ∼12.5% and ∼15%, respectively. The pronouncedly enhanced plasticity is mainly attributed to the retardation of shear localization and multiplication of shear bands by controlling the plastic and failure instabilities otherwise responsible for premature failure.

TaCN-based metal films were grown by metal-organic chemical-vapor deposition (MOCVD) and atomic vapor-deposition (AVD). Thermal decomposition at 500ºC leads to com-positions of approximately Ta0.50C0.4N0.1 (“TaCN”), whereas a reactive process using NH3 leads to the formation of Ta0.65C0.1N0.25 (“Ta2N”) films. All films are nearly amorphous as grown and recrystallize only weakly after spike annealing at 1050°C. The thermal stability of TaCN/HfSiO4 and Ta2N/HfSiO4 stacks during spike annealing at 1050°C was studied and Si and Hf outdiffusion into TaCN or Ta2N was observed. The effective work functions of TaCN and Ta2N on HfSiO4 were found to be as high as 4.9 eV after high thermal budget. It is demonstrated that the effective work function can be further increased to 5.1 eV after high thermal budget by the insertion of a thin Al2O3 capping layer between HfSiO4 and the metal films.

Establishing a cost-effective technology for the metallization of through-Si vias (TSV) is an important factor in the realization and volume manufacturing of 3D-stacked integrated circuits (3D-SIC). Cu electroplating, which is the preferred technique, should provide not only a void-free TSV fill, but also short filling time and small overburden. The duration of the plating process is a significant contributor to the overall 3D process cost, and thus needs to be minimized. The overburden, the thickness of the material deposited on the top surface of the wafer, has to be limited for compatibility with the following processing steps (e.g. chemical mechanical polishing, CMP). In this paper we report on Cu plating of TSV-s with a thin Ta film on the field. The thin Ta film is sputtered on top of the Ta barrier/Cu seed, and inhibits Cu plating outside the TSV-s. We show that the use of this Ta-cap and in situ electrochemical monitoring techniques leads to significant savings in plating and polishing time, and thus savings in manufacturing costs of 3D-stacked integrated circuits.

The properties of Ta2O5 thin films with respect to different underlayer stack have been investigated. At first, a set of samples were produced at various conditions as an underlayer of Ta2O5 film deposition. Then, Ta2O5 films were grown using a MOCVD method with Ta(OC2H5)5 pre-curser at 440 °C. The Process parameters for Ta2O5 films were remained same through the preparation of the sample set. The results were analyzed using various methods including thickness measurement, SEM, stress measurement, X-ray diffraction (XRD), and electrical property measurements. Different grain structures and growth rates were observed with respect to the different underlayer preparation condition mainly as a function of deposition temperature. The deposition rate varied from 0.6 Åsec to 1.8Åsec depend on different underlayer. Crystalline Ta2O5 films with large-grain-size were obtained on Aluminum/TiN underlayer stack. Films with crystalline structure show better leakage current characteristics than the amorphous one.

In Copper back-end-of-line (BEOL), the “punchthru™ process” – removal of barrier material from via bottom during etch/re-sputter step, and gouging into the underlying Copper line - has been increasingly used in 65nm production for its superior reliability. However, with the adoption of porous low-k dielectric at 45nm node and beyond, the conventional punchthru process can cause physical damage to the porous dielectric, such as roughening of the trench bottom in dual damascene structures, micro-trenching in the bottom of single trenches, which may have reliability implications. This paper reported on the use of off-angular Tantalum neutral flux during the re-sputter process to improve the selectivity between the via and trench bottom in order to protect the trench bottom and via bevel, while still allowing sufficient gouging into the underlying Copper line. In addition, the plasma density and ion energy are adjusted to further optimize selectivity, and to eliminate any micro-trenching. Therefore, this paper demonstrated PVD high deposit/etch selectivity process based on transmission-electron microscopy (TEM) and studies of electrical test result. This approach has extended the PVD Tantalum barrier process to at least 32nm node.

A thermogravimetric method was used to analyze intermediate processes involved in the formation and decomposition of AgNbO3and AgTaO3perovskites. Critical parameters that control the kinetics of the formation are associated with oxygen transport. The Nb2O5crystal structure has a capacity to trap molecular oxygen, which evolves during the decomposition of Ag2O that is present in a starting mixture. The formation of the perovskite phase involves a simultaneous reaction of three species: O2, Ag, and Nb2O5/Ta2O5. As the trapped molecular oxygen is in the immediate vicinity of the reaction site, the kinetics of the reaction is significantly accelerated. An absence of the molecular oxygen in the solid-state phase cannot be compensated for with an increase in a partial pressure of oxygen in the gas phase, that is, application of oxygen atmosphere.

In this study, a novel method is explored for improving the electromigration lifetime of Cu wires, using Ta implantation into Cu. For high implant doses (2E15 cm−2), the electromigration lifetime is improved by over 5X using this method. An increase in lifetime is achieved, even for an average surface concentration of Ta on the order of 0.1 atm%. We propose that the improvement in electromigration lifetime is due to the reduction of defects at the SiN/Cu interface due to the presence of Ta. The line-to-line leakage at high voltages (> 5V) increases with the Ta implant, with higher leakage at higher Ta concentrations, so the Ta dose must be limited to avoid excessive leakage.

We have investigated the effect that the Ta content has on the ferroelectric properties of strontium bismuth tantalate (SBT) thin films synthesized using metalorganic decomposition (MOD) and spin coating techniques. The physical properties of these SBT samples were strongly dependent upon the Ta ratio. Polarization measurements revealed that Ta-deficient SBT exhibited a relatively low coercive field (2Ec ∼ 87 kV/cm) and a high remanent polarization (2Pr ∼ 15 μC/cm2). The value of 2Pr decreased as the Ta ratio in SBT increased. The improved ferroelectric properties of the Ta-deficient SBT samples may have resulted from the uniformly well-grown bismuth-layered-structured (BLS) phases of the films and their highly preferential orientation along the a and b axes. We suggest that the incorporation of Ta vacancies plays an important role in enhancing the crystallinities and microstructures of Ta-deficient SBT films.

Ceramics in the system ZrB2–Ta5Si3 were studied as candidates for the development of new ultra high-temperature ceramic materials. The ceramics were prepared by hot pressing at 1900–2200 °C in He. Mutual additions of ZrB2 and Ta5Si3 even in small amounts had significant densifying effects due to chemical interactions and solid solubility between the components, which have not been reported in the literature. Materials containing between 8 and 30 vol% Ta5Si3 exhibited less oxidation than pure ZrB2, which is the result of phase separation in surface borosilicate glass induced by Ta2O5. For higher concentrations, oxidation resistance substantially decreased with increasing Ta5Si3 content. The trend in the oxidation behavior of the materials showed significant dependence on the volume of oxidation products. Ceramics containing up to 10 mol% (30 vol%) Ta5Si3, which showed the highest oxidation resistance, also had the highest strength and hardness in the system, and are of interest for high-temperature structural applications in oxidizing environments.