Electron Cyclotron Resonance Microwave Research Articles

Plasma-enhanced chemical vapor deposition of SiO2 from a Si(CH3)3Cl precursor and mixtures Ar/O2 as plasma gas

Silicon dioxide thin films have been prepared at room temperature by remote plasma-enhanced chemical vapor deposition in a downstream reactor by using Si(CH3)3Cl as a volatile precursor and a microwave electron cyclotron resonance external source. Experiments are done at constant pressure by changing the relative amount of Ar species R in the plasma gas. The aim was to obtain thin films with low density and, therefore, low refractive index. Characterization of the species of the plasma is carried out by optical emission spectroscopy. The changes of the plasma conditions are correlated with the growing rate and microstructure of the films, the latter determined by atomic force microscopy and infrared spectroscopy. It is found that the growing rate of the films decreases and their roughness increases as R increases. The optical properties of SiO2 thin films are analyzed by optical ellipsometry. A decrease in the refractive index is found for the films grown with high values of R. The possible routes for activation of the precursor and the formation of the SiO2 thin films are discussed.

Preparation of Diamond-Like carbon Films in methane byElectron Cyclotron Resonance Microwave Plasma Source Ion Implantation

Diamond-like carbon (DLC) films were prepared on Si (100) substrates byion implantation from an electron cyclotron resonance microwave plasmasource. During the implantation, 650 W microwave power was used toproduce discharge plasma with methane as working gas, and -20 kV voltagepulses were applied to the substrate holder to accelerate ions in theplasma. Confocal Raman spectra confirmed the DLC characteristics of thefilms. Fourier-transform infrared characterization indicates that theDLC films were composed of sp3 and sp2 carbon-bondedhydrogen. The hardness of the films was evaluated with a NanoIndenter-XP System. The result shows that the highest hardnessvalue was 14.6 GPa. The surface rms roughness of the films was as lowas 0.104 nm measured with an atomic force microscope. The frictioncoefficient of the films was checked using a ball-on-diskmicrotribometer. The average friction coefficient is approximately 0.122.

Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

An internal transport barrier (ITB) was observed in the electron temperature profile in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] with a centrally focused intense electron cyclotron resonance microwave heating. Inside the ITB the core electron transport was improved, and a high electron temperature, exceeding 10 keV in a low density, was achieved in a collisionless regime. The formation of the electron-ITB is correlated with the neoclassical electron root with a strong radial electric field determined by the neoclassical ambipolar flux. The direction of the tangentially injected beam-driven current has an influence on the electron-ITB formation. For the counter-injected target plasma, a steeper temperature gradient, than that for the co-injected one, was observed. As for the ion temperature, high-power NBI (neutral beam injection) heating of 9 MW has realized a central ion temperature of 5 keV with neon injection. By introducing neon gas, the NBI absorption power was increased in low-density plasmas and the direct ion heating power was much enhanced with a reduced number of ions, compared with hydrogen plasmas.

Plasma-enhanced deposition of hard silicon nitride-like coatings from hexamethyldisiloxane and ammonia

Hard silicon nitride-like coatings have been grown in a high-density microwave electron cyclotron resonance discharge, using hexamethyldisiloxane (HMDSO) as the deposition precursor and ammonia as the reactive gas. Statistical experiment design methodology was used to investigate the effects of microwave power and NH 3/HMDSO flow-rate ratio on the growth rate, elastic modulus and hardness of the plasma-grown coatings. The films deposited are hard, colorless and transparent, with growth rates of up to 0.5 μm/min. Films lasted 745–840 h in an ASTM B117 salt-fog corrosion test. X-Ray photoelectron spectroscopic analyses showed the coating composition to be SiC x O y N z , with significant carbon and up to 13.7 at.% nitrogen concentration. While not stoichiometric Si 3N 4, coatings grown at high microwave power and high NH 3/HMDSO flow ratios had an elastic modulus of 176 GPa and hardness of 12.2 GPa, comparable to values reported for thermally grown silicon nitride.

Preparation and characterization of amorphous GaF 3 and GaF 3–BaF 2 thin films by ECR microwave plasma-enhanced CVD

Amorphous GaF 3 and GaF 3–BaF 2 thin films were prepared by electron cyclotron resonance microwave plasma-enhanced chemical vapor deposition. Metal β-diketonates and a NF 3 gas were used as starting materials and a fluorinating reagent, respectively. Single crystals of CaF 2(1 1 1) were employed as substrates. Almost contaminant-free and amorphous GaF 3 and GaF 3–BaF 2 films were obtained on the substrates kept at 300 °C at the deposition rates of 0.8 μm h −1 and 1.1–1.8 μm h −1, respectively. In amorphous GaF 3–BaF 2 films, optical propagation was detected at one or two transverse electric modes. The refractive indices of GaF 3–BaF 2 thin films increased with the BaF 2 content. Based on the measured refractive indices, moreover, the synthesis condition of single-mode planar optical waveguides were determined. Consequently, the optimum thickness of amorphous GaF 3–BaF 2 thin film was estimated to be approximately 0.3–1.6 μm.

Adjustment of electron temperature in ECR microwave plasma

In glow discharge plasma used for processing of materials, the electron temperature affects directly reactive species determining results of plasma processing of materials. In this paper, the experiment results of adjustment of electron temperature ( T e) in an Electron Cyclotron Resonance (ECR) device in H 2 and H 2+CH 4 plasmas are given by two methods. One method to adjust T e is the grid method, by installing a floated or biased grid in the plasma; the T e can be increased or decreased. Another method is noble gases doped into the discharge gases; increasing noble gas concentration can decrease T e in a certain scale. The changes of species in plasma are inspected by the optical emission spectroscope and mass spectroscope when T e is dropped.

Blue photoluminescence of aSiOxNy films prepared by ECR-CVD

Amorphous silicon oxygen nitride (aSiOxNy) films are prepared by microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) method using 10% SiH4 in N2/O2 mixtures. The Fourier transform infrared absorption spectroscopy shows that the main bonding configuration of the films is SiO and SiN. If O2 is input, the dominant composition of the films is SiOx, while it is SiNx at zero O2 flow rate. A blue photoluminescence (PL) band at 460nm produced by 565eV laser excitation is observed at room temperature from these films, and the emission intensity increases with decreasing O2 flow rate. The blue PL for aSiOxNy films, mainly composed of aSiOx, comes from oxygen deficient defects in the SiOx matrix. For aSiOxNy films, mainly composed of aSiNx, its blue PL is due to the electronhole radiative recombination from the defect states in the SiNx matrix.

Mechanical and Tribological Properties of Diamond-Like Carbon Films Deposited by Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition

Mechanical and tribological properties of diamond-like carbon (DLC) films deposited by electron cyclotron resonance microwave plasma chemical vapor deposition were analyzed by nanoindentation, nanoscratch and ball-on-disk sliding tests. As the results, hardness and residual stress which depended on the substrate bias voltage had combined effects on the scratch resistance of the films. In sliding friction tests, the transferred layer on the surface of the counterpart accounts for the decrease of friction coefficient with increasing sliding distance. Atomic force microscopic images of the DLC films and the counterpart Si3N4 ball surfaces indicate that the sliding friction process could be treated as a periodical scratching process with many indenters.

Benzene flow rate effect on the properties of carbon films deposited on plasma nitrided steel using the MW/ECR PACVD process

Amorphous hydrogenated carbon a-c:H films often called DLC films were deposited on plasma nitrided layers of Z30C13 steel substrate using the Microwave Electron Cyclotron Resonance Plasma Assisted Chemical Vapour Deposition method with benzene/argon gas a precursor. The coatings were deposited on ferrite and (ε) Fe 2–3N at different temperatures: 623, 753 and 793 K for time intervals between 2 up to 120 min under different pressures ranging from 10 −3 to 10 −1 Pa. A wide range of thickness values of the amorphous carbon layers (0.4 up to 15 μm) was formed a function of the deposition conditions and precursors, when the bias voltage (−200V) and microwave power (300 W) were kept constant. However, pretreatments consisting in mechanical polishing down to a surface roughness Ra< 0.06 μm, with ultrasonic cleaning and plasma argon etching of the substrates before depositing were necessary for sufficient adhesion of the coating. For a gas mixture of benzene and argon with 10 sccm and 20 sccm flow rates, respectively, analysis by scanning electron microscopy (SEM) showed a poor adhesion and carbon films delamination. Nevertheless, the best adhesion of hard coatings to the nitrided layers was achieved when the benzene flow rate was reduced to 4 sccm. Scratch tests revealed that they possess excellent resistance strength (10 to 81GPa) and exhibit both low values of coefficient of friction (0.03 to 0.3) and roughness (0.05–0.24 μm).The Improvement in the carbon films adhesion to the nitrided layers is seen from X-rays diffraction as due to an interlayer formed mainly of phases such as Cr 23 C 6, (Fe,Cr) 7C 3, (Fe,Cr) 3C and Cr 3C 2.

Effects of substrate bias on nanotribologyof a-C:H films deposited by ECR-MPCVD

Nanotribological characterization of amorphous hydrogenated carbon (a-C:H) films is performed by scanning probe microscopy. The a-C:H films are produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition. The influence of substrate bias voltage on nanotribological characteristics is investigated. Scanning probe nanotribological tests, including the nano-friction, nano-wear and nano-scratch, are carried out. Large quantitative variations in friction coefficient and wear depth are found for different substrate biases. Results indicate that higher bias is beneficial to wear and deposition rate, and produces a larger friction coefficient. It also shows that substrate bias plays an important role in the tribological characteristics of a-C:H films.

Electron Cyclotron Resonance Plasma-assisted Reactive Pulsed Laser Deposition of Compound Films

A novel method was developed for low-temperature preparation of thin films. Pulsed laser ablation was combined with electron cyclotron resonance microwave discharge, constituting a novel hybrid film preparation method called electron cyclotron resonance plasma–assisted reactive pulsed laser deposition. We demonstrated the feasibility of the method by preparing compound films of silicon nitride, silicon dioxide, and aluminum nitride from elemental starting materials. The mechanisms responsible for efficient compound formation and film growth are discussed, together with characterization of the prepared films, analysis of the plasma composition, and comparison of the films prepared with and without assistance of the plasma. The unique features of the method make it suitable for one-step preparation of compound thin films at low temperatures.

Combined magnetron sputtering and ECR-CVD deposition of diamond-like carbon films

A novel hybrid technique for diamond-like carbon (DLC) film deposition has been developed, which combines the electron cyclotron resonance microwave plasma discharge of C 2H 2 and metallic magnetron sputtering. In this paper we report our study of this method. The effects of negative bias voltage and hydrocarbon flow rate for the deposition of a-C:H films on high-speed steel were examined by Raman spectra and their hardness was investigated by the Rockwell method. The Raman spectra show that at different hydrocarbon flow rates, the variation of the G line peak and width, and the integrated intensity ratio I D/ I G of DLC and graphic, correlate well with the film hardness. Consequently, we suggest a deposition mechanism of DLC for this combined method.

Electrochemistry of Nitrogen-Incorporated Hydrogenated Amorphous Carbon Films

Nitrogen-doped hydrogenated amorphous carbon, films, were synthesized by microwave electron cyclotron resonance plasma-enhanced chemical vapor deposition, using as precursors. Such films, with thickness in the range of a few tens of nanometers, very smooth, and pinhole free, appear as electrode materials with reactivity and effective window potential similar to those of boron-doped polycrystalline diamond or nitrogen-doped amorphous diamond. These films, grown on Si or Ti substrates, were investigated with regard to their electrochemical reactivity toward outer sphere redox reactions, such as ferri/ferrocyanide, by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). It has been established that the electrical conductivity and the electrochemical reactivity vary in opposite directions, the optimum found for the former being around a nitrogen atomic fraction of 0.3, and for the latter around 0.05. EIS showed that for a fast redox reaction, the behavior, though looking similar to a simple electron transfer on a metallic substrate with a partial diffusion control, has another contribution, which could be explained by the presence of a layer at the interface with the solution, in which electron transport would occur by hopping between many localized states. Ti substrate improves the electrical contact with the carbon film with respect to the Si substrate, which decreases the apparent potential difference between the anodic and cathodic redox peaks by about 150 mV. The minimum value of found for the charge-transfer rate constant of lies in the range so far obtained for other modified carbon materials, such as boron-doped polycrystalline diamond or nitrogen-doped amorphous diamond thin films. © 2002 The Electrochemical Society. All rights reserved.

Influences of substrate bias on the composition and structure of carbon nitride thin films prepared by ECR-plasma assisted pulsed laser deposition

The influences of substrate bias on the properties of carbon nitride thin films, prepared by plasma assisted pulsed laser deposition, are reported. We demonstrated the feasibility of preparation of carbon nitride thin films containing high nitrogen content. A reactive nitrogen plasma was provided by electron cyclotron resonance (ECR) microwave discharge in nitrogen gas. Target ablation and film preparation were performed in the nitrogen plasma environment, with the growing films being concurrently bombarded by the low-energy nitrogen plasma stream. Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy were used for composition determination and structure analysis. Films consisting homogeneously of carbon and nitrogen were obtained on Si (1 0 0) substrates at low temperatures (<80 °C), with nitrogen content over 50 at.% depending on the bias voltage applied to the substrates. Structural analysis reveals that nitrogen and carbon in the films are bonded through hybridized sp 2 and sp 3 configurations and the prepared films can be considered as a compound containing amorphous carbon phase, N-bonded sp 2 and sp 3 hybridized carbon. Besides the composition dependence on the substrate bias voltage, strong influences of the bias voltage on deposition rate and bonding configuration was also observed. The large amount of highly activated nitrogen species created by ECR discharge is expected to be responsible for efficient nitrogen incorporation, bonding formation and film growth. The subsequent surface reactions promoted by the energetic active nitrogen plasma stream enhance the growth of carbon nitride films, while excessive bombardment of the growing film by the plasma stream with higher energies was observed to decrease nitrogen content and deposition rate due to re-sputtering effect.

Electron cyclotron resonance plasma-assisted pulsed laser deposition of boron carbon nitride films

Boron carbon nitride thin films have been prepared on Si (100) substrates by means of plasma-assisted pulsed laser deposition at low temperatures (<80 °C). In this method, a sintered boron carbide (B 4C) target was ablated by laser pulses in the environment of a nitrogen plasma, generated from electron cyclotron resonance (ECR) microwave discharge in pure nitrogen gas, while the growing film was simultaneously being bombarded by the plasma stream. The prepared films are composed of boron, carbon and nitrogen with an average atomic B/C/N ratio of 3:1:3.8 as revealed by X-ray photoelectron spectroscopy (XPS) analysis. XPS, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used for structural characterization. The results suggested that the prepared BCN films contain several chemical bonds with BCN atomic hybridization rather than a simple mixture of BN, BC and CN phases. The BCN films were also found to show good adhesion to the substrates and have a high transparency in the near-infrared region. For comparison, we have also grown BC films in vacuum without plasma assistance. We have found that the assistance of the ECR nitrogen plasma facilitated nitrogen incorporation and film formation.

Characteristics of plasmas in a compact ion source using high-frequency microwave electron cyclotron resonance

A compact electron cyclotron resonance (ECR) ion source (compact ECRIS) for the mass spectrometer was tested. A feature of the compact ECRIS is its size, i.e., inner diameter: 22.5 mm (1 in. tube), length: 56 mm. ECR plasmas in this ion source using argon gas were discharged by high-frequency microwaves, 7–10 GHz. It was confirmed that the plasma was generated in the pressure range 30–410 mPa at the low input power of 5 W.

Growth of Oriented Gallium Nitride Films on Amorphous Substrates by Self Assembly

ABSTRACTC-plane oriented thin films of gallium nitride (GaN) were grown on both amorphous quartz substrates and single crystalline c-sapphire substrates at sub-atmospheric pressures by exposing molten gallium thin films to electron cyclotron resonance (ECR) microwave generated nitrogen plasma. Gallium nitride crystals nucleated from molten gallium and self-aligned with respect to each other due to the mobility of nitrogenated gallium and formed textured film directly on amorphous substrates. Scanning electron microscopy (SEM) images and X-ray Diffraction (XRD) spectra confirmed the orientation among crystals. Micro-Raman spectra exhibited a FWHM of 3 cm−1. Self-assembled, nanocrystalline GaN thin films were obtained when spin-coated gallium thin films (&lt; 1 μm) on quartz substrates were nitrided.

Plasma treatment of polycarbonate for improved adhesion

The deposition of silicon alloys for protective and optical coatings on polymers is of increasing interest. The understanding of the plasma polymer interaction is of prime importance here. In this work, we report a study of the influence of N2, H2, and O2 plasma treatments on pure and commercial grade polycarbonate (PC) in order to enhance the adhesion of plasma deposited silica films. Treatments and depositions were carried out in a low pressure (1 mTorr range) integrated distributed 2.45 GHz microwave electron cyclotron resonance reactor, which allows the deposition of dense stoechiometric silica at room temperature. The plasma–polymer interaction is studied by in situ UV-visible spectroscopic ellipsometry on thin spin-coated PC films. The absorption in the PC layer was found to increase in the UV which was attributed to the different reaction products of photo-Fries rearrangements, especially for pure PC. Gel permeation chromatography measurements showed that the major influence of plasma treatment on pure polycarbonate is chain scission opposed to crosslinking in the case of commercial grade PC, indicating that additives present in commercial grade PC play a major role in the crosslinking mechanisms. The plasma treatment modifies the top 330 nm/homogeneously and no indication of a high index surface layer (50–200 nm) or gradient was found. This is attributed to the low pressure of the plasma treatment, which makes a redeposition of volatile organic species unlikely.

Characterization and Tribological Properties of Nanostructured Copper/Carbon Composite Films Prepared by Microwave Plasma-Assisted Dual Deposition Processes

ABSTRACTNanocrystalline copper/hydrogenated amorphous carbon films have been deposited on Si substrates at the floating potential using a distributed electron cyclotron resonance microwave plasma reactor. In this deposition technique, the microwave plasma-enhanced chemical vapor deposition process of carbon from argon-methane or argon-acetylene mixtures of various compositions was associated with the sputter deposition of copper from a copper target. The total pressure was fixed at 0.13 Pa. For deposition, the substrates mounted on a water-cooled substrate holder were maintained at ambient temperature. The composition of films determined by Rutherford backscattering spectroscopy, energy recoil detection analyses and nuclear reaction analyses was investigated as a function of the gas phase composition. The structure of films was identified by X-ray diffraction (XRD) techniques and the size of copper crystallites incorporated in the amorphous carbon matrix was deduced from XRD data. The magnitude of residual stresses developed in these films was calculated from the radius of curvature of film/substrate samples determined by profilometry. The residual stress values were found to be nearly independent on the composition of films and deposition parameters.

Microstructure and Stress Analyses of Copper Films Deposited on Biased Substrates by Microwave Plasma-Assisted Sputtering

ABSTRACTPure copper films have been deposited on &lt;100&gt; Si substrates either at the floating potential or biased to various dc voltages ranging from 0 to - 125 V. Argon ions from the discharge produced in a distributed electron cyclotron resonance microwave plasma reactor were used for sputtering of a copper target biased to various dc voltages. For sputter deposition, the Si substrates placed on a water-cooled substrate holder were maintained at ambient temperature. The argon pressure was 0.13 Pa and the dc target voltage was fixed at - 600 V. The deposition rate of films was investigated as a function of the substrate bias voltage. The crystallographic structure of films and size of copper crystallites were determined by x-ray diffraction analyses. The surface morphology of films was examined by atomic force microscopy. The electrical resistivity of films was deduced from the thickness and sheet resistance of films determined by profilometry and four point probe measurements, respectively. The magnitude of residual stresses in copper films was calculated from the radius of curvature of Cu/Si samples deduced from profilometry measurements. The evolution of the microstructure, surface morphology and electrical resistivity of films as well as the magnitude of residual stresses developed in these films were studied as functions of the substrate bias voltage. These major characteristics of films were found to be dependent on the energy of argon ions impinging on the surface of films grown on biased substrates. The effect of the ion energy on the physical features of films is analyzed and discussed in this paper.