Preparation and characterization of sputtered Cu films containing insoluble Nb

Copper films containing various amounts of insoluble Nb (up to 24.7 at.%) were prepared by r.f. magnetron sputtering. The crystallography and microstructure of the films were investigated for as-deposited and annealed Cu(Nb) thin films. Cu(Nb) thin films are found to consist of non-equilibrium supersaturated solid solution of Nb in Cu with a nanocrystalline microstructure. X-ray diffraction and scanning electron microscope analyses revealed a reduction in the grain sizes of the films with increasing Nb content in the films leading to a grain refinement. The electrical resistivity of as-deposited and annealed Cu(Nb) thin films is found to be low for an Nb content 2.7 at.%. Significant drops in the resistivity were observed for the high Nb contents after annealing at 530 °C which may be due to grain growth and formation of Nb-bearing phase in the film. Microhardness of the films was found to increase with the Nb concentration due to the combined effects of grain refinement and the solute strengthening of Nb.     

Diffusion barrier capability of Zr-Si films for copper metallization with different substrate bias voltage

Efficiency of Zr-Si diffusion barriers in Cu metallization has been investigated. Amorphous Zr-Si diffusion barriers were deposited on the Si substrates by reactive magnetron sputtering with different negative substrate bias. The mass density of Zr-Si films increases with substrate bias voltage up to − 150 V. The deposition rate decreased with the negative substrate bias from 5.4 nm/min to 1.8 nm/min. XRD measurements show that the Zr-Si barriers have amorphous structure in the as-deposited state. The FE-SEM images show that the sizes of spherical granules on the Zr-Si film surface increase with increasing the substrate bias. The Cu/Zr-Si/Si structures were prepared and annealed in Ar ambient at temperatures varying from 500 to 650 °C for an hour. It is shown from the comparison study that the Zr-Si film deposited with − 150 V is better at maintaining good performance in Cu/Zr-Si/Si contact system than that of Zr-Si film deposited with − 50 V.     

Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films

We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other.     

Power and pressure effects upon magnetron sputtered aluminum doped ZnO films properties

In this work, polycrystalline aluminum doped zinc oxide (ZnO:Al) films with c-axis (002) orientation have been grown on glass and silicon substrates by RF (radio frequency) magnetron sputtering technique, at room temperature. A systematic study of the effect of sputtering deposition parameters (i.e. RF power and argon gas pressure) on the structural, optical and electrical properties of the films was carried out. We observed that, with increasing RF power the growth rate increased, while it decreased with increasing gas pressure. As mentioned above, the films were polycrystalline in nature with a strong preferred (002) orientation. The intrinsic compressive stress was found to decrease with both increasing RF power and gas pressure, and near stress-free film was obtained at 200 W RF power and 2 × 10^− 1 Pa gas pressure. The obtained ZnO:Al films, not only have an average transmittance greater than 90% in the visible region, but also have an optical band gap between 3.33 and 3.47 eV depending on the sputtering parameters. Moreover, a low value of the electrical resistivity (~ 1.25 × 10^− 3 Ω cm) was obtained for the film deposited at 200 W and 2 × 10^− 3 mbar.     

Influence of substrate direct current bias voltage on microcrystalline silicon growth during radio-frequency magnetron sputtering

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared on glass, aluminum-covered glass and Si wafer substrates at various substrate bias voltages (V_sb) between -400 and +50 V, and the influence of V_sb on their structural properties was investigated. The crystallinity (crystalline volume fraction and crystallite size) of the μc-Si:H films deposited on glass remained unchanged with respect to V_sb. For μc-Si:H films deposited on aluminum within the V_sb range of -20 to +50 V, the crystallinity also remained unchanged and showed the same crystallinity as that of the films deposited on glass substrate. However, the crystallinity of the μc-Si:H films deposited on aluminum-covered substrate was reduced as V_sb decreased from -20 to -100 V, and the film at V_sb=-400 V was completely amorphous.     

Bias effect on microstructure and mechanical properties of magnetron sputtered nanocrystalline titanium carbide thin films

Nanocrystalline titanium carbide (TiC) thin films were prepared by magnetron sputtering deposition at 473 K. The effect of substrate bias on microstructure and mechanical properties was studied in details using X-ray photoelectron spectroscopy, X-ray diffraction, field emission scanning electron microscopy, indentation and scanning microscratch. The TiC films exhibit a (111) preferential orientation. Substrate bias decreases grain size and deposition rate of the TiC films. The TiC films have columnar structure which becomes finer at high substrate bias. Nanoindentation hardness, Young's modulus, and toughness of the films are increased as the substrate bias goes up. However, the adhesion peaks at substrate bias of − 100 V and drops when bias is increased further.     

Strain effects on annealing behaviours of moderately deformed nanocrystalline nickel

Abstract

We report the annealing behaviours of nanocrystalline nickel as a function of plastic strain. A broad exothermic reaction due to primary and secondary recrystallisations appears in moderately deformed samples that are enhanced by plastic strain. Texture analysis shows that predeformation and recrystallisation play an important role in grain orientation. A certain difference in texture evolution exists in samples predeformed to different strains. Defects such as stacking faults and twinning should be considered to pin down the underlying mechanisms. The final grain orientation indicates that twinning plays an important role in grain growth due to orientation selection.     

Effect of deposition angle on the structure and properties of pulsed-DC magnetron sputtered TiAlN thin films

This article reports the comparison of structure and properties of titanium aluminum nitride (TiAlN) films deposited onto Si(100) substrates under normal and oblique angle depositions using pulsed-DC magnetron sputtering. The substrate temperature was set at room temperature, 400 °C and 650 °C, and the bias was kept at 0, − 25, − 50, and − 80 V for both deposition angles. The surface and cross-section of the films were observed by scanning electron microscopy. It was found that as the deposition temperature increases, films deposited under normal incidence exhibit distinct faceted crystallites, whereas oblique angle deposited (OAD) films develop a kind of “tiles of a roof” or “stepwise structure”, with no facetted crystallites. The OAD films showed an inclined columnar structure, with columns tilting in the direction of the incident flux. As the substrate temperature was increased, the tilting of columns nearly approached the substrate normal. Both hardness and Young's modulus decreases when the flux angle was changed from α = 0° to 45° as measured by nanoindentation. This was attributed to the voids formed due to the shadowing effect. The crystallographic properties of these coatings were studied by θ-2θ scan and pole figure X-ray diffraction. Films deposited at α = 0° showed a mixed (111) and (200) out-of-plane orientation with random in-plane alignment. On the other hand, films deposited at α = 45° revealed an inclined texture with (111) orientation moving towards the incident flux direction and the (200) orientation approaching the substrate normal, showing substantial in-plane alignment.     

X-ray diffraction study of thermal stress relaxation in ZnO films deposited by magnetron sputtering

X-ray diffraction stress analyses have been performed on two different thin films deposited onto silicon substrate: ZnO and ZnO encapsulated into Si₃N₄ layers. We showed that both as-deposited ZnO films are in a high compressive stress state. In situ X-ray diffraction measurements inside a furnace revealed a relaxation of the as-grown stresses at temperatures which vary with the atmosphere in the furnace and change with Si₃N₄ encapsulation. The observations show that Si₃N₄ films lying on both sides of the ZnO film play an important role in the mechanisms responsible for the stress relaxation during heat treatment. The different temperatures observed for relaxation in ambient and argon atmospheres suggest that the thermally activated stress relaxation may be attributed to a variation of the stoichiometry of the ZnO films. The present observations pave the way to fine tuning of the residual stresses through thermal treatment parameters.     

Effects of thermal annealing on the semi-insulating properties of radio frequency magnetron sputtering-produced germanate thin films

We report the effects of thermal annealing on the semi-insulating properties of germanate thin films produced by a radio frequency magnetron sputtering process. Electrical and physical characterizations are presented. In the case of PbO-GeO₂ films (annealed and not annealed), the electron diffraction analysis from transmission electron microscopy has shown that the amorphous structure predominates, whereas the annealed PbO-GeO₂-AgNO₃ (1 wt.%) films presented crystalline nanoparticles in the range of 1 to 9 nm composed of Pb, PbO and Ag₄GeO₄. Also, not annealed and annealed films were used to produce metal-insulator-semiconductor structures. The electrical properties of these structures were analysed from capacitance-voltage and conductance-voltage characteristics. The results showed that the significant leakage current in the accumulation region in the not annealed films can be increased by the annealing process. In addition, stable semi-insulating layers with an almost constant shifting of the capacitance-voltage characteristics are obtained when annealed PbO-GeO₂-AgNO₃ (1 wt.%) films are employed. Based on a proposed model accounting for the leakage process, the influence of this leakage on the accumulation capacitance was also established. In addition, the decrease of the dielectric constant in the presence of crystalline nanoparticles was shown. The results obtained indicate that the germanate thin films are potential passivating materials for power device applications.     

Effect of the oxygen partial pressure on the microstructure and optical properties of ZnO:Cu films

Cu-doped zinc oxide (ZnO:Cu) films were deposited on Si substrates using radio frequency reactive magnetron sputtering at different oxygen partial pressures. The effect of oxygen partial pressure on the microstructures and optical properties of ZnO:Cu thin films were systematically investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and fluorescence spectrophotometer. The results indicated that the grain orientation of the films was promoted by appropriate oxygen partial pressures. And with increasing oxygen partial pressure, the compressive stress of the films increased first and then decreased. The photoluminescence (PL) of the samples were measured at room temperature. A violet peak, two blue peaks and a green peak were observed from the PL spectra of the four samples. The origin of these emissions was discussed and the mechanism of violet emission of ZnO:Cu thin films were suggested.     

Effects of low temperature on the characteristics of tantalum thin films

In this paper the effects of substrate temperature (room temperature - 350 °C) on the phase composition and crystallization orientation of the tantalum thin film deposited by direct current magnetron sputtering in an extremely low power deposition regime are presented. In this experiment, heating the substrates to 350 °C resulted in the growth of the hard and brittle tetragonal crystalline structure (β-Ta). Deposited tantalum has a conical structure with large voided boundaries. Sheet resistance of samples is much larger than for the convenient conductors which decreased with increasing the substrate temperature.     

Microstructure,grain growth,and hardness during annealing of nanocrystalline Cu powders synthesized via high energy mechanical milling

In this paper, the microstructure and hardness evolutions of commercially pure Cu subjected to high energy mechanical milling and subsequent annealing treatments in the temperature range of 400–700 °C are investigated. The results demonstrated the simultaneous occurrence of recovery, recrystallization, and grain growth during annealing of the nanocrystalline Cu. The volume fraction of the recrystallized grains estimated using the grain orientation spread exhibits lower values as a result of its dynamic recovery at higher temperatures. The normal grain growth in the range of 400–600 °C and significant abnormal grain growth at higher temperatures are observed during annealing. As a result of the abnormal grain growth, the microhardness value rapidly decreases for the sample annealed at 700 °C. An analysis of the grain growth kinetics using the parabolic equation in the temperature range of 400–600 °C reveals a time exponent of n ≈ 2.7 and an activation energy of 72.93 kJ/mol. The calculated activation energy for the grain growth in the nanocrystalline Cu is slightly less than the activation energy required for the lattice diffusion. This low activation energy results from the high microstrain as well as the Zener-pinning mechanism that arises from the finely dispersed impurities drag effect.     

Structure and mechanical properties of low temperature magnetron sputtered nanocrystalline (nc-)Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings

This paper reports on the structure and mechanical properties of ~ 2 μm thick nanocomposite (nc-) Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings deposited on 100Cr6 steel substrates, using low temperature (~ 200 °C) DC reactive magnetron sputtering. The carbon content was varied with acetylene partial pressure in order to obtain single layer coatings with different a-C:H carbon phase fractions. The nanocrystalline Ti(N,C) phase is approximately stoichiometric for all coatings and the a-C:H phase fraction increases from 31 to 47 at.% as the coatings stoichiometry changed from TiC_1.34 N_0.51 to TiC_2.48 N_0.48, respectively. TiC_1.34 N_0.51 coatings showed the highest nanoindentation hardness (H) of ~ 14 GPa and a modulus (E_r) of ~ 144 GPa; H reduced to < 6 GPa and E_r to < 70 GPa for TiC_2.48 N_0.48 coatings. nc-Ti(N,C)/a-C:H coatings are promising candidates for applications where better matching of the modulus between a relatively low modulus substrate, hard loading support layer and low modulus-high H/E ratio top layer is required.     

Effect of annealing temperature on magnetic property of Si1 − xCrx thin films

Polycrystalline Si_1 − xCr_x thin films have been prepared by magnetron sputtering followed by rapid thermal annealing (RTA) for crystallization. RTA was performed at 800 °C for 5 min, 1200 °C for 30 s and 1200 °C for 2 min, in a N₂ flow. The magnetic hysteresis loops were observed at room temperature in all the samples except for RTA at 800 °C for 5 min, and the annealing caused the decrease of saturation magnetization relative to the as-grown film. X-ray diffraction spectra and Raman spectra showed that the annealing process lead the deposited amorphous film to be crystallized and CrSi₂ phase formed. The magnetism of the films was determined by the competition between crystallinity and precipitation of diamagnetic CrSi₂ phase.     

Structural analysis of chemically deposited nanocrystalline PbS films

Nanocrystalline PbS films are deposited on glass substrates by chemical bath deposition technique at room temperature. The structural parameters of PbS nanoparticles are studied by X-ray line profile analysis using Williamson-Hall and modified Williamson-Hall plot. The values of average crystallite sizes are found to vary from 12 to 18 nm having very high dislocation density of the order of 10¹⁷ m⁻².     

X-ray diffraction analysis of thermally-induced stress relaxation in ZnO films deposited by magnetron sputtering on (100) Si substrates

Residual stresses in sputtered ZnO films on Si are determined and discussed. By means of X-ray diffraction, we show that as-deposited ZnO films are highly compressively stressed. Moreover, a transition of stress is observed as a function of the post-deposition annealing temperature. After an 800 °C annealing, ZnO films are tensily stressed while ZnO films encapsulated by Si₃N₄ are stress-free. With the aid of in-situ X-ray diffraction under ambient and argon atmosphere, we argue that this thermally activated stress relaxation may be attributed to a variation of the stoichiometry of the ZnO films.     

Strain in electroless copper films monitored by X-ray diffraction during and after deposition and its dependence on bath chemistry

X-ray diffraction based strain measurements have been carried out during the deposition and subsequent relaxation of electroless (autocatalytic) polycrystalline copper films. Thin polymer substrates were mounted on the surface of an electrolyte-filled plating cell, and the X-rays traversed the substrate to scatter of the growing Cu layer. The plating cell was rotated back and forth by up to 70° in order to find the strain of Cu crystallites within and perpendicular to the plane of the film (sin²ψ method). Three types of plating solutions were investigated. A Ni-free solution C leads to compressive strain during steady-state film growth, followed by an exponential relaxation of the film to a residual tensile strain. Electrolytes A and B contain Ni ions, and the resulting Cu(Ni) films have nearly constant strain with small counteracting strain variations during and after film growth. Cyanide-stabilized solution A yields films with a slight compressive strain, while solution B, stabilized by an aromatic nitrogen compound, yields films with tensile strain. Different and reproducible evolution patterns observed for these three electrolyte types establishes in situ X-ray diffraction strain monitoring as a method to evaluate chemical formulations for electroless deposition.     

Effect of substrate temperature and bias voltage on the crystallite orientation in RF magnetron sputtered AlN thin films

The crystal orientation and residual stress of AlN thin films were investigated using X-ray diffraction and substrate curvature method. The AlN films were deposited on Si(100) by RF magnetron sputtering in a mixed plasma of argon and nitrogen under various substrate negative bias V_s (up to − 100 V) and deposition temperature T_s up to 800 °C. The results show that lower temperature and moderate bias favor the formation of (002) plane parallel to the substrate surface. On the contrary, strong biasing beyond − 75 V and deposition temperature higher than 400 °C lead to the growth of (100) plane. At the same time nanoindentation hardness and compressive stress measured by substrate curvature method showed significant enhancement with substrate bias and temperature. The biased samples develop compressive stress while unbiased samples exhibit tensile or compressive stress depending on plasma power and temperature. The relationships between deposition conditions and crystallographic orientation of the films are discussed in terms of surface energy minimization and ion bombardment effects.     

Structural evolution of magnetron sputtered shape memory alloy Ni-Ti films

Near equiatomic and Ti-rich Ni-Ti polycrystalline films have been deposited by magnetron co-sputtering using a chamber installed at a synchrotron radiation beamline. The in situ X-ray diffraction studies enabled the identification of different steps of the structural evolution during film processing.The depositions on a 140 nm amorphous SiO₂ buffer layer heated at 520 °C (without applying bias voltage, V_b, to the substrate) led to a preferential growth of <100> oriented grains of the Ni-Ti B2 phase from the beginning of film growth until the end of the deposition. Films exhibiting a preferential growth of <110> oriented grains of the Ni-Ti B2 phase from the beginning of the deposition were obtained (without and with a V_b of −45 V) by using a TiN coating with a topmost layer formed by <111> oriented grains. Those trends have been observed for the growth of near equiatomic (≈50.0 at.% Ti-Ni) and Ti-rich (≈50.8 at.% Ti-Ni) Ni-Ti films.Additionally, an ion gun had been commissioned, which allows ion bombardment during sputter deposition or post-deposition ion irradiation. In this first series of experiments, a Ni-Ti film was irradiated with He ions after deposition (without exposing the film to the atmosphere, i.e., avoiding surface oxide formation), thus modifying deliberately the microstructure of the film locally.