Plasma Sputtering Deposition Research Articles

Micro/nanotribology of ultra-thin hard amorphous carbon coatings using atomic force/friction force microscopy

Microscale scratch and wear resistance tests using an atomic force microscope have been conducted on ultra-thin hard amorphous carbon coatings, often called diamond-like carbon (DLC) coatings, deposited using filtered cathodic arc (FCA), direct ion beam (IB), electron cyclotron resonance plasma chemical vapour deposition (ECR-CVD) and sputter (SP) deposition processes. Coating thicknesses of 20, 10, 5 nm and, for the first time, 3.5 nm coatings, have been investigated. The objectives of the study were to identify the thinnest coating that exhibits good wear-resistance, to identify deposition processes that produced superior coatings for wear-resistance and to understand failure mechanisms of such ultra-thin coatings during wear. It was found that, in general, the thicker coatings exhibited better scratch/wear performance than thinner coatings due to their better load-carrying capacity as compared to the thinner coatings. At 20 nm, ECR-CVD and FCA coatings showed the best wear resistance. At 10 nm, ECR-CVD was the best, while IB coating showed the best wear resistance at 5 nm. Five nanometer coatings showed reasonable wear resistance, while 3.5 nm coatings showed extremely low load-carrying capacity, poor wear resistance and evidence of early coating delamination. Although IB and ECR-CVD 3.5 nm coatings showed some amount of wear resistance at low loads, it appears that the 3.5 nm coatings studied are infeasible for wear-resistant applications as of now.

Enhanced deposition rates in plasma sputter deposition

Langmuir probe and emission spectroscopic measurements are performed in a high frequency (100 MHz) argon plasma used for the sputter deposition process of thin films of palladium (dedicated to catalysis applications). The metal source is a helicoidal palladium wire which is negatively biased with respect to the plasma potential. This induces sputtering by the ions present in the plasma. The probe results show that the presence of the helicoidal wire in the chamber does not affect the total ion flux at the substrate location. However, as the bias voltage on the wire and/or the argon pressure are increased, a secondary direct current (DC) discharge is created inside the helicoidal wire which follows a Paschen-like law; the breakdown voltage is lower than in the case of a conventional Ar discharge, probably as a result of the presence of primary electrons generated by the main high frequency (HF) plasma. This second discharge is characterized by a strong flux peak inside the helicoidal wire, which probably arises from a hollow cathode type discharge. From emission spectroscopy and deposition analysis, it is shown that this secondary plasma causes an increase of the sputtered Pd atom number and, consequently, an enhanced deposition rate.

Chemical and morphological characterization of Pd aggregates grown by plasma sputter deposition

In this work, the synthesis of supported Pd aggregates by plasma sputter deposition is studied. A helicoidal metal wire is negatively biased with respect to the plasma potential, which results in sputtering of the metal by the argon ions present in the plasma. The wire bias voltage is one of the most important experimental parameters because it determines the ion flux bombarding the metal surface as well as the energy of these ions. Thus, it plays a major role in the sputtering process. In order to study this aspect, deposits have been synthesized at mbar argon pressure and 2 min deposition time, at various wire bias voltages from -100 to 0 V. The amount of Pd deposited is measured by x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS) analyses and is found to increase linearly with the wire bias voltage (in absolute value) from 0.2 to 1.4 equivalent monolayers. In this study, it appears that XPS analysis is not suitable for quantification in the particular case of small dispersed aggregates, certainly because of a geometrical effect (apparent roughness) in recorded XPS line intensities. Nevertheless, from the XPS Pd peak shift with decreasing coverages, morphological information can be obtained. In this manner, the presence of small aggregates on the substrate surface has been detected. The morphology is more precisely studied by grazing incidence small angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM) analyses. In the present metal coverage range, the deposits are composed of small ( nm) spaced-out spherical aggregates, well dispersed on the surface.

FMR, XRD and XHRTEM characterization of stresses in an epitaxial Ni–Cu film prepared on MgO(001) by d.c. biased plasma sputter deposition

Ferromagnetic resonance (FMR), X-ray reflection diffraction (XRD) and cross-sectional high-resolution transmission electron microscopy (XHRTEM) are applied to characterize the stresses of the d.c. biased plasma-sputter-deposited Ni 97Cu 3 films grown epitaxially on a MgO(001) substrate. The FMR study indicates that a homogeneously compressive intrinsic stress and an anisotropic planar stress are simultaneously induced in the film. The latter consists of the part induced during the film formation and the part originated from the magnetocrystalline anisotropy of the Ni–Cu crystal. The compressive stress in the film is also confirmed by the XRD study. The XHRTEM study reveals misfit dislocations generated in the Ni–Cu crystal at the MgO interface relaxing the strain energy due to the lattice mismatch between Ni 97Cu 3 and MgO crystals and locally induced lattice distortions. In conclusion the stress inside the film is compressive as a whole. © 1997 Elsevier Science S.A.

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering

We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH 3 gas ranging from 0.1 to 1.0 ppm is increasing.

Pt thin films prepared by low energy plasma sputtering

Platinum thin film has been prepared by low energy plasma sputtering deposition. Surface smoothness, stress in the film, crystal grain size and crystal orientation have been investigated for target voltages between 10 and 500 V. The effect of substrate temperature has also been studied. A minimum roughness of 1.1 nm was obtained with voltage of 20 or 30 V at room temperature. Auger analysis suggests that the deposition mechanism at 30 V is similar to the layer-by-layer (two-dimensional) deposition, while that at 100 V is significantly different. The formation of a very smooth surface is thought to be related to the layer-by-layer deposition process. The (111) oriented thin film was obtained at the target voltage of 30 V at room temperature.

イオンプレーティング法によるセラミックス薄膜に関する研究

This paper review recent research on synthesis of ceramics thin films with ion beam assisted deposition, electron cyclotron resonance plasma sputtering deposition and vacuum arc ion plating deposition method. These deposition method are generally applied to that technique in which deposition and simultaneous ion bombardment of a growing film surface are performed with a low-energy activated particles. The effects of the bombardment during deposition may result in either physical, structural change in the chemical reaction. Examples include improved adhesion, preferred crystal orientation, improved stoichiometry and synthesis of diamond and cubic BN at room temperature. There remain however, important items of study that have not yet received sufficient attention. One may be study in atomic level of these modifications caused by the ion bombardment during the nucleation stage of film growth.

Structural and electrical properties of NiCu films deposited onto MgO(001) by d.c. biased plasma sputter deposition

NiCu alloy films were deposited onto MgO(001) substrates at 230 °C by d.c. plasma sputtering at 2.7 kV and 8 mA in pure Ar gas using an Ni-10wt.%Cu alloy target. The deposition time was 15 or 30 min. A d.c. bias voltage V s ranging from 0 to −140 V was applied to the substrate during deposition. The structure, composition and electrical properties of the films were studied as a function of V s using cross-sectional transmission electron microscopy (XTEM) and X-ray photoelectron spectroscopy (XPS), and measurements of the temperature coefficient of electrical resistance (TCR) from −135 to −15 °C. The alloy films, which have the f.c.c. lattice of the components, are monocrystalline with the relationship NiCu(001) ∥ MgO(001) and NiCu[010] ∥ MgO[010] unless V sp = −110 V. The Cu content in the films decreases from 8 wt.% to 3 wt.% as V s increases from 0 to −140 V. The growth rate of the films and the value of TCR η (η > 0) depend on V s; the film thickness d for the films deposited for 30 min reaches 50 ± 1 nm at V s = 0 V and 74 ± 2 nm at V s = −140 V, while η for the films deposited for 30 min increases appreciably with increasing V s compared with the films deposited for 15 min, although η is highest at V s = −140 V for both cases.

Structure of gold-hydrocarbon composite thin films deposited using low-voltage plasma sputtering method

We have investigated the properties of gold metal/polymer composite thin films. These composite films are prepared by DC plasma sputter deposition using an argon and methane gas mixture. A high-purity gold metal was used as a sputtering target. Sputtered gold atoms do not make compounds with hydrocarbon in plasma, because gold is a non-reactive metal. Additionally, both plasma polymerization of the methane and deposition of the sputtered gold atoms appear on the substrate. Consequently, composite films are formed. Composite films can be changed from metallic to dielectric according to the preparation conditions. There are main 2 parameters, i.e., the sputtering voltage and the partial pressure of the methane. It is necessary that the sputtering voltage is low, under 300 V in this work, because bombardment of the high-energy particles occurs to suppress the polymer growth on the substrate. It is found that the desired structure and properties of the composite thin films can be obtained, by suitable adjustments of the partial pressure of the methane, at a sputtering voltage of 300 V.

Sputter Synthesis of Ferroelectric Films and Heterostructures

Ferroelectric films can display a wide range of dielectric, ferroelectric, piezoelectric, electrostrictive, and pyroelectric properties. The potential utilization of these properties in a new generation of devices has driven the intensive studies on the synthesis, characterization, and determination of processing-microstructure-property relationships of ferroelectric thin films during the last five years. In addition there has been an increased drive for integrating ferroelectric film-based heterostructures with different substrate materials to demonstrate numerous devices that exploit the dielectric, ferroelectric, piezoelectric, electrostrictive, and pyroelectric properties of these materials. For example the high dielectric permittivities of perovskite-type materials can be advantageously used in dynamic random-access memories (DRAMs), while the large values of switchable remanent polarization of ferroelectric materials are suitable for nonvolatile ferroelectric random-access memories (NVFRAMs).Various vapor-phase deposition techniques such as plasma and ion-beam sputter deposition (PSD and IBSD, respectively), pulsed laser-ablation deposition (PLAD), electron-beam or oven-induced evaporation for molecular-beam epitaxy (MBE), and chemical vapor deposition (CVD) have been applied to produce ferroelectric films and layered heterostructures. See References 4–7 for recent reviews. However, work is still necessary to optimize the techniques to produce device-quality films on large semiconductor substrates in a way that is fully compatible with existing semiconductor process technology. Therefore research efforts should be focused on the optimization of suitable process methods and on the investigation of processing-composition-microstructure property relationships. These efforts are the focus of this article with emphasis on PSD and IBSD techniques.

Partially reactive d.c. magnetron sputtering — a key to new understanding of reactive plasma sputter deposition?

This paper deals with reactive gas incorporation during d.c. magnetron sputtering under process conditions resulting in undersaturated films, defined as partially reactive. Besides a reactive gas incorporation via classic adsorption, a four-stepped reaction sequence is discussed consisting of: (1) ionization; (2) ion bombardment of the target and, simultaneously, formation of a coverage by plating; (3) removal of this coverage by sputtering; (4) condensation on the substrate. The reaction course is mirrored by simple macrokinetic rate equations as demonstrated with different reactive gases and a CrSi target. Because of the simplicity of the relationships, and a possibly wide transferability, it is considered that investigations into partially reactive d.c. magnetron depositions could become important also for more complex reaction conditions.

Kr incorporation in sputtered amorphous Si layers

Amorphous Si layers were grown by krypton plasma sputter deposition at 310 °C. By pulsation of the substrate potential between 0 and 50 eV, the Kr concentration in the layers could be varied to a maximum of 5.5 at. %. A model which describes trapping of inert gas atoms in the sputtered layer in terms of implantation and trapping, diffusion, growth, resputtering, and gas sputtering is presented. High-resolution electron microscopy, electrode-probe (x-ray) microanalysis, positron annihilation, Raman spectroscopy, Mössbauer spectroscopy, and bending and hardness measurements were performed on the deposited layers. It turns out that the ion assisted growth leads to a strong reduction of open volume defects. The experiments point to the presence of very small Kr agglomerates. From the Mössbauer experiments a lower limit of 250 K for the Debye temperature of the Kr agglomerates is derived. Molecular-dynamic simulations from which the Debye temperatures of Kr mono-, di-, and trimers in amorphous Si can be derived are presented. The simulations indicate the presence of predominantly Kr monomers and dimers.

Ferromagnetic resonance in Ni films produced by biased d.c. sputter deposition onto SiO2 and Si(100)

Ferromagnetic resonance measurements at the X-band were taken at room temperature mainly to investigate the mechanical properties of Ni films 180 nm thick prepared on both pure and SiO2-covered Si(100) substrates at 190 °C by biased d.c. plasma sputter deposition at 2.5 kV in Ar gas. A negative bias voltage Vs between 0 V and −80 V was applied to the substrates during deposition. The homogeneous intrinsic stress σi induced in the films is compressive (σi <0). The magnitude of σi depends on Vs. For the Ni/SiO2 system − σi has a maximum as Vs reaches about −30 V because the impurities are most strongly embedded in the film with incoming Ar particles. When − Vs is over 30 V the more energetic Ar particles contribute to a decrease in − σi through resputtering the impurities. For the Ni/Si system − σi, only increases monotonically with Vs, mainly owing to the peening effect. The anisotropic planar stress σu which is much smaller in magnitude than σi is also induced in the film for both systems. The origin of σu is not understood at present. Thus, the g-factor varies with Vs mainly in agreement with the dependence of σi on Vs for both systems.

Models and algorithms for three-dimensional topography simulation with SAMPLE-3D

Algorithms for general surface advancement, three-dimensional visibility, and convolution over a surface have been developed and coupled with physical models for pattern transfer. The resulting program, SAMPLE-3D, allows practical simulation of plasma etching and deposition processes on engineering workstations. The physical models are 3-D extensions of 2-D string and segment based models. The models include secondary effects, such as material density variations and damage enhanced etching. A general facet motion algorithm supports simple, isotropic, cosine-directional, and general surface orientation dependent processes. A 3-D grid of rectangular prismatic cells, which is updated by the advancing surface, contains an alternate topography representation for fast shadow and visibility calculation. The program is organized as a collection of modular functions for continued model and algorithm development. Guidelines for estimating CPU and memory requirements for various models and simulation cases are based on an analysis of the algorithms and data structures. Simple processes, such as lithography development, require 1-5 min of CPU time. Simulations involving integration over flux distributions, such as plasma etching and sputter deposition, require from 5-30 min for typical cases. Reflection or surface migration calculations require from 30-60 min. Physical memory of 4-32 megabytes is sufficient for many practical simulations. >

A Mössbauer Study on Solid Krypton Precipitates in Aluminium and Silicon

ABSTRACTMössbauer spectroscopy on the 9.4 keV transition in 83Kr is used to study inert gases in metals and semiconductors. An absorber was made by implanting 83Kr at 110 keV in Al foils to a total dose of 1.7· 1016 Kr cm−2, leading to the formation of small precipitates (bubbles). Spectra on the as-implanted sample were taken as a function of temperature for three 83RbI sources which differ in line shape due to a different water content. A model is presented to extract the absorber parameters from the spectra in a consistent way, in spite of the different sources used. The spectra of Kr bubbles in Al produced by high dose implantation show two components: a single line from Kr inside the bubble and a quadrupole split component from Kr at the Kr-Al interface. The total absorption area could be fitted very well assuming a simple Debye model, yielding a Debye temperature of ΘDT = 101(2) K. For the individual components we obtained Debye temperatures of ΘDQ = 98(6) K and ΘDS = 90(10) K. The isomer shift of the bulk fraction is significantly larger than that of a solid Kr layer at ambient pressure, reflecting the fact that the s-density increases under compression. The size of the precipitates can be estimated to be 1.5–1.8 nm. Thin KrSi films, produced by Kr plasma sputter deposition, were characterized using cross-sectional X-ray analysis. The results clearly show two different layers. Presumably, the film grows at first as c-Si with a low Kr concentration, but after having reached a certain critical thickness, further growth proceeds as a-Si with a high Kr concentration. For Mössbauer spectroscopy an absorber of 83KrSi was made by plasma deposition on an Al foil. The spectra can be fitted with a single line and a quadrupole component, both with isomer shifts much larger than found in the case of small Kr bubbles in Al. No change in the total absorbed area was observed from 4.2 to 200 K indicating a lower limit of 250 k for the Debye temperature. Both observations indicate that the Kr resides in very small clusters.

Preparation and Dielectric and Electrooptic Properties of Bi4Ti3O12 Films by Electron Cyclotron Resonance Plasma Sputtering Deposition

Polycrystalline and epitaxlal films of a layer-structured ferroelectric Bi4Ti3O12 in perovskite phases have been deposited on sapphire substrates by ECR plasma sputtering using a sintering ceramic target. The substrate temperature higher than 550°C is necessary to grow Bi4Ti3O12 films in the perovskite phase without post-thermal annealing. Bi4Ti3O12 films were epitaxially grown on C, A and R surfaces of a sapphire single crystal. Refractive indices of Bi4Ti3O12 films were determined from measurements of the Brewster angle, and the dielectric constant was measured at 1 kHz using an ADEX-221A LCR meter.

WNx Schottky diodes on plasma treated GaAs

The influence of the GaAs surface condition on the properties and thermal stability of WNx Schottky diodes on GaAs has been studied by performing in situ H2 and N2 plasma treatments just before the WNx sputter deposition. The WNx/GaAs contacts have been investigated by x-ray photoelectron spectroscopy, Rutherford backscattering, nuclear reaction analysis, secondary ion-mass spectroscopy, x-ray diffraction, and transmission electron microscope and correlated to electrical current-voltage and capacitance-voltage measurements. A strong correlation was found between the diode properties and the surface conditions, both for the as-deposited samples and for samples annealed in the range 700–850 °C. Poor rectifying properties were obtained for the plasma-cleaned diodes due to the cumulative effects of plasma cleaning and sputter deposition. After annealing, improved characteristics were generally found. The highest Schottky barrier height values φI-V=0.76 V, which were found for the H2 plasma treated diodes annealed at 800 °C, were almost independent of the WNx composition and sputtering conditions. The H2 treated samples also showed the smoothest WNx/GaAs interface. HCl cleaned and N2 treated surface also showed high-barrier height and small interfacial reactions after high-temperature annealing.

Thin silicon oxides grown by low-temperature rf plasma anodization and deposition

We have studied the low-temperature (&amp;lt;500 °C) growth and deposition of thin silicon oxides in an rf plasma system. Oxides were grown by plasma anodization, sputter deposition, and combinations of these two processes. The oxides were electrically characterized with high-frequency and low-frequency capacitance-voltage techniques and the quality was found to depend strongly on plasma process parameters. In particular, we found strong dependences on bias current, plasma potential, and oxygen partial pressure. Under presently optimal conditions we have fabricated oxides with oxide charge densities Qox&amp;lt;1×1011 charges/cm2, interface state densities Dss&amp;lt;2×1011 states/cm2/eV, and breakdown fields Eb&amp;gt;13 MV/cm. Finally, we have studied the reduction of fast surface states in the plasma oxides by rapid thermal annealing.

Monte Carlo simulation of thermalization process of sputtered particles

The transport process of sputtered particles in plasma sputter deposition was studied by computer simulation using the Monte Carlo method, with particular attention to the understanding of the thermalization process. Due consideration was taken of the momentum loss as well as of the energy loss of sputtered particles colliding with sputter gas molecules. The results clearly showed that with increasing target-substrate distance, the energy distribution of sputtered copper atoms arriving at the substrate shifts toward lower kinetic energies, but still contains a considerable fraction of high energy particles. In addition, it was found that the arrival rate of sputtered copper atoms at the substrate decreases exponentially with the target-substrate distance, while the return rate to the target first increases and then becomes constant. It was concluded that the present Monte Carlo simulation can be successfully used for a quantitative estimation of the transport process of sputtered particles.

Monte Carlo simulation of thermalization process of sputtered particles

The transport process of sputtered particles in plasma sputter deposition was studied by computer simulation using the Monte Carlo method, with particular attention to the understanding of the thermalization process. Due consideration was taken of the momentum loss as of the energy loss of sputtered particles colliding with sputter gas molecules. The results clearly showed that with increasing target-substrate distance, the energy distribution of sputtered copper atoms arriving at the substrate shifts toward lower kinetic energies, but still contains a considerable fraction of high energy particles. In addition, it was found that the arrival rate of sputtered copper atoms at the substrate decreases exponentially with the target-substrate distance, while the return rate to the target first increases and then becomes constant. It was concluded that the present Monte Carlo simulation can be successfully used for a quantitative estimation of the transport process of sputtered particles.