Conventional Reactive Magnetron Sputtering Research Articles

Correlation between plasma parameters and structure of thin TiO2 films deposited by conventional and pulsed magnetron sputtering methods

The aim of the work was to diagnose plasmas excited by two magnetron sputtering techniques: conventional reactive magnetron sputtering (RMS) and magnetron sputtering realized under gas impulse conditions (GIMS) with use of light emission spectroscopy and Langmuir probing. The plasmas were studied during deposition of TiO2 coatings by magnetron sputtering of Ti target in O2 atmosphere. The obtained deposits were investigated with use of infrared spectroscopy (FTIR) and X-ray diffraction (GIXRD).Two major conclusions were drawn from the investigations. One concerned the mechanism of TiO2 formation during reactive sputtering. An absence of emission lines corresponding to plain Ti atoms proves that their oxidation takes place at the surface of the Ti target without any gas phase reactions. The second conclusion concerned deposition thermodynamics. Although the diagnostics of the GIMS plasma revealed a greater plasma density and electron temperature than in the RMS one, it was the latter technique that produced more high temperature polymorph of TiO2. It appears that the pulse technique offers a way to control thermodynamic conditions of deposition in a broad range up to a conversion to the RMS mode of deposition.

Rational Design of Oxygen Deficiency-Controlled Tungsten Oxide Electrochromic Films with an Exceptional Memory Effect.

Owing to their nonemissive characteristics, electrochromic materials promise distinct advantages in developing next-generation eye-friendly information displays. Yet, it remains a challenge to manipulate the structure of the materials to achieve a strong memory effect with high optical contrast, which is of importance for displaying images with essentially zero energy consumption. Here, we design a mixed crystalline WOx thin film implanted with massive oxygen deficiencies based on a conventional reactive magnetron sputtering process. The obtained WOx film exhibits high dual-band optical modulation in both visible (VIS, 99.0% in 633 nm) and near-infrared (NIR, 94.2% in 1300 nm) regions as well as an exceptional memory effect (the colored transmittance increases only by 0.04% at 633 nm after 50 days). The enhanced electrochromic performance can be attributed to dense Li+-ion binding sites as well as the trapping effect provided by the massive internal oxygen deficiencies. The strategy in this work bestows the WOx thin film a promising candidate for developing electrochromic information displays and other energy-efficient devices as well.

Reactive plasma deposition of high quality single phase CuO thin films suitable for metal oxide solar cells

Copper oxides are of great potential as active optical absorbing materials for low-cost solar cells based on sustainable and green materials resources. In this work, CuO thin films are deposited at room temperature by reactive sputtering deposition using a novel high target utilization system (HiTUS). The films were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy, atomic force microscopy, UV–vis-near infrared absorption spectroscopy, and Hall measurement. The results showed that the deposition rate, phase structures, optical, and electrical properties of copper oxide films were strongly dependent on the sputtering power and the oxygen flow rate. The as-deposited films were characteristically polycrystalline, without evident preference in crystal orientations. This led to highly compact films without the formation of through-thickness columnar grain boundaries typical to conventional reactive magnetron sputtering deposited films. Optical absorption spectroscopy showed that all the CuO films from this work exhibited an indirect optical bandgap about 1.5 eV, without evident effect from the oxygen flow rates. Hall measurement revealed that the CuO films were of p type conductivity, with their hole concentration being readily tunable in a wide range of 1017–1022 cm−3. The ability for refined tuning of the concentration of charged carriers (holes) is critical in realizing the great potential in engineering delivery of CuO photovoltaic (PV) cells with high efficiency.

The role of pulse length in target poisoning during reactive HiPIMS: application to amorphous HfO2

In conventional reactive magnetron sputtering, target poisoning frequently leads to an instability that requires the reactive gas flow rate to be actively regulated to maintain a constant composition of the deposited layers. Here we demonstrate that the pulse length in high power impulse magnetron sputtering (HiPIMS) is important for determining the surface conditions on the target that lead to poisoning. By increasing the pulse length, a smooth transition can be achieved from a poisoned target condition (short pulses) to a quasi-metallic target condition (long pulses). Appropriate selection of pulse length eliminates the need for active regulation, enabling stable reactive magnetron sputter deposition of stoichiometric amorphous hafnium oxide (HfO2) from a Hf target. A model is presented for the reactive HiPIMS process in which the target operates in a partially poisoned mode with a distribution of oxide on its surface that depends on the pulse length.

The Influences of Oxygen Content on Microstructures and Optical Properties of Al<sub>2</sub>O<sub>3</sub> Films Deposited by Oxygen Ion Beam Assisted Pulse Reactive Magnetron Sputtering

Al2O3 films have been deposited at room temperature on polyimide substrates using oxygen ion beam assisted pulse reactive magnetron sputtering system in which aluminium sputtering is simultaneous with oxygen ion beam irradiation. A set of samples were prepared at different oxygen content and film characterizations have been carried out using X-ray diffraction (XRD) for film crystallization, atomic force microscopy (AFM) for surface morphology, and X-ray photoelectron spectroscopy (XPS) for elemental composition measurements and chemical bonding states. The films are smoother and near stoichiometric aluminum oxide as oxygen content increases up to 86%. All films are kept in amorphous structure. The optical properties of the films showed sensitive with oxygen content. Transparent films of refractive index 1.63 are obtained with a deposition rate as high as 70.3 nm/min by 86% oxygen ion beam assisted, which is about 5 times than the films by conventional reactive magnetron sputtering.

Study of hybrid PVD–PECVD process of Ti sputtering in argon and acetylene

Hybrid PVD–PECVD process of target sputtering in hydrocarbon containing atmosphere combines aspects of both conventional reactive magnetron sputtering (PVD) and plasma enhanced chemical vapour deposition (PECVD). Such process is being typically used for deposition of metal carbides embedded in hydrogenated carbon matrix. Compared to the conventional co-sputtering of metal and carbon targets, in the hybrid deposition process the source of the carbon is dissociated hydrocarbon vapour in plasma. The aim of this paper is to study the extent of similarities or differences between this hybrid process and the conventional reactive magnetron sputtering. We have chosen the sputtering of titanium target in acetylene containing atmosphere as a representative of the hybrid processes. We focused on experimental measurements of the hybrid PVD–PECVD process behaviour, the time necessary for the process to achieve steady-state conditions and basic modelling of the process.

Stress and texture in HIPIMS TiN thin films

Titanium nitride (TiN) films in the thickness range of 0.013µm to 0.3µm were grown by high power impulse magnetron sputtering (HIPIMS) on silicon substrates in two deposition modes: a) the substrate was grounded and b) −125V bias was applied to the substrate. On the films we performed microstructure-, film texture- and film stress-analysis. The films deposited under −125V bias experienced a more energetic ion bombardment than the films deposited on grounded substrates. This difference in ion bombardment energy is reflected in the different microstructure. In contrast to previous results for TiN films grown by conventional reactive magnetron sputtering, we observe no major film stress gradient for increasing film thicknesses. We explain this observation from the absence of a 200-to-111 texture crossover during film growth.A moderate ion bombardment leads to TiN films with (111) texture, while an intense ion bombardment leads to films with (001) texture (Greene et al.; Appl. Phys. Lett. 67 (20) 2928–2930 (1995)). At the same time (001) oriented grains are much more susceptible to compressive stress generation by ion bombardment than (111) oriented grains.

Tribological Properties of CrN/AlN Films Produced by Reactive Magnetron Sputtering

The microstructure of CrN/AlN films, prepared by reactive magnetron sputtering under various conditions, was analyzed and related to the wear behavior of the films. One set of films was prepared by conventional reactive magnetron sputtering, a second set adding an extra amount of reactive gas to the initial Ar + N2 mixture and a third set adding an extra source of nitrogen near the substrate during sputtering. The samples were analyzed by scanning electron microscopy + energy dispersive microanalysis, high resolution scanning electron microscopy, atomic force microscopy, and x-ray diffraction. The results of the microstructural analysis revealed a clear difference in the morphology growth of the films when extra nitrogen was used compared to the conventionally prepared films. Formation of CrN was significantly faster than that of AlN. The most effective method to produce AlN was to introduce extra nitrogen. Pin-on-disk wear experiments were carried out in ambient air, to investigate the tribological behavior of the CrN/AlN system against a steel ball under dry conditions for various loads and a constant sliding speed. The results revealed that tribological properties of the layers improved unlike those of the untreated H13 steel. The friction behavior is closely related to the structure of the deposited films. The thicker CrN layer contributed to the higher load capacity of the coated steel when compared to the unmodified steel. However, wear life for the coating system was very short, denoted by the fairly poor adhesion of the film system to the steel substrate.

Ion-bombardment characteristics during deposition of TiN films using a grid-assisted magnetron system with enhanced plasma potential

Energy-resolved mass spectroscopy was used to investigate differences in ion-bombardment characteristics during conventional reactive magnetron sputtering of TiN films and their deposition using a grid-assisted magnetron system with anode at a high potential (up to 350 V relative to grounded chamber walls). Narrow ion energy distributions with a maximum corresponding to the ion energy close to 100 eV were obtained for the conventional magnetron deposition on a biased substrate ( V b=−100 V) in an 80%Ar+20%N 2 gas mixture at a pressure of 0.5 Pa. On the contrary, the energy distributions of ions bombarding a grounded substrate in the grid-assisted modified magnetron system with the grid potential V g=+100 V were broadened and extended to higher energies (up to 300 eV) under the same conditions. The change in the ion energy distributions is caused by increase in the plasma potential due to the high anode potential (approximately 320 V in this case). Simultaneously, the total ion flux to the substrate decreased 5.4 times compared with the conventional system. A combined effect of the enlarged kinetic energy of ions and their substantially reduced flux resulted in production of high-quality, densified TiN films with a smooth surface.

Growth of VO 2 films with metal-insulator transition on silicon substrates in inductively coupled plasma-assisted sputtering

Single-phase monoclinic vanadium dioxide (VO 2) films were grown on a Si(100) substrate using inductively coupled plasma (ICP)-assisted sputtering with an internal coil. The VO 2 film exhibited metal-insulator (M-I) transition at around 65 °C with three orders of change in resistivity, with a minimum hysteresis width of 2.2 °C. X-ray diffraction showed structural phase transition (SPT) from monoclinic to tetragonal rutile VO 2. For conventional reactive magnetron sputtering, vanadium oxides with excess oxygen (V 2O 5 and V 3O 7) could not be eliminated from stoichiometric VO 2. Single-phase monoclinic VO 2 growths that are densely filled with smaller crystal grains are important for achieving M-I transition with abrupt resistivity change.

Optical properties and deposition rate of sputtered Ta 2O 5 films deposited by ion-beam oxidation

Tantalum oxide films deposited by DC magnetron sputtering in the transition mode and ion-beam oxidation (IBO) at room temperature showed that the deposition rate of the IBO film was four times higher than that obtained by conventional reactive magnetron sputtering, and was correlated with the oxygen ratio, X O2=O 2/(O 2+Ar), in the ion beam. The results of Rutherford backscattering and X-ray photoelectron spectroscopy indicated that the films deposited by IBO with various ion energy had the same composition and chemical bonding; the refractive index changed with the ion energy. The Fourier transform infrared absorption spectra indicated that the films deposited by IBO had excellent moisture-resistant characteristics.

Phase formation and mechanical properties of alumina coatings prepared at substrate temperatures less than 500 °C by ionized and conventional sputtering

Investigations concerning the microstructure and mechanical properties of alumina coatings have been performed. Alumina coatings have been deposited by both ionized reactive magnetron sputtering (IMS) and conventional reactive magnetron sputtering (CMS) in an argon/ oxygen discharge onto stainless-steel coated silicon substrates. X-Ray diffraction (XRD) was used for the phase analysis, and nanoindenta tion was used to evaluate the mechanical properties. Substrate temperature during deposition was <500 °C, which is the technologically interesting temperature range to coat temperature sensitive substrates such as tool steels. The phase transformation temperatures from amorphous to κ-alumina containing films was found to be between 430 °C and 472 °C, and the transition temperature was lower for higher ion currents. A film containing a mixture of κ- and θ-alumina phases was grown at 430 °C. The crystalline film hardness was 22 ± 1 GPa. Films grown at the same temperature by conventional magnetron sputtering were X-ray amorphous, and the hardness was found to be strong function of the substrate temperature.

Heteroepitaxial growth of InN on AlN-nucleated (00.1) sapphire by ultrahigh vacuum electron cyclotron resonance-assisted reactive magnetron sputtering

A novel deposition technique, ultrahigh vacuum electron cyclotron resonance (ECR)-assisted reactive magnetron sputtering, has been developed for the preparation of group IIIA nitride thin films. In initial experiments, thin films of the semiconductor InN have been deposited on AlN-seeded (00.1) sapphire substrates, and the properties of these films studied as a function of growth temperature. Comparison to InN thin films grown by conventional reactive magnetron sputtering shows enhanced Hall mobilities (from about 50 to over 80 cm2/V s), a decreased carrier concentration (by about a factor of 2), an increased optical band gap, and an apparent reduction in homogeneous strain that is in part due to film relaxation induced by the ECR beam and in part to enhanced nitrogen content and more nearly stoichiometric films.

ECR-Assisted Reactive Magnetron Sputtering of InN

ABSTRACTThe growth of high-quality thin films of the Group IIIA nitrides is exceedingly difficult given their propensity for nonstoichiometry and the lack of suitable substrates for either homoepitaxial or heteroepitaxial growth. A novel deposition technique, ultrahigh vacuum electron cyclotron resonance-assisted reactive magnetron sputtering, has been developed for the preparation of Group IIIA nitride thin films. Thus far, thin films of the semiconductor InN have been deposited on AlN-seeded (00.1) sapphire substrates, and the properties (structural, morphology, and electrical transport) of these films studied as a function of growth temperature. Comparison to InN thin films grown by conventional reactive magnetron sputtering shows enhanced Hall mobilities (from about 50 to over 100 cm2/V-sec), a decreased carrier concentration (by about a factor of 2–3), an increased optical bandgap, and an apparent reduction in homogeneous strain that is in part to be due to film relaxation induced by the ECR beam and in part to enhanced nitrogen content and more nearly stoichiometric films.

High-rate aluminum oxide deposition by MetaModeTM reactive sputtering

MetaModeTM reactive sputtering was employed to produce optical quality aluminum oxide films at rates an order of magnitude higher than those possible with conventional reactive magnetron sputtering. System pressure, reactive-to-nonreactive gas flow ratio, and ion-source current density were varied to investigate their effects on rate, process stability, and film properties. It was found that the coatings deposited at a reduced pressure (0.27 Pa) produced dense, water-free coatings without compromising optical quality or deposition rate.