Karol Macak

Ionized sputter deposition using an extremely high plasma density pulsed magnetron discharge

Time resolved plasma probe measurements of a novel high power density pulsed plasma discharge are presented. Extreme peak power densities in the pulse (on the order of several kW cm−2) result in a very dense plasma with substrate ionic flux densities of up to 1 A cm−2 at source-to-substrate distances of several cm and at a pressure of 0.13 Pa (1 mTorr). The pulse duration was ∼100 μs with a pulse repetition frequency of 50 Hz. The plasma consists of metallic and inert gas ions, as determined from time resolved Langmuir probe measurements and in situ optical emission spectroscopy data. It was found that the plasma composition at the beginning of the pulse was dominated by Ar ions. As time elapsed metal ions were detected and finally dominated the ion composition. The effect of the process parameters on the temporal development of the ionic fluxes is discussed. The ionized portion of the sputtered metal flux was found to have an average velocity of 2500 m s−1 at 6 cm distance from the source, which conforms...

Influence of plasma parameters on the growth and properties of magnetron sputtered CNx thin films

Carbon nitride CNx thin films were grown by unbalanced dc magnetron sputtering from a graphite target in a pure N2 discharge, and with the substrate temperature Ts kept between 100 and 550 °C. A solenoid coil positioned in the vicinity of the substrate was used to support the magnetic field of the magnetron, so that the plasma could be increased near the substrate. By varying the coil current and gas pressure, the energy distribution and fluxes of N2+ ions and C neutrals could be varied independently of each other over a wide range. An array of Langmuir probes in the substrate position was used to monitor the radial ion flux distribution over the 75-mm-diam substrate, while the flux and energy distribution of neutrals was estimated through Monte Carlo simulations. The structure, surface roughness, and mechanical response of the films are found to be strongly dependent on the substrate temperature, and the fluxes and energies of the deposited particles. By controlling the process parameters, the film struc...

Hydrogen uptake in alumina thin films synthesized from an aluminum plasma stream in an oxygen ambient

We describe the hydrogen uptake during the synthesis of alumina films from H2O present in the high vacuum gas background. The hydrogen concentration in the films was determined by the 1H(15N,αγ)12C nuclear resonance reaction. Furthermore, we show the presence of hydrogen ions in the plasma stream by time-of-flight mass spectrometry. The hydrogen content increased in both the film and the plasma stream, as the oxygen partial pressure was increased. On the basis of these measurements and thermodynamic considerations, we suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film. The large scatter in the data reported in the literature for refractive index and chemical stability of alumina thin films can be explained on the basis of the suggested aluminum oxide hydroxide formation.

High rate reactive dc magnetron sputter deposition of Al2O3 films

Aluminum oxide films were produced by reactive dc magnetron sputtering of Al in Ar+O2. The composition of the films was characterized by Rutherford backscattering measurements. Stoichiometric films possessed excellent optical properties with a refractive index of ∼1.6 for visible and near-infrared light. It was possible to produce stoichiometric films while keeping the target in the metallic mode of operation; the resulting deposition rate was 23 nm min−1, as compared to 0.95 nm min−1 for films grown from an oxidized target. An O/Al arrival rate ratio exceeding ∼17 was required for stoichiometric films to be grown at room temperature. The success of the present high-rate deposition strategy hinges on the use of a suitable deposition system geometry — including a large target-to-substrate distance and a small target size — and on the use of sufficient Ar pressure. Monte Carlo simulations are presented; they can be reconciled with our empirical data.

Epitaxial growth of W-doped VO2/V2O3 multilayer on α-Al2O3(110) by reactive magnetron sputtering

Multilayer epitaxy with a W-VO2 top layer over a bottom layer of which the crystal phase depends on the starting oxygen flow, was done on a-Al2O3(110) by reactively sputtering a V-W (1.6 at.% wt.) ...

Monte Carlo simulations of the transport of sputtered particles

Program SPATS models the transport of neutral particles during magnetron sputtering deposition. The 3D Monte Carlo simulation provides information about spatial distribution of the fluxes, density of the sputtered particles in the chamber glow discharge area, and kinetic energy distribution of the arrival flux. Collision events are modelled by scattering in Biersacks potential, Lennard-Jones potential, or by binary hard sphere collision approximation. The code has an interface for Monte Carlo TRIM simulated results of the sputtered particles.

Growth and characterization of epitaxial films of tungsten-doped vanadium oxides on sapphire (110) by reactive magnetron sputtering

Epitaxial films of W-doped vanadium oxides including W–V2O3, W–VO2 and W–V2O5 were deposited on sapphire (110) by reactive magnetron sputtering of a V–W (1.6 at. % W) alloy target in a range of oxygen partial flows. The deposited films were characterized by x-ray diffraction (XRD), Rutherford backscattering spectrometry, atomic force microscopy and resistance-temperature measurement. The W-to-V ratio in the oxide films showed values higher than that in the target, and the ratio increased with increasing oxygen flows. With precise control of the oxygen partial, flow, not only the W–V2O3, W–VO2 and W–V2O5, but also a series of epitaxial films with lattice parameters varying between those of W–V2O3 and W–VO2 were formed. It was found from an XRD pole figure study that the W–VO2 exhibited a triple-domain structure with the three domains correlated by 120° in the in-plane orientation. The W–VO2 epitaxial films clearly showed a semiconductor-to-metal phase transition with a reduced Tc by 23 °C/at. % W, whereas ...

Reactive d.c. magnetron sputter deposited Al2O3 films: large-area coatings for industrial applications

Stoichiometric Al2O3 films are produced with a pure Al source in the metallic state in an O2+Ar gas mixture using reactive d.c. magnetron sputtering. Substrates as large as 70×100 cm2 are uniformly coated at room temperature while moving in front of the cathode. The key to the success lies in utilizing a sufficiently high working gas pressure and a sufficiently large source-to-substrate distance. Monte Carlo simulations are used to estimate the latter. The process is extremely stable, and despite the large target size, no arcing is detected.

MODELING OF THE DEPOSITION OF STOICHIOMETRIC AL2O3 USING NONARCING DIRECT CURRENT MAGNETRON SPUTTERING

dc sputter deposition of stoichiometric Al2O3 is usually difficult due to the formation of an oxidized layer on the target surface, which reduces the deposition rate drastically and causes charge buildup and arcing at the target. To avoid this situation the arrival rate ratio O2/Al must be high enough at the substrate position that a stoichiometric film can form but low enough at the target that a conducting target surface is maintained. We have utilized Monte Carlo simulations to estimate the flux distribution of sputtered particles for different geometries. These results, supplemented by Bergs’ standard steady state model for the reactive sputtering process, made it possible to predict the composition at different surfaces in the processing chamber. Experimental studies were carried out for several different target-to-substrate distances and a range of sputtering gas pressures. The results show that the process can be tailored to achieve stoichiometric Al2O3 at the substrates while keeping the target in...

Mechanisms for reactive DC magnetron sputtering of elements with different atomic masses : Large area coatings of Al oxide and W oxide

Stoichiometric Al and W oxide films are prepared with high stability from the metallic state of the cathodes using conventional reactive DC magnetron sputtering on an industrial prototype scale. While for the Al, increased target power is a trivial way to increase growth rates, W oxide sputtering of optically functional films with sufficiently amorphous structure is severely limited by the effect of gas rarefaction at high powers. Choosing an appropriate working gas pressure and a source-to-substrate distance, which facilitates the gas scattering allows the deposition of homogeneous stoichiometric tungsten oxide films in a stable condition with a relatively high discharge current. Optimization of the process parameters with respect to film properties and efficiency of the deposition process is discussed.