Reactive Planar Magnetron Sputtering Research Articles

The effect of temperature on the structure of tantalum nitride (TaN) thin films deposited by DC plasma

In this work, we report the effect of growth temperature (room temperature, 150, 200 and 250°C) during the deposition of tantalum nitride thin films by a reactive planar DC magnetron sputtering system on the steel substrates, in a constant nitrogen partial pressure of 15% has been studied. The X-ray spectrum of deposited tantalum nitride films indicated an increasing in intensity of sharp peak of hexagonal TaN and was evidence of grain growth at higher temperatures. By increasing temperature the streaks’ directions, observed from AFM micrographs, were varied.

The influence of the target age on laterally resolved ion distributions in reactive planar magnetron sputtering

Ion energy spectra of negative oxygen ions in a reactive d.c. magnetron sputtering process were investigated with an energy-dispersive mass spectrometer facing zinc targets. The radial distribution of their flux parallel to the target normal was obtained by shifting the magnetron relative to the mass-spectrometer. A plane and an eroded target were studied in comparison. Both targets exhibit a significant radial inhomogeneity of the ion flux peaking opposite the race-track. The inhomogeneity is particularly pronounced for high-energetic ions but still observed at low energy and is much higher for the plane target. Together with a generally decreased ion flux for the eroded target it is concluded that the distribution of energetic bombardment of the substrate changes distinctly with the erosion of planar magnetron targets. The energy distribution of the low-energetic ions further suggests that they are formed in the pre-sheath of the target.

The Effect of Substrate Temperature on the Structure and Morphology of Titanium Nitride Compounds Grown by DC Magnetron Sputtering

The TiN thin films were deposited on p-type silicon (100) substrates using reactive planar DC magnetron sputtering system. The target was 99.99% pure Ti. The reactive sputter gas was a mixture of Ar (99.999%) and N2 (99.999%) with the ratio Ar (97%) and N2 (3%) by volume. Structural characterization of the coating was done using X-ray diffraction (XRD). The surface roughness of the coating was determined using an Atomic Force Microscope (AFM). The reflectivity of thin films was investigated by a spectrophotometer system. The X-ray diffraction measurements showed that by increasing the substrate temperature during the growth, change in crystalline structure will occur. The crystallite size of the films determined by Scherrer’s equation, and the crystallite size measured by AFM also increased by increasing the substrate growth temperature. The surface reflectivity measurements indicate that by increasing the substrate growth temperature, the optical properties of the films changes. The change in optical properties and crystalline structure of the films indicate that substrate growth temperature plays an important role in structure and morphology of the grown layers.

Effects of N 2 content and thickness on CrN x coatings on Mg alloy by the planar DC reactive magnetron sputtering

The CrN x (0 < x = N/Cr < 1) coatings on Mg alloy were prepared by DC reactive planar magnetron sputtering at a mixed atmosphere containing Ar and N 2. The effects of N 2 content and thickness on the CrN x coatings were characterized by the X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The experimental results show that the N atomic concentration increases exponentially and N1s spectrum shifts downward with the increase in N 2 content ( φ(N 2)), and the deposition rate decreases exponentially. The morphologies evolution of CrN x coatings shows that the growth structure changes from fibre growth to columnar growth with the increase in φ(N 2). Based on evolution of phase and structure, a SZM model is summarized, indicating that the change of structure and phase is consistent; ZT and sub-ZT correspond to Cr 2N + Cr and CrN + Cr 2N, respectively. The in-plane mean grain size linearly increases and the Root Mean Square roughness W RMS increases exponentially with coating thickening, and grain size obeys Gaussian distribution.

Electrical and optical properties of indium tin oxide thin films deposited on unheated substrates by d.c. reactive sputtering

Transparent conducting thin films of indium tin oxide (ITO) have been deposited by d.c. reactive planar magnetron sputtering by using metal InSn alloy target in an ArO 2 gas mixture. The study demonstrates that the deposition on unheated substrates achieved sheet resistance of as low as about 50–60 Ω/□ (or a resistivity of abouts 7 × 10 −4 Ω cm), and visible transmission of about 90% for a wavelength of 420 nm. The effects of heat treatment at 450 °C in air depends on the deposition conditions of the as-deposited ITO films. Although annealing improves the properties of as-deposited ITO films which were deposited with non-optimum conditions, the optimized condition for the formation of the film in the as-deposited state is essential to obtain a high quality transparent conducting coating.

Fabrication of NbN/MgO/NbN tunnel junctions

NbN/MgO/NbN superconductor tunnel junction devices of area 5 μmx5 μ and 10 μmx10 μm have been fabricated using a bactch-process self-aligning technique. NbN deposition was performed by a new technique involving control and optimization of the target voltage-nitrogen flow hysteresis curve in reactive planar magnetron sputtering. The choice of NbN deposition conditions reflected a compromise between optimum critical temperature, film smoothness, and intrinsic film stress. After patterning of NbN/MgO/NbN trilayers to define top and bottom NbN electrodes, evaporated SiO was deposited as the passivation layer. A liftoff technique was used to define the vias for NbN interconnects through the SiO. Each quartz substrate contained 65 structures, including single junctions and multiple junctions in series. Characterization of these devices has shown a gap voltage of 4.1 mV, and critical current densities near 1000 A cm -2.

Reactive Planar Magnetron Sputtering System with Obliquely Facing Targets of Zn

Planar magnetron sputtering system with obliquely facing targets was constructed to prepare ZnO films, and the possibility of the application of this sputtering system to the practical preparation of ZnO was studied. The films were prepared by the sputtering of Zn in O2 (100%) and the target-substrate configuration was arranged to avoid film bombardment by energetic oxygen particles. Gas pressure dependence of the c-axis orientation of the film was estimated. The presented sputtering system provided more highly c-axis-oriented polycrystalline films of ZnO than ordinary planar magnetron sputtering.

Properties of reactively sputtered NbN films

The variation of the properties of niobium nitride (NbN) thin films as a function of argon partial pressure and nitrogen flow were studied. The films were deposited by dc reactive planar magnetron sputtering onto unheated substrates. All of the films were superconducting and had the B1, face-centered cubic crystal structure. A number of films deposited at argon partial pressures of 5 and 7 mTorr had superconducting critical temperatures (Tc ) of 15.6 K and grain sizes of 100–120 nm. The film morphology showed a zone 1 to zone T transition as the argon partial pressure was decreased from 12 to 5 mTorr. Films deposited below 5 mTorr exhibited excessive tensile stress (&amp;gt;1.9×109 N/m2) and delaminated from the substrate.

Structure and Properties of C-Axis Oriented AlN Films Reactively Deposited by DC Planar Magnetron Sputtering

AbstractAluminum nitride (AlN) films have been deposited by reactive DC planar magnetron sputtering at a low substrate temperature of 80°C. An Al disk and either N2 or NH3 were used as a target and an ambient gas, respectively. In films deposited in N2, the c-axis of AlN crystallites was perpendicular to the film plane. On the other hand, in NH3, X-ray diffraction peaks from (100), (110) and (200) were observed. The surface and the cross-sectional microstructures of AlN films deposited in N2 were significantly different from that deposited in NH3. The surface of films deposited in NH3 was smoother than that deposited in N2. The transmittivity of films deposited in NH3 was superior to that deposited in N2 in wavelength of 275∼450 nm. Resistivities of films deposited in N2 and in NH3 were 1014sim;1015 Ω · cm. Dielectric constants of films deposited in N2, and of that deposited in NH3, were 9.7, and 9, respectively, in a frequency range of 20 kHz to 20 MHz. The structure and the properties of AlN films deposited by this method depended on kind of ambient gas.

A control process for stable operation of a high rate dc reactive planar magnetron sputtering system: R W Lewin, A G Spencer and R P Howson, Department of Physics, Loughborough University of Technology, Ashby Road, Loughborough, Leicestershire LE11 3TU, UK

A control process for stable operation of a high rate dc reactive planar magnetron sputtering system: R W Lewin, A G Spencer and R P Howson, Department of Physics, Loughborough University of Technology, Ashby Road, Loughborough, Leicestershire LE11 3TU, UK

NbN film deposition using optical emission spectroscopy

NbN films were deposited on unheated Si substrates by dc and rf reactive planar magnetron sputtering of Nb in an Ar and N 2 gas mixture. The optical emission spectrum of the plasma was recorded for different sputtering conditions and the target sputtering rate was found to be proportional to the intensity of any Nb emission line. A model for the reactive sputtering mechanism was developed and the optimum sputtering parameters were selected by observing the change in the Nb emission line intensity as a function of the partial pressure of nitrogen. The critical temperatures of the films were in the 13 to 15.8 K range.

Synthesis and properties of superconducting lanthanum sulfide films

We report the structural and transport properties of La-S films prepared by reactive planar magnetron sputtering. The La-S (Th 3P 4 cubic structure) can be prepared over a range of compositions with the electronic properties varying from a low electron density superconductor ( T c ≈ 7 K) to a semiconductor which shows thermally activated transport at low temperature. This method of deposition produces small grained (≈ 200 Å) polycrystalline films whose composition can be varied continuously by tuning the deposition parameters. We discuss the TEM and X-ray data as well as the resistivity, Hall effect and superconducting properties of these films. We find that the superconducting transition temperature of the films is the same as that of bulk single crystals; however the mobility is a factor of 2 to 300 lower than that found in bulk specimens.

Optical properties of tungsten oxide films as a function of their stoichiometry as determined by LIMA and XPS

Tungsten oxide can be produced as a thin film with a variety of compositions and doping to give coloured films which can be electrochromic. Electrochromic films are of interest in large areas as solar control devices and as alternatives to liquid crystal display panels. The preparation of such films by reactive planar magnetron sputtering is described. The compositions of the deposited films were obtained by laser induced mass analysis (LIMA) and X-ray photoelectron spectroscopy (XPS). The stoichiometry was then related to both the film properties and to the deposition conditions. The use of these two analytical techniques also allowed the influence of doping by hydrogen to be assessed. This information was used to create a system which would coat tungsten oxide films, with controlled stoichiometry, on to long polyester sheets which had previously been coated with a transparent electrically conducting coating. This coated polyester was then suitable for use as part of an electrochromic device.

Optical coatings for large area interference filters

The appearance of optical filters on large scale as heat reflecting coatings on domestic windows, heralds the advent of techniques and materials for a range of applications which are far removed from the ultra-high performance, and cost, of multilayer filters used hitherto. These new coatings use interference anti-reflection layers on either side of a thin metal layer. They are prepared by high rate reactive planar magnetron sputtering onto a large area of glass or plastic substrate. This technique is critically assessed and materials considered which will allow more complex filters to be made. In particular the preparation of a high index dielectric film of SnO 2 and a low index film of aluminium oxyflouride is described. Illustrations of some applications of these are given.

Optimized transparent and heat reflecting oxide and nitride films

Films of indium oxide and indium oxide doped with tin have been produced by reactive planar magnetron sputtering of the pure metal and the alloy and from two metal sources simultaneously. In each case the oxygen partial pressure was controlled to give the higher sheet resistance in the oxide film which was deposited onto a plastic sheet transferred over a drum at ambient temperature. Films prepared under these conditions with the best properties for heat reflecting and visible transparent filters were found to be the oxide of the pure metal. A radio frequency discharge used in conjunction with the magnetron allowed the operating pressure to be considerably reduced, which allowed the preparation of titanium nitride films from a titanium metal target and the construction of simple metal and dielectric-metal-dielectric filters, which match theoretical predictions. A sandwich filter could be made from one titanium target by varying the active gas between oxygen and nitrogen to give a structure of: TiO 2TiNTiO 2.

Reactive ion plating of TiO 2

TiO 2 films have been produced from a variety of sources utilising various ion assisted techniques to provide surface energy. It was found that reactive rf bias ion plating using electron beam evaporated titanium metal could give films of refractive index of close to 2.5 and equivalent to those made by conventional reactive evaporation onto substrates at elevated temperatures. Neutralised ion beam and oxygen plasma guns were not so successful, as was the use of sources of TiO 2 and TiO. Reactive planar magnetron sputtering of titanium metal could be equally successful if the source was operated in the metal sputtering mode, this could be achieved with sufficient stability with the use of a pulsed flow of the oxy gen supply.

Transparent conducting zinc oxide and indium–tin oxide films prepared by modified reactive planar magnetron sputtering

Transparent conducting layers for liquid crystal displays and plastic substrates must be deposited without significant heating. A planar magnetron sputtering process which provides a suitable combination of resistivity and transparency on unheated substrates has been developed. Transparent conducting films of ZnO and indium tin oxide (ITO) have been deposited by sputtering Zn and In0.9Sn0.1 targets in a planar magnetron system modified to introduce oxygen near the substrate and to reduce the conductance for oxygen to the target. As the oxygen flow rate f2 increased, the dc voltage Va, required to maintain constant sputtering current, first increased and then decreased rapidly as the critical flow rate f2c, at which the target oxidizes, is approached. In the ZnO case, Va had a maximum value of 525 V and was 355 V after the target oxidized; transparent conducting films were obtained at 435 V but the best films were obtained by activating an rf discharge close to the substrate to increase the oxidation rate. These polycrystalline films had a transmittance of 80% and a resistivity of 0.03 Ω cm but their chemical stability was too poor for useful application. In the ITO case, the rf discharge was necessary to obtain transparent conducting films. Even at f2/f2c=0.94, films were opaque in the absence of this extra oxidation mechanism. Films with a transmittance of 79% and a resistivity of 1×10−4 Ω cm were obtained by coupling an rf power of 105 W to the substrate holder, with a substrate self-bias voltage less than 5 V, at f2/f2c=0.77. These films are amorphous and chemically stable. This sputtering process provides a maximum deposition rate of 48 nm/min on unheated substrates and is suitable for fabricating MIM-addressed liquid crystal displays.

High rate planar magnetron deposition of transparent, conducting, and heat reflecting films on glass and plastic

Films of indium tin oxide (ITO) and ZnO have been deposited by dc reactive planar magnetron sputtering of metal targets in an Ar/O2 atmosphere. Control of film stoichiometry was achieved through an applied rf bias to the substrate, a reactive gas baffle surrounding the target, and computer control of all parameters in the sputtering process, such as cathode voltage, gas flow, and substrate bias. Films were deposited on cold glass substrates as well as on rolls of polyester sheet. Both the ITO and ZnO films were highly conducting, visually transparent, and infrared reflecting. The success of this deposition technique applied to ZnO films identifies ZnO as a new candidate for transparent, heat reflecting coatings.

High rate deposition of transparent conducting films by modified reactive planar magnetron sputtering of Cd 2Sn alloy : S Maniv et al, J Vac Sci Technol, 18 (2), 1981, 195–198

High rate deposition of transparent conducting films by modified reactive planar magnetron sputtering of Cd 2Sn alloy : S Maniv et al, J Vac Sci Technol, 18 (2), 1981, 195–198

Voltage controlled, reactive planar magnetron sputtering of AlN thin films

Three operating modes for planar magnetron sputtering are investigated for the purpose of controlling the stoichiometry of AlNx (0?x?1) films: (1) controlled gas flow rates at constant power, (2) controlled power at constant flow rates, and (3) controlled cathode voltage at constant flow rates. Whereas modes (1) and (2) are found to exhibit runaway transitions associated with target coverage, mode (3) is shown to provide a means for stable operation for any degree of target coverage (0?x?1).