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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Issue 3 • Date May 2005

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Displaying Results 1 - 25 of 37
  • Issue Cover

    Page(s): c1
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    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Batch process for atomic layer deposition of hafnium silicate thin films on 300-mm-diameter silicon substrates

    Page(s): L1 - L3
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    Atomic layer deposition (ALD) of hafnium silicate HfxSi1-xO2 thin films from tetrakis(ethylmethylamino)hafnium, tetrakis(ethylmethylamino)silicon, and ozone was accomplished onto 300-mm-diam Si substrates using a hot-wall furnace system with a 50-wafer batch configuration. For 23-nm-thick hafnium silicate, excellent film thickness uniformity with a mean within-wafer uniformity of 0.84% (1σ/mean) and a wafer-to-wafer thickness uniformity of 0.80% (1σ/mean) was achieved over the top, middle, and bottom wafers in the full batch process. Over three times enhancement in wafer-per-hour throughput per chamber was observed as compared with a single-wafer ALD module. View full abstract»

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  • Comprehensive analysis of chlorine-containing capacitively coupled plasmas

    Page(s): 369 - 387
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    Capacitively coupled discharges of strongly reactive atmospheres containing mixtures of boron trichloride (BCl3) and chlorine (Cl2) are investigated employing spatially resolved Langmuir probe measurements, and three probes that are spatially integrating methods: optical emission spectroscopy (OES), self-excited electron resonance spectroscopy (SEERS), and impedance characteristics of the discharge. The analysis covers the pure gases including some mixtures, discharge pressure, and rf power over nearly two orders of magnitude, and their impact on important plasma parameters of “first order,” such as plasma density, plasma potential, electron temperature, temperature of the plasma bulk, electron collision rate with neutrals, and actual rf power coupled into the discharge. From these, other properties (electrical conductivity, capacitance, plasma bulk resistance, sheath resistance, and its electrically defined thickness) can be derived. Since the methods are partially complementary, a mutual control of the obtained data is made possible, and we finally obtain a self-consistent model for capacitive coupling connecting data obtained with electrical and optical probes. Compared to electropositive discharges of inert atomic gases (Ar) and molecular gases (H2), which are used as calibration standard for BCl3 and Cl2, the electron plasma density ne is definitely lower, whereas the electron temperature Te is significantly higher, which would be expected by electron attachment to the electronegative molecules—at least at higher discharge pressures. Furthermore, we compared values for Te and ne<- - /formula> obtained with OES and SEERS, respectively, and with the Langmuir-probe system. The agreement in electron plasma density and electron temperature for Ar is surprisingly good, despite the fact that the electron energy distribution would be described with two temperatures. For argon plasma, the variation of the calculated dc conductivity for nearly pure capacitive coupling either from impedance measurements or SEERS is within 30%. This is a result of uncertainties in current path rather than principal faults of the various methods. For the reactive, molecular gases, however, the results vary significantly. These data serve to determine several derived properties. Among these, are the sheath thickness, which is compared with optical and electrical data, and the conductivity of the plasma bulk. As they are derived from simultaneous, but independent measurements, they confirm the relative simple model of an electropositive discharge (argon and argon/krypton), and stress the difficulty to describe plasmas consisting of electronegative constituents (Cl2, BCl3, and their mixtures) which is due mainly to a pressure-dependent transition from stochastic to ohmic heating and from electropositive to electronegative behavior. View full abstract»

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  • Removal of particles during plasma processes using a collector based on the properties of particles suspended in the plasma

    Page(s): 388 - 393
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    A particle removal system based on the properties of charged particles suspended in a plasma for use in controlling particle contamination during the preparation of silicon dioxide thin films in a plasma-enhanced chemical vapor deposition reactor is described. Since the particles suspended in the plasma carry a negative charge, the application of a positive bias to a metal tube inserted into the plasma would attract negatively charged particles. The system effectively removes particles from the trap regions during operation of the plasma. Even particles as small as about 10 nm in size can be removed using this method. Films prepared using the installed particle removal system were found to be nearly free from particle contamination. This is different from the case when the particle removal system is not installed, where some particles are deposited on the film. Even though the particle removal system reduces the rate of film growth by about 40%, it is offset by theresulting clean film, which is free from particle contamination. View full abstract»

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  • Low temperature, fast deposition of metallic titanium nitride films using plasma activated reactive evaporation

    Page(s): 394 - 400
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    Titanium and titanium nitride thin films were deposited on silica glass and W substrates at a high coating growth rate by plasma-activated reactive evaporation (ARE). The crystal structure, preferred orientation and grain size of the coatings were determined by x-ray diffraction (XRD) technique using Cu-Kα x rays. The analysis of the coating morphology was performed by field-emission scanning electron microscopy (FE-SEM). The composition of the films was analyzed by Auger electron spectroscopy (AES) and electron-probe microanalysis (EPMA). The titanium and titanium nitride condensates were collected on a carbon-coated collodion film then characterized by transmission electron microscopy (TEM) in order to study the structures of the deposits at very short deposition times. The resistivity of the films was measured by using the four-point-probe method. The titanium coatings were found to consist of very fine particles (40 nm in grain size) and to exhibit a strong (002) texture. The titanium nitride coatings were substoichiometric (TiNx,x≪1), with an oxygen content ranging from 7 to 15 at. % depending on the deposition conditions. The deposits were found to exhibit a (111) preferred orientation. This behavior became stronger with coating thickness. In spite of the presence of oxygen, all the TiNx coatings obtained at low temperature and a high growth rate in this work exhibited a rather high electrical conductivity. View full abstract»

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  • Amorphous transparent conductive oxide films of In2O3-ZnO with additional Al2O3 impurities

    Page(s): 401 - 407
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    Al-doped In2O3-ZnO films were developed and the influence of Al doping in electrical and optical properties of In2O3-ZnO films was investigated. Amorphous and homologous phases appeared with increasing δ=Zn/(Zn+In) ratios. The carrier generation mechanism is discussed for these films. Native oxygen defects are the primary donors for the In2O3-ZnO films. Then the low resistivities of 2–4×10-4 Ω cm were attained within a narrow range of δ=Zn/(Zn+In) in the amorphous phase film. Two wt % (percent by weight) Al2O3-doping decreased the resistivity to 1.5–2.1×10-4 Ω cm. At doping of 3 and 4 wt % Al2O3, film resistivities of 2–4×10-4 Ω cm were attained for a relatively wide range of δ in the amorphous phase due to an increase in carrier concentration at δ=0.3–0.6. However, Al2O3 doping in homologous phase In2O3-ZnO films decreased carrier concentration independently of the levels of Al2O3 doping. Al2O3 doped in the homologous ZnkIn2Ok+3 crystalline films did not act as a donor impurity. The optical band-gap energy for the films deposited above 2 wt% Al2O3 for amorphous film was proportional to Al2O3 content. This is ascribed to lattice distortion caused by Al2O3. View full abstract»

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  • Role of C2F4, CF2, and ions in C4F8/Ar plasma discharges under active oxide etch conditions in an inductively coupled GEC cell reactor

    Page(s): 408 - 416
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    Utilizing infrared diode-laser absorption spectroscopy (IRDLAS) and UV-Visible absorption spectroscopy (UV-Vis), we show that it is possible to make a near complete mass balance of etch reactants and products in a GEC inductively coupled fluorocarbon discharge while actively etching SiO2 substrates. Langmuir probe measurements were performed to measure the total ion current density. C2F4 and CF2 are shown to be the main dissociation products in a C4F8 plasma discharge. The C2F4 concentration decreases as the SiO2 etching rate increases, along with CF2 and CF radicals, suggesting a role in the SiO2 etching process. The addition of Ar to the C4F8 discharge increased the ion flux at the wafer surface, and the consumption rate of C2F4 relative to CF2. The increased ion flux enhanced the SiO2 etching rate, until at a very high degree of Ar dilution of C4F8/Ar the etching rate became neutral limited. We also monitored SiF2 using UV-Vis absorption and CO by IRDLAS. In our work we found SiF2 and CO to be the prevalent Si and C gas phase etch products for the SiO2 etching process. View full abstract»

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  • Development of low temperature silicon oxide thin films by photo-CVD for surface passivation

    Page(s): 417 - 422
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    Low temperature (250 °C) silicon oxide (a-SiOx:H) films have been developed for surface passivation as well as antireflection coating in silicon solar cell. Films have been fabricated by ion damage free photochemical vapor decomposition technique using SiH4, N2O, and H2 gas mixture. In this paper we have reported the effect of N2O to SiH4 ratio (R) on optoelectronic and structural properties of the films. The bonding configurations of Si and H were investigated in detail by IR absorption measurement. The SiH stretching mode supports the presence of H–(Si3-nOn)(n=0–3) structural unit, which is also present in the SiO stretching mode. Developed silicon oxide films also have been studied on the c-Si solar cell. A substantial enhancement (11.2%) in efficiency has been achieved. View full abstract»

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  • Investigation of the nanostructure and wear properties of physical vapor deposited CrCuN nanocomposite coatings

    Page(s): 423 - 433
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    This article presents results on CrCuN nanocomposite coatings grown by physical vapor deposition. The immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of depositing a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or β-Cr2N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. Hardness, wear resistance, and impact resistance have been determined by nanoindentation, reciprocating-sliding, and ball-on-plate high-cycle impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprised of 1–3 nm α-Cr(N) and β-Cr2N grains separated by intergranular regions of Cu gives rise to a coating with significantly enhanced resistance to impact wear. View full abstract»

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  • Wettability and thermal stability of fluorocarbon films deposited by deep reactive ion etching

    Page(s): 434 - 439
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    Fluorocarbon films have low surface energy and can be used as antistiction coating for microelectromechanical systems. By using the passivation process in a deep reactive ion etcher, the fluorocarbon films can be deposited and integrated with other processes in the clean room. The properties such as wettability, surface energies, and thermal stability, have been investigated in detail. It has been found that the fluorocarbon films deposited have a static water contact angle of 109° and a surface energy around 14.5 mJ/m2, whereas as-received and as-deposited single silicon, poly silicon, and silicon nitride have a much lower water contact angle and a higher surface energy. The fluorocarbon films keep their good hydrophobicity up to 300 °C, and the degradation temperature depends on the thickness of the fluorocarbon films. Decomposition happens at lower temperatures (100–300 °C) even though the decomposition rate is quite slow without affecting the contact angle. The decomposition mechanism at low temperatures (less than 300 °C) might be different from that at high temperatures. It has been shown that the fluorocarbon film deposited by a deep reactive ion etcher tool provides very high hydrophobicity, low surface energy, good thermal stability, and antiadhesion behavior for use in nanoimprinting lithography. View full abstract»

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  • Discharge mode transitions in low-frequency inductively coupled plasmas with internal oscillating current sheets

    Page(s): 440 - 447
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    Transitions between the two discharge modes in a low-frequency (∼460 kHz) inductively coupled plasma sustained by an internal oscillating radio frequency (rf) current sheet are studied. The unidirectional rf current sheet is generated by an internal antenna comprising two orthogonal sets of synphased rf currents driven in alternately reconnected copper litz wires. It is shown that in the low-to-intermediate pressure range the plasma source can be operated in the electrostatic (E) and electromagnetic (H) discharge modes. The brightness of the E-mode argon plasma glow is found remarkably higher than in inductively coupled plasmas with external flat spiral “pancake” coils. The cyclic variations of the input rf power result in pronounced hysteretic variations of the optical emission intensity and main circuit parameters of the plasma source. Under certain conditions, it appears possible to achieve a spontaneous E→H transition (“self-transition”). The observed phenomenon can be attributed to the thermal drift of the plasma parameters due to the overheating of the working gas. The discharge destabilizing factors due to the gas heating and step-wise ionization are also discussed. View full abstract»

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  • Characterization of epitaxial germanium grown on (LaxY1-x)2O3/Si(111) using different surfactants

    Page(s): 448 - 451
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    The uniformity and quality of epitaxial, ultrathin germanium-on-insulator (GOI) layers are studied as a function of Ge regrowth under different surfactant conditions. It is shown that using antimony as a surfactant during the solid phase epitaxial regrowth of the germanium layers provides a higher crystal quality and much flatter surfaces than samples grown without antimony. However, the diffusion of even a small percentage of a monolayer of antimony into the GOI layer may cause a thin n+ “delta-doped” layer to remain on the surface of the wafer, making device fabrication difficult. It is shown that using a surface layer of silicon as a surfactant that is not expected to interact electronically with the Ge (unlike Sb), acceptable surface smoothness may be achieved. Physical mechanisms behind this are discussed. View full abstract»

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  • Effect of O2 flow ratio on the microstructure and stress of room temperature reactively sputtered RuOx thin films

    Page(s): 452 - 459
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    RuOx thin films were deposited at room temperature by reactive radio frequency magnetron-sputtering using Ar/O2 discharges of varying O2 flow ratio (fO2) over the range 10%–50% and were characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, resistivity, and stress-temperature measurements. With the increase of fO2, the film texture changed from (110) to (101). Films deposited with fO2≫25% were determined stoichiometric. The residual stresses in as-deposited films were all compressive and increased with addition of O2, except for the film sputtered at fO2=20% which was in biaxial tension. The film deposited at fO2=30% had a low resistivity value of 68 μΩ cm and near zero stress (≪50 MPa tensile) after a thermal cycle in air up to 500 °C which is promising for use in microdevices. View full abstract»

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  • Using beam flux monitor as Langmuir probe for plasma-assisted molecular beam epitaxy

    Page(s): 460 - 464
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    We present a simple method for measuring the ion flux from a molecular beam epitaxy (MBE) plasma cell in real time. A Langmuir probe was created by attaching the beam flux monitor to a picoammeter and measuring the current impinging upon the collector or filament wires. This provides a noninvasive, convenient, and direct measure of ion flux at the actual wafer position, yet requires no internal changes to the MBE machine. Quantitative measurements of maximum ion energies and relative ion fluxes are possible. Real-time feedback from this measurement allows rapid optimization of the plasma for the minimum ion flux. This method is applicable to GaN and related materials, but is particularly important for growth of dilute nitrides. This was one of the techniques which led to the longest wavelength GaInNAs(Sb) vertical cavity surface emitting lasers and continuous wave edge emitting lasers on GaAs to date. View full abstract»

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  • Enhancement of mechanical properties of organosilicon thin films deposited from diethylsilane

    Page(s): 465 - 469
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    A strong demand exists for improved low-k intermetal dielectric materials, such as organosilicons, to enhance the performance of ultralarge scale integrated circuits. Pulsed-plasma enhanced chemical vapor deposition was used to deposit organosilicon thin films from diethylsilane and oxygen. Fourier-transform infrared (FTIR) analysis showed significant organic content as well as hydroxyl and silanol moieties in the as-deposited materials. FTIR showed a complete removal of hydroxyl groups after annealing at 400 °C for 1 h. This removal indicates a condensation reaction between proximal hydroxyl groups leading to the formation of additional SiOSi linkages, which would increase both the hardness and modulus of the film. Mechanical property measurements were in accordance with this hypothesis, as both the hardness and modulus increased by over 50% after annealing. Film structure and properties were strongly dependent on the precursor feed ratio. View full abstract»

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  • Adsorbate effects on pulsed electron diode anode thermal response

    Page(s): 470 - 474
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    Anode thermal response is important in determining the operation of repetitively pulsed electron diodes and the systems using them. Thermal response determines desorption, cooling requirements, and power deposition. This article describes experimental results from an electron beam diode fitted with both solid aluminum and two types of carbon-carbon fiber anodes. The temperature response is modeled and is used in conjunction with experimental data to study the effect of adsorbates on the anode. Power to the anode is determined through the material properties and modeled temperature response. Thermal properties of the anode are considered with respect to electron stimulated desorption of adsorbates on the anode as an ion source, leading to plasma development and diode impedance collapse. View full abstract»

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  • Electron impact effects on the oxidation of Si(111) at 90 K

    Page(s): 475 - 479
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    The Si(111)-7×7 surface has been subjected to oxidation by molecular O2 at 90 K and the kinetics of this process have been studied by x-ray photoelectron spectroscopy (XPS). In the midst of the oxidation process, the thin oxide layer was electronically excited in ultrahigh vacuum using 100 eV electron bombardment. No charging of the oxide layer was observed. It was found that excitation of the oxide layer by electron bombardment led to almost no change in the oxidation kinetics, measured following bombardment. XPS studies showed that two oxygen-containing surface species are produced by oxidation (in the absence of electrons) with O(1s) binding energies of 533.1 and 535.1 eV. Upon electron bombardment, the higher binding energy species is converted to the lower binding energy species. Continued oxidation after electron bombardment showed that the higher binding energy species was replenished again. This result suggests that adsorption at 90 K leads to highly strained Si–O–Si species and that electron bombardment of these species produces the stable oxidized structure. The results are compared to similar experiments on Al2O3 where, in contrast to a SiO2 film, it was found that surface charging of a thin Al2O3 film on Al(111) leads to a greatly enhanced oxidation rate. View full abstract»

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  • Effect of ion entry acceptance conditions on the performance of a quadrupole mass spectrometer operated in upper and lower stability regions

    Page(s): 480 - 487
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    Computer simulation of ion motion in a quadrupole mass spectrometer has been used to examine the effect of initial ion conditions on performance when operated in the first and third zones of the Mathieu stability diagram. Commercial instruments frequently use round electrodes instead of the better-performing hyperbolic electrodes because the cost of manufacturing is lower. However, adverse features are seen when using round electrodes. Here further insight is provided and a possible method of correction is suggested. For the first time, ion origin for the first stability region for a round electrode quadrupole has been reported. View full abstract»

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  • Plasma enhanced atomic layer deposition of HfO2 and ZrO2 high-k thin films

    Page(s): 488 - 496
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    A plasma enhanced atomic layer deposition (PEALD) process was developed to deposit high-k dielectric constant materials using alternative metal t-butoxide and oxygen plasma exposures. The deposited thickness increased linearly with an increasing number of precursor/oxygen plasma cycles, and the growth rates of HfO2 and ZrO2 were determined to be 1.1 and 2.8 Å/cycle, respectively. The as-deposited films were determined to be fully oxidized and amorphous by the x-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). The PEALD films were found to have high concentrations of bridging oxygen bonds with metals (M–O–M) as the film thickness increased, in contrast to the high concentrations of M–O–H in the films deposited by plasma enhanced chemical vapor deposition (PECVD). The M–O–M bonds in the PEALD films were further increased upon annealing at 250 °C in atmosphere with a corresponding decrease in M–O–H concentrations, suggesting the elimination of hydroxyl groups upon annealing. The PEALD HfO2 and ZrO2 films showed higher dielectric constants (25, 22) than those of PECVD deposited films (21, 19), likely due to the enhanced ionic contribution from the M–O–M bonds in the PEALD films. The smallest equivalent oxide thickness (EOT) of 13 Å was achieved by PEALD HfO2 with a leakage current density of 0.2 A/cm2, several orders of magnitude below that of thermally grown SiO2 films with the same EOT. View full abstract»

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  • X-ray photoelectron spectroscopic observation on B–C–N hybrids synthesized by ion beam deposition of borazine

    Page(s): 497 - 502
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    B–C–N hybrid thin films were grown from ion beam plasma of borazine (B3N3H6) on graphite substrate at room temperature, 600 °C, and 850 °C. The films were characterized in situ by x-ray photoelectron spectroscopy (XPS). XPS study suggested that B and N atoms in the deposited films are in a wide variety of chemical bonds, e.g., B–C, B–N, N–C, and B–C–N. The substrate temperature and ion fluence were shown to have a significant effect on the coordination and elemental binding states on the B–C–N hybrids. It was found that B–C–N hybrid formation is enhanced at high temperature, and this component is dominantly synthesized at low fluence. The results imply that it is possible to control the composition of B–C–N hybrid by changing the ion fluence and the temperature during ion implantation. View full abstract»

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  • Temperature dependence of resistivity of Si–Ta film deposited by magnetron sputtering

    Page(s): 503 - 505
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    Analysis of conductivity of silicon films doped with tantalum, based on percolation theory, has been carried out. The dependence of resistivity on Ta content in the film and temperature has been presented. The films were deposited by magnetron sputtering on glass substrates. The films with the thickness of ∼0.3 μm contained from 2% to 20% of Ta. Based on percolation theory, the effect of Ta content on resistivity and its dependence on temperature were determined. View full abstract»

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  • Anti-emission characteristics of the grid coated with hafnium film

    Page(s): 506 - 511
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    Hf was deposited onto the surface of Mo grids by ion-beam-assisted deposition. The electron-emission characteristics of the grids with and without Hf, which were contaminated by active electron-emission substances (Ba, BaO) of the cathode, were measured using an analogous-diode method. The surfaces of the grids were analyzed by x-ray diffraction and x-ray photoelectron spectroscopy. The results showed that electron-emission current from the Mo grid coated with Hf film was less than that from the Mo grid without Hf. During the course of the testing, active electron-emission substances from the cathode were deposited continuously onto the surface of the grid. Due to BaHfO3 compounds and Ba-Hf diffusion, the Mo grid coated with Hf effectively reduced the electron-emission substances on the grid from the cathode, which reduced grid electron emission. View full abstract»

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  • Effects of substrate temperature on properties of pulsed dc reactively sputtered tantalum oxide films

    Page(s): 512 - 519
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    The effects of substrate heating on the stoichiometry and the electrical properties of pulsed dc reactively sputtered tantalum oxide films over a range of film thickness (0.14 to 5.4 μm) are discussed. The film stoichiometry, and hence the electrical properties, of tantalum oxide films; e.g., breakdown field, leakage current density, dielectric constant, and dielectric loss are compared for two different cases: (a) when no intentional substrate/film cooling is provided, and (b) when the substrate is water cooled during deposition. All other operating conditions are the same, and the film thickness is directly related to deposition time. The tantalum oxide films deposited on the water-cooled substrates are stoichiometric, and exhibit excellent electrical properties over the entire range of film thickness. “Noncooled” tantalum oxide films are stoichiometric up to ∼1 μm film thickness, beyond that the deposited oxide is increasingly nonstoichiometric. The presence of partially oxidized Ta in thicker (≫∼1 μm) noncooled tantalum oxide films causes a lower breakdown field, higher leakage current density, higher apparent dielectric constant, and dielectric loss. The growth of nonstoichiometric tantalum oxide in thicker noncooled films is attributed to decreased surface oxygen concentration due to oxygen recombination and desorption at higher film temperatures (≫∼100 °C). The quantitative results presented reflect experience with a specific piece of equipment; however, the procedures presented can be used to characterize deposition processes in which film stoichiometry can change. View full abstract»

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  • Etching of oxynitride thin films using inductively coupled plasma

    Page(s): 520 - 524
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    In this study, silicon oxynitride (SiON) has been etched in a C2F6 inductively coupled plasma. The process parameters examined include a radio frequency source power, bias power, pressure, and C2F6 flow rate. For process optimization, a statistical experimental design was employed to investigate parameter effects under various plasma conditions. The etch rate increased almost linearly with increasing the source or bias power. Main effect analysis revealed that the etch rate is dominated by the source power. The C2F6 flow rate exerted the least impact on both etch rate and profile angle. It was estimated that the C2F6 effect is transparent only as the etchant is supplied sufficiently. Depending on the pressure levels, the etch rate varied in a complicated way. Parameter effects on the profile angle were very small and the profile angle varied between 83° and 87° for all etching experiments. In nearly all experiments, microtrenching was observed. The etch rate and profile angle, optimized at 1000 W source power, 30 W bias power, 6 mTorr pressure, and 60 sccm C2F6 flow rate, are 434 nm/min and 86°, respectively. View full abstract»

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Aims & Scope

The Journal of Vacuum Science and Technology A is devoted to reports of original research, review articles, and Critical Review articles.

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G. Lucovsky
North Carolina State University