Characterization of zirconium oxynitride films obtained by radio frequency magnetron reactive sputtering

Thin ZrN_xO_y films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon-oxygen-nitrogen mixture. The Φ_N2/Φ_{(Ar + N2 + O2)} ratio was varied in the range 2.5%-100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO₂, ZrN, ZrON and N-rich zirconium nitride which is correlated with the Φ_N2/Φ_{(Ar + N2 + O2)} values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution.     

Raman spectra and structural analysis in ZrOxNy thin films

Raman spectroscopy has been used as a local probe to characterize the structural evolution of magnetron-sputtered decorative zirconium oxynitride ZrO_xN_y films which result from an increase of reactive gas flow in the deposition. The lines shapes, the frequency position and widths of the Raman bands show a systematic change as a function of the reactive gas flow (a mixture of both oxygen and nitrogen). The as-deposited zirconium nitride film presents a Raman spectrum with the typical broadened bands, due to the disorder induced by N vacancies. The recorded Raman spectrum of the zirconium oxide film is typical of the monoclinic phase of ZrO₂, which is revealed also by X-ray diffraction. Raman spectra of zirconium oxynitride thin films present changes, which are found to be closely related with the oxygen content in films and the subsequent structural changes.     

Sputtering deposition and characterization of zirconium nitride and oxynitride films

The interest about zirconium oxynitrides is growing with the attention for zirconium nitrides phase at high zirconium content. In recent years a great progress has been made to realize both the higher nitride phase (Zr₃N₄) and the higher oxynitride phase (Zr₂ON₂) in more ordered crystal structures. In this work the abovementioned two phases are realized by RF magnetron sputtering technique. The characterization results, illustrated in the present paper, push towards the evidence of an evolution from zirconium N-rich nitride to the oxynitride films by introducing a very small percentage (0.5%) of water vapor in a sputtering atmosphere made only of nitrogen gas. In particular, structural analysis identified zirconium N-rich nitride as c-Zr₃N₄ and zirconium oxynitride as c-Zr₂ON₂. The formation of zirconium oxynitride is due to oxygen presence, coming from the water dissociation in the plasma. Both phases request an additional energy supplied by substrate bias assistance for c-Zr₃N₄ and by more energetic particles reflected by the Zr target for c-Zr₂ON₂.     

Stable deposition of silicon oxynitride thin films with intermediate refractive indices by reactive sputtering

The deposition stability of silicon oxynitride thin films with intermediate refractive indices was investigated as a function of argon concentration in the process gas mixture. The silicon oxynitride thin films were deposited by pulsed dc reactive magnetron sputtering in a mixture of argon, nitrogen and oxygen. The refractive indices of the silicon oxynitride thin films gradually decreased with oxygen percentage in the reactive gas mixture when high argon concentrations were used. It is proposed that many silicon atoms were sputtered from the target and reached the substrates in high argon concentrations; consequently, drastic oxidation of the thin films did not occur.     

Characterization of bi-phased Zr2ON2–ZrO2 coatings deposited by RF magnetron sputtering

The aim of this work is to develop zirconium oxynitride coatings by RF magnetron sputtering on silicon substrates. The film properties were analyzed as a function of oxygen flux percentage in two different inert gas atmospheres namely argon and helium. At low oxygen flux percentage, Zr₂ON₂ and ZrO₂ phases are observed from the structural characterization by X-ray diffraction. The atomic ratio of nonmetallic to metallic atoms (N + O)/Zr content varies from 1.22 to 2.03 for zirconium oxynitride films deposited in argon atmosphere and from 1.43 to 2.33 for films deposited in helium atmosphere. The thickness of the film was measured by surface profiler and the growth rate decreases from 11.33 to 5.1 nm/min for films deposited in argon atmosphere and from 7.01 to 3.75 nm/min for films deposited in helium atmosphere with increase in oxygen flux percentage. The films deposited are hydrophobic and the contact angle was measured by contact angle measuring system. Higher surface roughness and maximum contact angle values of 100° and 103° are observed for films deposited in argon and helium atmosphere respectively at low oxygen flux percentage (2.5%). The surface energy of films was calculated by two methods: Owens-Wendt's geometric mean and Wu's harmonic mean approach. The elevated surface energy values were observed with increase in oxygen flux percentage. The stress measurements of the deposited films were done by sin²ψ X-ray diffraction method which depends on the variation of Zr₂ON₂ and m-ZrO₂ phases.     

Electrical properties of AlNxOy thin films prepared by reactive magnetron sputtering

Direct current magnetron sputtering was used to produce AlN_xO_y thin films, using an aluminum target, argon and a mixture of N₂ + O₂ (17:3) as reactive gases. The partial pressure of the reactive gas mixture was increased, maintaining the discharge current constant. Within the two identified regimes of the target (metallic and compound), four different tendencies for the deposition rate were found and a morphological evolution from columnar towards cauliflower-type, ending up as dense and featureless-type films. The structure was found to be Al-type (face centered cubic) and the structural characterization carried out by X-ray diffraction and transmission electron microscopy suggested the formation of an aluminum-based polycrystalline phase dispersed in an amorphous aluminum oxide/nitride (or oxynitride) matrix. This type of structure, composition, morphology and grain size, were found to be strongly correlated with the electrical response of the films, which showed a gradual transition between metallic-like responses towards semiconducting and even insulating-type behaviors. A group of films with high aluminum content revealed a sharp decrease of the temperature coefficient of resistance (TCR) as the concentration ratio of non-metallic/aluminum atomic ratio increased. Another group of samples, where the non-metallic content became more important, revealed a smooth transition between positive and negative values of TCR. In order to test whether the oxynitride films have a unique behavior or simply a transition between the typical responses of aluminum and of those of the correspondent nitride and oxide, the electrical properties of the ternary oxynitride system were compared with AlN_x and AlO_y systems, prepared in similar conditions.     

Structural,Wettability and Optical Investigation of Titanium Oxynitride Coatings:Effect of Various Sputtering Parameters

The objective of the present work is to investigate the effect of various sputtering parameters such as nitrogen flow rate,deposition time and sputtering pressure on structural,wettability and optical properties of titanium oxynitride films deposited on glass substrate by reactive magnetron sputtering.The X-ray diffraction graphs of titanium oxynitride films show evolution of various textures of TiO_xN_y and TiN phases with increasing nitrogen flow rate and deposition time,but an increase in sputtering pressure from 4.0 to 8.0 Pa results in decline of various textures observed for TiO_xN_y and TiN phases.The stress and strain calculated by sin~2Ψ method are compressive,which decrease with increasing nitrogen flow rate from 55 to 100 sccm(standard cubic centimeter per minute) and increase with increasing deposition time from 80 to 140 min due to atomic penning effect and increasing thickness of the deposited films.The titanium oxynitride films have contact angle values above 90 deg.,indicating that films are hydrophobic.The maximum contact angle of 109.1 deg.is observed at deposition time of 140 min.This water repellent property can add value to potential protective,wear and corrosion resistant application of titanium oxynitride films.The band gap decreases from 1.98 to 1.83 eV as nitrogen flow rate is increased from 55 to 100 sccm;it decreases from 1.93 to 1.79 eV as deposition time is increased from 80 to 140 min as more nitrogen incorporation results in higher negative potential of valence band N2p orbital.But it increases from 2.26 to 2.34 eV for titanium oxynitride films as sputtering pressure increases from 4.0 to 8.0 Pa.     

One-step growth of HfSiON films

Hafnium silicate (HfSiO) has been identified as a promising candidate to replace silicon oxide/oxynitride as a high-κ material for gate dielectric applications. Nitrided hafnium silicate has been found to have a number of advantages in film performance. However, two-step processes have been commonly used, i.e. the first step is the deposition of HfSiO film by CVD, ALD or other techniques, and the second step is film nitridation. In this research, HfSiON films (Hafnium silicon oxynitride, or nitrided HfSiO) were directly deposited on Si substrate by Chem. Vap. Depos. using trisilylamine (TSA) and tetrakis(diethylamido)hafnium(IV) (TDEAH) precursors. TSA, a highly volatile and carbon-free precursor, was used as the Si source and was delivered in pure vapor phase without heating. TDEAH was used as the Hf source and delivered by direct liquid injection (vaporizer). HfSiON films were deposited in a single step with no need of a post treatment process for nitrogen incorporation. The HfSiON films can be tuned in wide compositional (Hf, Si, O, N) ranges and high growth rates were achieved. The addition of NH₃ to the reactant gas stream was found to be able to deposit films with high and controllable N content. It was also found that NH₃ had significant impact on film growth rate and composition.     

Protection of organic light-emitting diodes over 50 000 hours by Cat-CVD SiNx/SiOxNy stacked thin films

Silicon oxynitride (SiO_xN_y) films have been formed by adding proper amount of oxygen gas to usual forming condition of silicon nitride (SiN_x) films in catalytic chemical vapor deposition (Cat-CVD) method. The composition and refractive index of the film can be systematically controlled by changing oxygen flow rate. Organic light-emitting diodes (OLEDs) covered with SiN_x/SiO_xN_y stacked films have been completely protected from damage due to oxygen and moisture and their initial emission intensity is maintained over 1000 hours under 60 °C and 90% RH, which is equivalent to 50 000 hours in normal temperature and humidity conditions.     

Structures and photocatalytic behavior of tantalum-oxynitride thin films

Tantalum oxynitride films were created by direct nitridation/oxidation during rapid thermal annealing at temperatures 450-700 °C. Instead of during deposition, this post process may be proved to be an alternative way to make transition metallic oxynitride films. With sufficient supply of oxygen flow (≥ 30 sccm), TaO_xN_y was formed as examined from X-ray diffraction (XRD) analysis. This oxynitride film has a broad optical absorption over the range of visible light and sufficient photocatalytic function. For optical absorption, the films' transmittance and reflectance were measured by a UV-VIS-NIR spectrophotometer with wavelengths ranging from 300 to 900 nm. The broad visible light absorption is associated with the formation of band gap in TaO_xN_y film, which was examined by the theoretical calculations combining the Beer-Lambert law and Tauc formula. Lastly, the photocatalysis of TaO_xN_y was gauged by the photodegradation test which measured the reduction of light absorbance affected by the decomposition of methylene blue (C₁₆H₁₈N₃SCl.3H₂O) on TaO_xN_y under visible light irradiation.     

X-ray photoelectron spectroscopy analyses of titanium oxynitride films prepared by magnetron sputtering using air/Ar mixtures

X-ray photoelectron spectroscopy (XPS) has been employed to investigate titanium oxynitride (TiN_xO_y) films prepared by d.c. magnetron sputtering using air/Ar mixtures, which allows one to perform the deposition at a high base pressure (1.3 × 10^− 2 Pa) and can reduce substantially the processing time. XPS analyses revealed that all the prepared TiN_xO_y films comprised Ti-N, Ti-N-O, and Ti-O chemical states. When the air/Ar ratio was below 0.3, nitrogen-rich TiN_xO_y films were obtained. As the air/Ar ratio was above 0.4, oxygen-rich TiN_xO_y films were formed. XPS depth profile analyses were also performed in selected specimens. It has been found that at relatively low air/Ar ratios, such as 0.5, the oxygen content of the films increased toward the film/substrate interface and when the air/Ar ratio was higher, TiN_xO_y films with large oxygen content with uniform concentrations were then formed.     

Structural and optical investigation of sputter deposited hydrophobic chromium oxynitride films

Nanocrystalline chromium oxynitride films were deposited by reactive RF magnetron sputtering of metallic chromium target in argon and helium atmospheres. The paper deals with consequence of increase in oxygen partial pressure on structural, hydrophobic and optical properties of chromium oxynitride films. The film stoichiometry changes from CrN and Cr₂O₃ to only Cr₂O₃ with increase in oxygen partial pressure as evident from X-Ray Diffraction analysis in both cases. The average crystallite size decreases with increase in oxygen partial pressure for both gas atmospheres. The thickness calculated from transmission data and surface profilometer are in good harmony with each other. The deposited films are hydrophobic by nature and the contact angle of the films varies as a function of surface roughness. Surface energy of the films is inversely proportional to the observed contact angle values. As oxygen partial pressure increases, the optical properties: transmission and band gap values increases as determined by Ultraviolet-visible-Near Infrared spectrophotometer in both cases. This film can have potential applications as insulating, hydrophobic and corrosion resistant protective coatings.     

Preparation of ZrNxOy films by magnetron sputtering using air as a reactive gas

Zirconium oxynitride (ZrN_xO_y) thin films were prepared by d.c. magnetron sputtering using air as a reactive gas. Replacing conventionally used N₂/O₂ with air as a reactive gas allows the process to perform at high base pressures (low vacuum), which could drastically reduce the processing time. The color of the obtained films changed from light golden and dark golden for low air/Ar flow ratios, to dark violet and bright cyan for high air/Ar ratios. X-ray diffraction patterns show that the films transformed from ZrN and Zr₂ON₂ mixed phases to a Zr₂ON₂ phase, and then an m-ZrO₂ phase. The thickness of the films decreased slightly with increasing the air/Ar flow ratio. ZrN_xO_y films possessed a mixture of Zr-N-O, Zr-N and Zr-O chemical binding states determined from X-ray photoelectron spectroscopy. ZrN_xO_y films with mainly a Zr₂ON₂ phase exhibited the band gap of 1.96-2.26 eV, while the m-ZrO₂ films with slight nitrogen incorporation had a band gap of 2.32 eV, evaluated from transmittance spectra. By varying the air/Ar ratio during deposition, the nitrogen/oxygen content of the films could be controlled and hence, the color, crystal structure, atomic composition, and band gap of the films could be tailored.     

Reactive DC magnetron sputter deposited Ti-Cu-N nano-composite thin films at nitrogen ambient

Ti-Cu-N thin films have been grown on Si(111), KBr (potassium bromide), quartz and glass slide substrates using a TiCu (13:87 at. %) single multi-component target by reactive DC magnetron sputtering at nitrogen ambient. This study provides insight into the importance of nitrogen pressure on the characteristic of Ti-Cu-N thin films. Crystalline phases of these films are identified by X-ray diffraction (XRD) technique. The titanium atoms were inserted into the Cu₃N unit cell. The results from XRD show that the observed phases are nano-crystallite cubic anti-Rhenium oxide (anti-ReO₃) structure of Ti doped Cu₃N (Ti:Cu₃N) and nano-crystallite face centre cubic (fcc) structure of Cu. Formation of copper vacancies in Cu₃N cell substituted by titanium atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion and optical energy gap widening. Surface morphology of the films studied by scanning electron microscope (SEM) indicates agglomeration of grains. Ti:Cu atomic ratio of Ti-Cu-N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of the original TiCu single multi-component target and nearly independent of nitrogen pressure. Optical study is performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance using a reverse engineering method. Absorption coefficient indicates that the nitrided films are direct semiconductor. The films electrically show quasi-metallic behavior. The effect of sputtering pressure on deposition rate is investigated. Compared with the Ti free Cu₃N film, the Ti:Cu₃N films possesses fine thermal stability in vacuum.     

Study of the effect of plasma current density on the formation of titanium nitride and titanium oxynitride thin films prepared by reactive DC magnetron sputtering

Titanium nitride and titanium oxynitride films were deposited by varying the plasma current density from 10 mA/cm² to 40 mA/cm² using DC magnetron sputtering at constant gas flow rate and deposition time. Samples were characterized by Grazing Incidence X-Ray Diffraction, XPS, Nanoindentation and colorimetric analysis. Different coloured films like golden, blue, pink and green were obtained at different current densities. At lower current density (10 mA/cm²), golden coloured stoichiometric titanium nitride film was formed. At higher current densities (20, 30 and 40 mA/cm²), non stoichiometric Titanium oxynitride films of colour blue, pink and green were formed respectively. The thickness of the films increased with plasma current density from 43 nm to 117 nm. It was found that the colour variation was not only due to thickness of the film but also due to oxygen atoms replacing the nitrogen positions in TiN lattice. Hardness and Young Modulus of the films were found to decrease from 17.49 GPa to 7.05 GPa and 319.58 GPa-246.77 GPa respectively with increasing plasma current density. This variation of hardness and Young Modulus of the films can be speculated due to change in crystal orientation caused by oxygen incorporation in the films. The film resistivity increased from 16.46 × 10⁻⁴ to 3.28 × 10⁻¹ Ω cm for increasing plasma current density caused due to oxygen incorporation in the crystal lattice.     

Optical, electrical and mechanical properties of the tantalum oxynitride thin films deposited by pulsing reactive gas sputtering

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a Ta target and N₂ and O₂ as reactive gases. The nitrogen flow was kept constant while the oxygen flow was pulsed periodically. The film composition evolves progressively from TaO_0.25N_1.51 to TaO_2.42N_0.25 while increasing the oxygen pulse duty cycle without any abrupt change in the elemental content. The optical transmission spectra of the films deposited on glass show a “blue shift” of the absorption edge with increasing oxygen content. X-ray diffraction (XRD) patterns of all films exhibit broad peaks typical for nanocrystalline materials. Cross-section film morphology is rather featureless and surface topography is smooth exhibiting very small grains, in agreement with the results obtained by XRD. The optical properties of the films are very sensitive to their chemical composition. All films exhibit semiconducting behaviour with an optical band gap changing from 1.85 to 4.0 eV with increasing oxygen content. In order to evaluate the potential of the tantalum oxynitride films for microelectronic applications some Ta-O-N films were integrated in a MOS structure. The results of the capacitance-voltage measurements of the system Al//Ta-O-N//p-Si are discussed with respect to the chemical composition of the Ta-O-N films.     

Structure and chemical bonds in reactively sputtered black Ti-C-N-O thin films

The evolution of the nanoscale structure and the chemical bonds formed in Ti-C-N-O films grown by reactive sputtering were studied as a function of the composition of the reactive atmosphere by increasing the partial pressure of an O₂ + N₂ gas mixture from 0 up to 0.4 Pa, while that of acetylene (carbon source) was constant. The amorphisation of the films observed by transmission electron microscopy was confirmed by micro-Raman spectroscopy, but it was not the only effect associated to the increase of the O₂ + N₂ partial pressure. The chemical environment of titanium and carbon, analysed by X-ray photoemission spectroscopy, also changes due to the higher affinity of Ti towards oxygen and nitrogen than to carbon. This gives rise to the appearance of amorphous carbon coexisting with poorly crystallized titanium oxynitride. The evolution of the films colour is explained on the basis of these structural changes.     

Electronic structure and optical properties of zirconia

The effects of substitutional impurities and oxygen vacancies on the electronic structure and optical properties of cubic zirconia were studied using band-structure calculations. It is shown that oxygen vacancies produce additional states near the Fermi level, whereas impurity atoms make an insignificant contribution to the states in the valence band and at the bottom of the conduction band, and their effect has a predominantly electrostatic character. The mechanisms of the stabilization of the high-temperature ZrO₂ polymorphs are elucidated. The calculation results agree well with x-ray photoelectron spectroscopy and optical data     

Properties of ZrNx films with x > 1 deposited by reactive radiofrequency magnetron sputtering

Thin ZrN_x films have been prepared by reactive radiofrequency magnetron sputtering varying the nitrogen partial pressure in the range 0-3.26 Pa. The films have been analyzed by X-ray photoelectron spectroscopy (XPS) and by optical characterization in the UV-Vis-IR range. The cross-section and surface morphology of the samples were examined by means of field emission gun-scanning electron microscopy. The effects of the nitrogen partial pressure on the ZrN_x films stoichiometry have been studied correlating the N 1s photoelectron peaks with different bounding states for the zirconium nitride. The XPS depth profile analysis has revealed the presence of metastable phases (ZrN₂, Zr₃N₄) that vanishes when lowering the nitrogen partial pressure. The optical analysis has permitted to distinguish two different behaviours of the deposited samples in the visible range: semi-transparent and absorbent. Drude-Lorentz model fitted the behaviour of absorbent films, while the O'Leary model was applied to the semi-transparent ones. The semi-transparent films had a band gap varying between 2.36 and 2.42 eV, typical values of N-rich zirconium nitride films. Morphological analysis showed a compact and dense columnar structure for all the samples. A simple growth model explains the presence of the different nitride phases considering implantation and re-sputtering effects.     

Properties of MoNxOy thin films as a function of the N/O ratio

The main purpose of this work is the preparation of single layer films of molybdenum oxynitride, MoN_xO_y. The films were deposited on steel substrates by dc reactive magnetron sputtering. The depositions were carried out from a pure Mo target and varying the flow rate of reactive gases. This allowed tuning of the crystallographic structure between insulating oxides and metallic nitrides and consequently changes in the electronic, mechanical and optical properties of the material. X-ray diffraction (XRD) results revealed the presence of molybdenum nitride for the films with low oxygen fraction: face-centered cubic phases (γ-Mo₂N) for low nitrogen flow rate or cubic MoN_x and hexagonal phase (δ-MoN) for high nitrogen flow rate. The increase of oxygen content induces an amorphization of the nitride phases and the appearance of MoO₃ phases. The increase of the oxygen fraction in the films induces also a high decrease in the film's hardness. Residual stresses were compressive, in the range of very few tenths of GPa to − 2 GPa. These results will be presented as a function of the deposition parameters, the chemical composition and the structure of the films.