DC Magnetron Sputtering Source Research Articles

Energy-dependent film growth of Cu and NiTi from a tilted DC magnetron sputtering source determined by calorimetric probe analysis

Plasma-based processes are key applications in microsystems technology and are mainly used for the deposition and modification of thin films. A strong dependence on used equipment and materials can easily affect plasma processes and results in many differences of process characteristics like energy flow and deposition rates. For a deeper understanding of inclined magnetron-deposited thin films, a passive thermal probe was used to investigate the correlation between the film growth of two commonly used metallic target materials (Cu and Ni 46.8/Ti 53.2) and the energy flow from the plasma to the substrate. The special design of the sputtering system with a fixed angle of 45° between targets and substrate allows homogeneous coating of 200mm wafers with 100mm targets. The passive thermal probe measurements were performed radially across the substrate area for two different magnetron positions. Complementary surface and cross-sectional analysis of the deposited layers by atomic force microscopy, focused ion beam technique, and fracture edge analysis by scanning electron microscopy were performed on thin film samples on silicon substrate to investigate the growth rate and structure of the films. The films deposited in these experiments exhibit randomly oriented crystalline grains and heavily position-dependent change in surface topography and morphology from compact films to columnar growth, for Cu and NiTi respectively.

Experimentally unraveling the energy flux originating from a DC magnetron sputtering source

We present investigations of the energy flux in DC magnetron sputtering for 15 different target-gas combinations. The utilized gases were Ar, Kr and He which were studied using targets made of Ag, Al, Cu, Ti and W. The effect of parameter variations (distance, pressure and discharge power) was investigated by calorimetric measurements utilizing a passive thermal probe. For the variation of discharge power, supplementary measurements of plasma parameters and deposition rate were performed using a planar Langmuir probe and a quartz crystal microbalance. The obtained results were used to gain better insight into the different contributions to the integral energy flux. The measurements illustrate clearly that, depending on the target material and on the target gas combination, the main mechanisms generating the energy flux can vary dramatically. For small gas-target mass ratios, reflected neutrals were identified as the main contribution of the energy flux while for combinations with high sputter yield, condensation and kinetic impact of sputtered particles were found to be the most relevant. For thermally poor conducting targets as in the case of titanium, the target can heat up significantly resulting in a strong energy flux from heat radiation which dominates the otherwise modest energy flux.

The Relationship Between Characteristics of DLC Film and Electron Temperature Measured by Optical Emission Spectroscopy

Electron temperatures in Ne or Ar plasma produced by a dc magnetron sputtering source were measured by 2-D optical emission spectroscopy using a charge-coupled device camera. In addition, diamond-like carbon (DLC) films were prepared on glass plates using the same sputtering equipment. When increasing dc target current between 0.5 and 2.5 A, we observed a change in Raman spectra accompanied by increases in electron density and electron temperature. In Ar plasmas with a lower pressure and a higher target current, we obtained relatively hard DLC films, which is consistent with the change in the electron temperature.

The influence of target erosion on the mass spectra of clusters formed in the planar DC magnetron sputtering source

The present paper reports on target erosion as one of the crucial parameters influencing the cluster size distribution. Size distributions of nanosized Cu clusters produced by a DC magnetron sputtering source during the lifetime of several different targets were monitored using a quadrupole mass filter. It is indicated that, during the target lifetime, cluster size distribution continuously shifts towards larger cluster sizes and becomes broader. After a certain operation time the cluster size distribution changes abruptly and the cluster formation is stopped. This happens much earlier than the point at which the erosion groove depth reaches the target thickness. It is suggested that a change in the mass spectra during the target lifetime is caused by the variation of the free metal atom density in the aggregation region. This may be due to the alteration of the sputtering yield. It is shown that the variation of the mass spectra correlates with the angular dependence of the sputtering yield.

Mass Spectrometric Investigations of Nano‐Size Cluster Ions Produced by High Pressure Magnetron Sputtering

AbstractA comparison of quadrupole mass spectrometric (QMS) and transmission electron microscopic (TEM) characterization of silver nano‐cluster deposition produced by a nano‐cluster source consisting of a planar DC magnetron sputter source in a high pressure gas aggregation chamber is presented and discussed. Cluster sizes and size distributions detected by the two different techniques are compared and the differences are discussed. The effects of He to Ar ratio, gas flow and magnetron power on the cluster size distribution are evaluated. The influence of the target erosion and aging effects are mentioned, too (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Estimation of Thickness Ratio of Bi-Layer TiNi to Enhance Shape Memory Behavior

Shape memory thin films deposited by sputtering are attractive candidates for micro-electro-mechanical-system (MEMS) because of their large deformation and strong recovery force. In the present study Ni-Ti thin films have been deposited on NaCl substrates by DC magnetron sputtering source fitted with an 80mm diameter alloy target. In order to obtain a variety of film compositions, several discs of alloy target, which prepared in vacuum arc remelting (VAR), were used. Three types of thin films have been deposited; Ti and Ni-rich thin films were separately deposited on NaCl substrate and also a composite layer of Ni45Ti50Cu5 and Ni-rich. The as deposited Ni-Ti thin films were crystallized to change the amorphous structure to a nanostructured material to characterize shape memory and superelastic behaviors. The effect of composition on film structure and mechanical behavior was studied by using X-ray diffraction (XRD) and nanoindentation. The results of thin films behavior were used to calculate the thickness ratio of be-layer composite NiTi to obtain enhanced shape memory behavior.

Investigation of the Formation Mechanisms of Pd Nanoclusters Produced Using a Magnetron Sputtering Source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters’ size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters’ size distribution on various source parameters, such as the inert gas flow rate, and aggregation length have been investigated in details. This work demonstrates the ability of tuning the palladium nanoclusters’ size by proper optimization of the source operation conditions.

Residual stress in polytetrafluoroethylene-metal nanocomposite films prepared by magnetron sputtering

In the present research we have evaluated residual stress as well as thermal stability of polytetrafluoroethylene (PTFE) and PTFE-based silver (Ag) nanocomposite films fabricated by dual magnetron sputtering. We used a RF magnetron system for sputtering PTFE, and a DC magnetron sputter source for metal. We have demonstrated that thin nanocomposite films of Ag/sputtered PTFE (thickness 800 to 1100 nm, Ag concentration 3.5 to 24.5%) deposited on silicon are stressed (6.24 to 12.2 MPa). The residual stress depends on the concentration of the nanoparticles. Pure sputter deposited PTFE films are under a small tensile stress, which becomes increasingly more compressive upon increasing the filling factor of the metallic nanoparticles. Depending on the concentration of nanoparticles, the residual stress is determined by a thermal component that is sensitive to temperature variation, even in the range of room temperature. In the evaluation of the thermal response of the nanocomposite-silicon system, both the changes in the thermal expansion coefficient as well as the elastic modulus of the nanocomposite with the concentration should be taken into account.

Fabrication of size-selected Pd nanoclusters using a magnetron plasma sputtering source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. Plasma sputtering vaporizes the target’s material forming nanoclusters by inert gas condensation. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters’ size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters’ size distribution on various source parameters, such as the sputtering discharge power, inert gas flow rate, and aggregation length have been investigated. This work demonstrates the ability of tuning the palladium nanoclusters’ size by proper optimization of the source operation conditions. The experimental nanocluster sizes are compared with a theoretical model that reveals the growth of large nanoclusters from “embryos” by a two-body collision. The model is valid for a specific range of deposition parameters (low inert gas flow rates and aggregation lengths equal or below 70 mm).

Low-temperature vapour–liquid–solid (VLS) growth of vertically aligned silicon oxidenanowires using concurrent ion bombardment

Vertically aligned silicon oxide nanowires can be synthesized over a large area by alow-temperature, ion-enhanced, reactive vapour–liquid–solid (VLS) method. Synthesis ofthese randomly ordered arrays begins with a thin indium film deposited on a Si orSiO2 surface. At theprocessing temperature of 190 °C, the indium film becomes a self-organized seed layer of molten droplets, receiving atomicsilicon from a DC magnetron sputtering source rather than from the gaseous precursorsused in conventional VLS growth. Simultaneous vigorous ion bombardment aligns theobjects vertically and expedites mixing of oxygen and silicon into the indium. Silicon oxideprecipitates from each droplet in the form of multiple thin strands having diameters assmall as 5 nm. These strands form a single loose bundle growing normal to the surface,eventually consolidating to form one nanowire. The vertical rate of growth can reach300 nm min−1 in an environment containing argon, hydrogen, and traces of water vapour. This paperdiscusses the physical and chemical factors leading to the formation of the nanostructures.It also demonstrates how the shape of the resulting nanostructures can be furthercontrolled by sputtering, during both VLS growth and post-VLS processing. Keytechnological advantages of the developed process are nanowire growth at low substratetemperatures and the ability to form aligned nanostructure arrays, without the use oflithography or templates, on any substrate onto which a thin silicon film can be deposited.

Processes involved in the formation of silver clusters on silicon surface

We analyze scanning electron microscopy measurements for structures formed in the deposition of solid silver clusters onto a silicon(100) substrate and consider theoretical models of cluster evolution onto a surface as a result of diffusion and formation of aggregates of merged clusters. Scanning electron microscopy (SEM) data are presented in addition to energy dispersive X-ray spectrometry (EDX) measurements of the these films. Solid silver clusters are produced by a DC magnetron sputtering source with a quadrupole filter for selection of cluster sizes (4.1 and 5.6 nm or 1900 and 5000 atoms per cluster in this experiment); the energy of cluster deposition is 0.7 eV/atom. Rapid thermal annealing of the grown films allows analysis of their behavior at high temperatures. The results exhibit formation of cluster aggregates via the diffusion of deposited solid clusters along the surface; an aggregate consists of up to hundreds of individual clusters. This process is essentially described by the diffusion-limited aggregation (DLA) model, and thus a grown porous film consists of cluster aggregates joined by bridges. Subsequent annealing of this film leads to its melting at temperatures lower than to the melting point of bulk silver. Analysis of evaporation of this film at higher temperatures gives a binding energy in bulk silver of ɛ0= (2.74 ± 0.03) eV/atom.

Characteristic of silver doped DLC films on surface properties and protein adsorption

Ag-incorporated diamond-like carbon (DLC) films were prepared on Si substrate using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a silver DC magnetron sputter source. Ag was selected due to their potential values of biomaterial. The concentration of Ag in the films was varied from 0.1 to 9.7 at.% by controlling the fraction of Ar in the reaction gas mixture with benzene. In order to understand the influence of incorporated Ag on wettability, the surface energy and the protein adsorption as an indirect haemo-compatibility were measured. The surface energy of the Ag-incorporated DLC film decreased gradually with the increase of the Ag concentration. The haemo-compatibility was examined by the adsorption ratio of albumin/fibrinogen as an indirect method and improved with the increase of Ag concentration. The surface and biological behaviors of the films will be discussed in terms of the atomic bond characteristic and microstructure induced by Ag incorporation. Our results demonstrate that the Ag-incorporated DLC films are potentially useful as biomedical devices having good haemo-compatibility and hydrophobic characteristics.

Structure and mechanical properties of Ag-incorporated DLC films prepared by a hybrid ion beam deposition system

Ag-incorporated diamond-like carbon films were prepared on Si(100) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a silver DC magnetron sputter source. The Ag concentration in the films was controlled by changing the fraction of Ar in the Ar and benzene reaction gas. The chemical composition, microstructure, atomic bond structure, and mechanical properties were investigated for Ag concentrations ranging from 0 to 9.7 at.%. When the Ag concentration was 0.1 at.%, the Ag atoms were fully dissolved in the amorphous carbon matrix without forming any second phase. Amorphous and crystalline silver particles appeared when the Ag concentration was 1.7 and > 6.8 at.%, respectively. It was found that the hardness was not sensitive to the Ag concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated Ag atoms. The mechanical properties are discussed in terms of the changes in the microstructure and atomic bond structure induced by Ag incorporation.

Structure and mechanical properties of W incorporated diamond-like carbon films prepared by a hybrid ion beam deposition technique

W incorporated diamond-like carbon films were prepared on silicon(1 0 0) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a tungsten DC magnetron sputter source. The W concentration in the films was controlled by changing the fraction of Ar in the Ar and C 6H 6 reaction gas. The chemical composition, atomic bond structure, and mechanical properties were investigated for W concentrations ranging from 0 to 8.6 at.%. When the W concentration was <2.8 at.%, the W atoms were dissolved in the amorphous carbon matrix without forming a WC 1− x phase. Amorphous and crystalline WC 1− x nano-particles appeared when the W concentration was >2.8 and >3.6 at.%, respectively. It was found that the hardness and elastic modulus were not sensitive to the W concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated W atoms. The change in mechanical properties is discussed in terms of the microstructural changes induced by W incorporation.

Spatial distribution of the velocity distribution function of Fe atoms in a magnetron sputtering plasma source

We examined the spatial distribution of the velocity distribution function of Fe atoms in a conventional dc magnetron sputtering source by laser-induced fluorescence (LIF) imaging spectroscopy. By measuring the Doppler broadening of the excitation spectrum of LIF, we evaluated the velocity distribution function of Fe at many positions in the discharge space. By calculating the first- and second-order moments of the velocity distribution function, we obtained two-dimensional maps of the average velocity and the effective temperature in the r-z plane of the cylindrically symmetric magnetron discharge. The map of the average velocity clearly indicates that Fe atoms have fast velocity in the region adjacent to the target at a low discharge pressure such as 3 mTorr, while at a high gas pressure such as 20 mTorr, the average velocity of Fe atoms is almost zero in the entire discharge space. On the other hand, it has been found from the map of the effective temperature that the velocity distribution function observed at 3 mTorr has a broad width corresponding to approximately 8×104K in the bright plasma near the target.

Rotating dust ring in an RF discharge coupled with a dc-magnetron sputter source. Experiment and simulation

During an experiment involving coating of dust grains trapped in an RF discharge using a sputtering dc-magnetron source, a rotating dust ring was observed and investigated. After the magnetron was switched on, the dust cloud levitating above the RF electrode formed a ring rotating as a rigid body. Langmuir probe diagnostics were used for the measurement of plasma density and potential. It was discovered that the coupling of the dc-magnetron source to the RF discharge causes steep radial gradients in electron density and plasma potential. The rotation of the dust ring is attributed to the azimuthal component of the ion drag force, which appears due to the azimuthal drift of the ions caused by crossed radial electric and axial magnetic fields. In order to get more insight into the mechanism of dust ring rotation, a Particle-in-Cell simulation of a rotating dust cloud was performed. The results of the experiment and simulation are presented and discussed.

Offset errors during kinetic ellipsometric measurements in light- intensive plasma discharges

During kinetic ellipsometric investigations in light-intensive plasma discharges, an offset error generally must be taken into consideration. The influence of an offset error on the ellipsometric angles Ψ and Δ is demonstrated, and possibilities for overcoming this problem are presented. Examples are given for deposition of titanium by a hollow cathode arc evaporation device and by a dc magnetron sputter source. Ellipsometric measurements were done with two ellipsometers: a monochromatic ellipsometer with a rotating analyzer and an ellipsometer with a photoelastic modulator.

Distribution of magnetic properties of Ni-Fe-Nb film sputtered by PE target

To fabricate a high performance double-layered medium, the underlayer should be satisfied not only good magnetic properties, but also good crystallinity and crystalline orientation in order to realize the homogenous and fine crystalline growth of Co-Cr recording layer. We have already proposed a new type target for a DC magnetron sputtering source to fabricate a tape medium continuously. The permalloy films sputtered by the new target show the good magnetic properties and crystallinity even at a high power. And so we investigate the application of this target to fabricating of the rigid disks. In this paper, we mention about the distribution of magnetic property of the Ni-Fe-Nb films sputtered by the new target, and examine the appropriate structure of this target.

Shape-memory properties in Ni-Ti sputter-deposited film

The objective of this research is to establish a shape-memory effect in sputter-deposited films of nickel titanium. The alloy, generically called nitinol, was prepared from sputtering targets in two different compositions. Films were deposited up to 10 μm in thickness on glass substrates using a dc magnetron sputtering source. The as-deposited films were amorphous in structure and did not exhibit a shape memory. The amorphous films were crystallized with a suitable annealing process, and the transformation properties were measured using differential scanning calorimetry. The crystallized films showed transition temperatures that were much lower than those of the parent material. X-ray diffraction patterns indicated that the films were not a single phase but showed evidence of a second phase. However, the annealed films demonstrated a strong shape-memory effect. Stress/strain measurements and physical manipulation were used to evaluate the shape recovery. These tests demonstrated sustained tensile stresses of up to 480 MPa in the high-temperature phase, and a characteristic plastic deformation in the low-temperature phase.

Electrical transport, optical properties, and structure of TiN films synthesized by low-energy ion assisted deposition

Thin films of TiN, covering a narrow range around stoichiometric composition, were synthesized by low-energy ion assisted growth at deposition temperatures TD=100, 300, 500, and 700 °C. The deposition apparatus consisted of an unbalanced dc magnetron sputter source which allowed high rate deposition from a titanium target with simultaneous bombardment of the growing film by a beam of mixed Ar+ and N+2 ion species at an ion-to-condensing atom arrival rate ratio of five. For each deposition temperature, films were prepared at various ion energies in the range Ei =2–100 eV. The presence of reactive N+2 ions and the effects of ion bombardment facilitate increased incorporation of nitrogen and decrease the overall defect density in the structure of TiN. Electrical transport properties of films were investigated by measurements of the temperature dependence of resistivity ρ(T) in the range T=4–300 K, and superconducting transition temperature Tc. These measurements were complemented by measurement of optical reflectance, x-ray diffraction, and scanning electron microscopy investigations to determine the structure and composition of films. Collectively the film properties have a strong dependence on ion energy and deposition temperature. Films deposited at optimum conditions (TD =500 °C and Ei =30–50 eV) possess a high degree of crystalline perfection with a strong (200) texture and a high optical reflectance (82% at λ=800 nm). These properties correlate with the following optimum electrical properties: room-temperature resistivity ρ300∼26 μΩ cm, resistivity ratio RR=2.13, temperature coefficient of resistivity TCR=2.43×10−3 K−1, and Tc =5.35 K. These results represent the best results yet reported for microcrystalline TiN films. The temperature dependence of resistivity has a normal-metal behavior and it obeys Matthiessen’s rule. The phonon contribution to resistivity at room temperature, ρthermal, is about 14 μΩ cm and is in agreement with that of single-crystal TiN. As the disorder in the structure of TiN increases, TCR is found to decrease and zero TCR is predicted for limiting values of resistivity ρ300=300–400 μΩ cm.