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

Issue 6 • Date Nov 1996

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  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Current capabilities and limitations of in situ particle monitors in silicon processing equipment

    Page(s): 2983 - 2993
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    By enabling real time monitoring and control of particle levels in integrated circuit process equipment, in situ particle monitors (ISPMs) have the potential to reduce dramatically the dominant source of yield‐killing defects, i.e., process induced particles. However, there are also significant limitations to their use for on‐line monitoring. A survey of the ISPM literature shows that the greatest benefit provided by ISPMs for most applications is their immediate indication of high‐particle excursions. In only a few applications described in the literature do the sensor data correlate with wafer surface scans and show enough sensitivity to baseline particle levels to control process maintenance cycles. Scaling arguments show that at gas pressures below about 100 mTorr, gravitational settling and particle inertia typically prevent particles from being carried efficiently to exhaust sensors, in spite of experimental evidence that bouncing significantly aids particle transport. Combined with the low sampling efficiency of most sensors, these limitations make exhaust sensors impractical for many applications including most sputtering and many etching processes, unless chambers are regularly vented to high pressures. The cutoff imposed by particle transport limitations is clearly demarcated in the ISPM literature, which indicates good sensitivity of exhaust sensors to baseline particle levels in high pressure processes such as plasma‐enhanced chemical‐vapor deposition, sensitivity only to high‐particle excursions for processes around 100 mTorr, and insensitivity to particle levels in processes that operate at low pressures, except during gas venting or purging. For many applications, standard sensors are susceptible to false counting due to fouled optics, noise from rf and magnetic fields, and optical emissions. High current ion implanters, with their nearly noise‐free chambers, are the only fully proven application- - of in‐chamber sensors. To overcome the particle transport limitations in other critical defect‐producing processes that operate at low pressure, in‐chamber sensors that are insensitive to the harsh chemistry and high noise levels of process chambers need to be developed. © 1996 American Vacuum Society View full abstract»

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  • Reactive ion etching of silica structures for integrated optics applications

    Page(s): 2994 - 3003
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    Reactive ion etching of silica in a hollow cathode reactor using a CHF3/Ar gas mixture has been studied as a function of masking material, rf power, sample temperature, and O2 and CF4 additions. Etch rates in excess of 0.5 μm/min are typically obtained with a selectivity over amorphous silicon and photoresist of more than 10. The sidewall roughness for etching with an amorphous silicon mask is of the order of 0.05 μm, whereas for a photoresist mask, under similar etching conditions, the sidewall roughness is up to 0.1 μm. For the a‐Si mask a further improvement in the sidewall roughness down to 0.02 μm can be obtained by adding O2 to the discharge or elevating the sample temperature, however both parameters cause lateral etching of the a‐Si mask and therefore linewidth loss. Nonetheless, when using sample temperature as a control parameter, a process window was found which allows smooth sidewalls to be obtained without dimension loss. In the case of O2 additions such a process window was not found. Possible mechanisms accounting for this difference are discussed. Etching in a CHF3/Ar discharge occurs in competition with simultaneous polymer deposition. The polymer deposition rate was measured in areas shielded from ion bombardment. A phenomenological model describing the effects of polymer deposition on etch rates, sidewall slope, and roughness is proposed. This model assumes that a polymer film with different steady‐state thickness can form on different etched structure surfaces, as a result of a balance between polymer etching and deposition. The model is used to explain the tendencies in etch rates, profile slope, and sidewall roughness obtained in this study. © 1996 American Vacuum Society View full abstract»

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  • Effect of supplied substrate bias frequency in ultrahigh‐frequency plasma discharge for precise etching processes

    Page(s): 3004 - 3009
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    The characteristics of silicon etching using radio‐frequency (rf) substrate biased ultrahigh‐frequency (UHF) plasma determined by using a Cl2 etchant were investigated. The silicon etching rate and the etching profile were improved by decreasing the substrate bias frequency to less than 600 kHz. It is suggested that a large number of negative chlorine ions is generated in the high‐density, low‐pressure UHF plasma because of the extremely low electron temperature. The low‐frequency substrate bias accelerates the negative and positive ions alternately to the substrate surface. As a result, the low‐frequency biased UHF plasma can be used to achieve high‐rate, highly anisotropic, and microloading‐free silicon etching with a 600 kHz rf substrate bias. © 1996 American Vacuum Society View full abstract»

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  • Etching characteristics of tin oxide thin films in argon–chlorine radio frequency plasmas

    Page(s): 3010 - 3016
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    We have developed an etch process suitable for high resolution transparent conductive oxide patterning with high etch rates, up to 70 nm/min, and applicability to large area flat panel display substrates. It was found that the addition of small amounts of Cl2 significantly enhanced the etch rate compared to addition of pure argon but that beyond 25% Cl2 the rate tended to fall. There is a significant loading effect where the etch rate approximately doubled for exposed tin oxide areas between 80% and 10% of the substrate area. This loading sensitivity was found to increase with increasing power and decreasing Cl2 concentration. It was also observed that local changes in pattern dimensions affected the uniformity of the etch rate. A large photoresist etch rate was observed between one and three times that of the tin oxide and it decreased as the area of photoresist coverage increased. Linewidth loss, up to 4 μm at high powers, was overcome using improved ultraviolet exposure, leading to feature resolution capabilities of ≪5 μm. Etch rate inhomogeneity was also observed on a local scale, possibly due to redeposition of sputtered photoresist. Overetching, however, ensures rapid clearing of tin oxide islands without damage to the underlying SiO2 buffer layer. © 1996 American Vacuum Society View full abstract»

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  • Integrated processing of silicon oxynitride films by combined plasma and rapid‐thermal processing

    Page(s): 3017 - 3023
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    Silicon oxynitride (OXN) gate dielectric thin films have been prepared in a cluster tool using a low thermal‐budget process combining plasma and rapid‐thermal step. This N2‐based process has (i) increased process latitude for the formation of N‐rich alloys, and (ii) resulted in lower bonded‐H concentrations, in comparison to NH3‐based processes. On‐line Auger electron spectroscopy and off‐line infrared spectroscopy have been used to characterize chemical bonding, showing that the deposited films are pseudobinary alloys, (SiO2)x(Si3N4)1-x. The processing steps are (i) a 300 °C plasma‐assisted oxidation, (ii) a 300 °C plasma‐assisted chemical vapor deposition of oxynitride films, and (iii) a 30 s, 900 °C postdeposition rapid‐thermal anneal. Electrical characterization of O–OXN–O structures in metal–oxide–semiconductor capacitors was performed using capacitance–voltage techniques to evaluate the effect of alloy composition on midgap interface state density, Dit, and flat‐band voltage, Vfb. © 1996 American Vacuum Society View full abstract»

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  • Ion–surface interactions in low temperature silicon epitaxy by remote plasma enhanced chemical–vapor deposition

    Page(s): 3024 - 3032
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    Epitaxial Si thin films have been deposited by remote plasma enhanced chemical–vapor deposition at temperatures below 450 °C and at pressures between 50 and 500 mTorr. Growth rate data reveal the presence of two pressure dependent regimes for deposition process activation. Sampling of the plasma afterglow by mass spectrometry indicates a correlation between enhanced rates for single crystal film formation and the onset of an ion‐induced surface H abstraction processes below pressures of ∼200 mTorr. The role of low energy ions in the abstraction of chemisorbed H and its effects on the growth kinetics are discussed. © 1996 American Vacuum Society View full abstract»

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  • The radio frequency hollow cathode plasma jet arc for the film deposition

    Page(s): 3033 - 3038
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    The radio frequency hollow cathode plasma jet (RPJ or RHCPJ) arc discharge is studied for an activated reactive deposition of TiN films. The presence of low content of nitrogen in argon enables reaching the arc regime at lower powers than in pure argon. The transition into the distributed arc after admission of low content of nitrogen results in an extreme enhancement of TiN deposition rate (20–30× higher than for Ti) and at the same time in an effective incorporation of nitrogen into the film. The spontaneously repeated transitions between the hollow cathode discharge and RHCPJ arc at particular parameters are studied. The time development and the character of these transitions confirm the substantial role of metastable argon atoms in the discharge. The comparison of several cathode materials is presented. The reactive deposition of TiN films at low nitrogen pressure without argon is examined. © 1996 American Vacuum Society View full abstract»

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  • Generation of an electron cyclotron resonance plasma using coaxial‐type open‐ended dielectric cavity with permanent magnets

    Page(s): 3039 - 3042
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    A high density, uniform, and compact electron cyclotron resonance (ECR) plasma source which utilizes surface‐wave radiation and a near‐surface magnetic field is described. The microwaves propagated through a coaxial waveguide are introduced circularly into the circumferential side of a dielectric Al2O3 disk, which is placed at the open end of a coaxial‐type cavity. The ECR magnetic field is similar to three concentric planar magnetron configurations and is directed away from the dielectric surface by permanent magnets set in the center conductor of the coaxial‐type cavity. A surface wave is launched from the dielectric disk surface and generates an ECR plasma. The plasma density and electron temperature are 2.0×1011 cm-3 and 2.2 eV, respectively, at an Ar gas pressure of 10 mTorr and a microwave power of 700 W. The ion saturation current density (Isat) and its uniformity are 8.2 mA/cm2 and ±5.5% within a radius of 10 cm. © 1996 American Vacuum Society View full abstract»

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  • ‘‘Self‐thickness‐limited’’ plasma polymerization of an ultrathin antiadhesive film

    Page(s): 3043 - 3048
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    Ultrathin (≪5 nm) fluorinated polymer films of homogeneous thicknesses have been deposited from a CF4/H2 microwave discharge. The films have an extremely low surface energy of 4.2 mJ/m2, which is more than four times lower than that for polytetrafluoroethylene. The deposition was carried out in a type of ‘‘self‐thickness‐limited’’ mode, in which the thickness of the deposited polymer film is limited by the plasma parameters. The deposition can be separated into two phases, a growth and a treatment phase. During the treatment phase, the deposited film is fluorinated, which results in a dramatic decrease of the surface energy. The thickness limiting behavior of the plasma is explained by the dualism of etching and polymerization occurring in fluorocarbon discharges. The film was tested as antiadhesion film for the replication of micro‐optical structures, using a Ni shim with a very fine surface relief grating (400 nm periodicity) to hot emboss (at 180 °C) polycarbonate sheed. The tests demonstrate the excellent antiadhesive property of the film with the polycarbonate and reveal a good adhesion of the film with the Ni substrate. © 1996 American Vacuum Society View full abstract»

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  • Pulse–time‐modulated electron cyclotron resonance plasma discharge for highly selective, highly anisotropic, and charge‐free etching

    Page(s): 3049 - 3058
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    Highly selective, highly anisotropic, notch‐free, and charge‐buildup damage‐free silicon etching is performed using electron cyclotron resonance (ECR) Cl2 plasma modulated at a pulse timing of a few tens of microseconds. A large quantity of negative ions are produced in the afterglow of the pulse‐time‐modulated plasma. The decay times of electron density, electron temperature, and sheath potential are considerably reduced. This is attributable to negative‐ion generation. Furthermore, the pulse‐time‐modulated plasma reduces the time averaged sheath potential. As a result of these effects, charged particles in the sheath are drastically modified from the continuous discharge, and they should improve the selective etching in the pulsed ECR plasma and eliminate charge accumulation on the substrate. Additionally, negative‐ion generation dramatically improves the plasma potential distributions in the nonuniform ECR plasma. This technique is also suitable for large scaled etching processes. © 1996 American Vacuum Society View full abstract»

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  • Electric field control of plasma and macroparticles in cathodic arc deposition as a practical alternative to magnetic fields in ducts

    Page(s): 3059 - 3064
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    Plasma transportation and ion losses in a cathodic arc fitted with a curved magnetic macroparticle filter are studied for different magnetic field configurations. A planar Langmuir probe was used to carry out ion saturation current measurements along the axis of the duct, so that the losses of ions could be quantified. The losses of ions were found to depend sensitively on the magnetic field configuration in the prefilter region. The potential of the duct wall was measured as a function of distance to the cathode and the results were used to locate the effective anode of the discharge. The location of the effective anode was determined by the magnetic field configuration and affected the running stability of the arc. The conditions which provided the best efficiency of plasma transport also gave the least stable running conditions. The use of an electric field as a macroparticle filter was studied and higher deposition rates for coatings of comparable quality were found to be deposited onto a substrate held parallel to the drift velocity of the plasma to which a negative bias was applied. © 1996 American Vacuum Society View full abstract»

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  • Surface wave operation mode of the slot antenna microwave plasma source SLAN

    Page(s): 3065 - 3070
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    A new slot antenna concept allows the generation of large volume 2.45 GHz discharges. The microwave power is coupled from an annular waveguide (ring cavity) through ten equidistantly positioned resonant coupling slots into the quartz plasma chamber. Langmuir double probe axial distribution measurements of the electron density and temperature are performed for argon, helium and nitrogen discharges in a power range from 120 to 1200 W and a pressure range from 10 to 150 Pa. Characteristic differences in the discharge behavior for the various gases are presented. With argon a surface wave at the plasma‐quartz interface can be excited, already at 200 W. The resulting plasma column can extend up to 450 mm in length along the tube with 160 mm diameter. The surface wave mode is identified as a m=5 mode by visual inspection of the plasma formation and by recording the azimuthal electric field distribution. In contrast to argon, for helium and nitrogen no surface wave generation for power levels up to 1200 W are observed. Within the investigated power range both gases show a diffusion controlled variation of the electron density. This is verified by fitting the axial density data to the time‐independent diffusion equation for helium and nitrogen and to a simplified surface wave model for argon. © 1996 American Vacuum Society View full abstract»

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  • Measurements of spatial and temporal sheath evolution inside tubular material for inner surface ion implantation

    Page(s): 3071 - 3074
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    Tubular target of aluminum (inner radius=5 cm, length=15 cm) was immersed in a nitrogen plasma with plasma densities of 6.8×109–5×1010 cm-3 and biased negatively (10–30 kV). A Langmuir probe was used to detect the propagating sheath edge. A comparison of experiment measurements and numerical calculations of temporal and spatial sheath evolution is presented. Experiment measurements of sheath edge position were in good agreement with those determined by numerical calculations. © 1996 American Vacuum Society View full abstract»

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  • Oxygen plasma asher contamination: An analysis of sources and remedies

    Page(s): 3075 - 3081
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    The low Earth orbit (LEO) environment is commonly simulated using oxygen plasma ashers to determine the effects of LEO on spacecraft materials. However, plasma ashers can also contaminate samples during plasma exposure, making them less than ideal for space simulation. This study results from attempts to minimize or eliminate contamination. Optical methods of variable angle spectroscopic ellipsometry and reflectance spectrophotometry were used to quantify contaminant stoichiometry and deposition rate. Auger electron spectroscopy identified deposited contaminants and their surface coverage. Contamination results from etching of the rubber chamber seals by the plasma. The deposited contaminant was nearly indistinguishable from fully stoichiometric SiO2. Contaminant deposition rates up to 0.27 nm/min have been observed, and these layers effectively passivate the surface by depositing an overcoat of SiOx. Placing metal into the path of the plasma before it can reach the chamber seals greatly reduces contamination. A newly designed chamber confines the plasma to a small volume away from the chamber seals. For fluences as high as 3.5×1022 atoms/cm2, equivalent to 7.5 years of space exposure for the International Space Station, the redesigned asher showed less than one monolayer of deposited contaminant. © 1996 American Vacuum Society View full abstract»

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  • Ashing residues on TiN antireflective coating layers

    Page(s): 3082 - 3086
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    Residues appearing on the surface of the TiN antireflective coating (ARC) layer after a resist ashing process were investigated by transmission electron microscope and field emission Auger electron spectroscopy. These residues tend to appear linearly in the center of Al lines covered with the TiN ARC layer, and are generally called the ‘‘backbone.’’ We found that a triangular product mainly composed of Al atoms appears in the center of the resist surface in the final stage of the ashing process and that a thin layer, about 10 nm thick, including Ti atoms, is formed to cover the triangular product and the resist surface. Due to the small solubility of the thin layer including Ti atoms to the alkaline stripper, the triangular product under the thin layer remains as a backbone residue. We demonstrate that the formation of the backbone depends on the distribution of Al and Ti atoms in the sidewall polymer. © 1996 American Vacuum Society View full abstract»

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  • Sputtering of metallic walls in Ar/H2 direct current glow discharges at room temperature

    Page(s): 3087 - 3091
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    Laser induced fluorescence of Cr atoms in their ground state have been used to characterize metallic sputtering in dc glow discharges (GDs) of hydrogen/argon admixtures in a stainless steel chamber at room temperature. A strong decrease in the sputtering signal was observed upon addition of H2 to the pure Ar GD plasma, at constant pressure and total current conditions, even at low H2 concentrations in the admixture. The plasma microscopic parameters have been determined from actinometry and Langmuir probe data. The H implantation characteristics of the studied plasmas were also determined by pump and release experiments. According to all the experimental evidence, hydrogen implantation in the metal surface is the main process responsible for the observed sputtering suppression. The results are compared to similar sputtering reduction observations previously reported in other light contaminant/metal systems. © 1996 American Vacuum Society View full abstract»

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  • Effect of nonstoichiometry upon optical properties of radio frequency sputtered Al–N thin films formed at various sputtering pressures

    Page(s): 3092 - 3099
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    Colored Al–N films can be easily made through changing the content of nitrogen gas at various sputtering pressures. For films deposited at 5×10-2 Torr, with only slight change in the proportion of nitrogen gas from 0% to 2.5%, 5%, 7.5%, and 10%, the respective visual appearance changed from silver–gray to gray, gray, green–yellow to transparent. With the further increase in the content of nitrogen gas up to 100%, the obtained films were all transparent. For films formed at 5×10-1 Torr, with the content of nitrogen gas being 0%, 2.5%, 5%, 7.5%, 10%, and 20%, the corresponding visual appearance of the films were silver–gray, black, dark‐green–yellow, green–yellow, light‐yellow and transparent. When the content of nitrogen gas changed from 20% to 100%, there was almost no difference in the visual appearance. For films formed at 1 Torr, when the content of nitrogen gas was only over 2.5%, the film became clear. Measurements of transmittance, reflectance, and thickness, calculations of the absorption coefficient, refractive index, and extinction coefficient, and an x‐ray photoemission spectroscopy analysis show that the coloration is mainly due to the nonstoichiometry induced by lower content of nitrogen gas at various sputtering pressures. Furthermore, the calculated extinction coefficients are found to have a much closer relationship with the coloration than other parameters, such as, refractive index and thickness. The optical band gap of the obtained stoichiometric AlN films is 5.85–5.9 eV. © 1996 American Vacuum Society View full abstract»

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  • Low‐temperature deposition of cubic BN:C films by unbalanced direct current magnetron sputtering of a B4C target

    Page(s): 3100 - 3107
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    Controllable‐unbalanced dc magnetron sputtering of a B4C target in mixed Ar–N2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5–21 at. % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film elemental composition. An additional axially symmetric magnetic field was used to vary the discharge plasma density near the substrate in a wide range. Hence, the ion flux Ji of primary Ar+ and N+2 ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux Jn (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion‐to‐neutral flux ratios 3≤Ji/Jn≤24, ion energies Ei≤500 eV, and substrate temperatures 150≤Ts≤350 °C. The phase and elemental composition of as‐deposited BN:C films were characterized by Fourier transform infrared spectroscopy and wavelength dispersive x‐ray spectroscopy, respectively. Deposition of cubic phase c‐BN:C containing 5–7 at. % of C is demonstrated under conditions of low energy (110 eV) ion bombardment, a high ion‐to‐atom arrival rate ratio (Ji/Jn∼24), and low growth temperatures (∼150 °C). © 1996 American Vacuum Society View full abstract»

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  • Monte Carlo numerical analysis of target erosion and film growth in a three‐dimensional sputtering chamber

    Page(s): 3108 - 3123
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    A combination of two mathematical models for three‐dimensional Monte Carlo particle simulation of a low pressure sputtering environment is proposed. One is intended for the simulation of a discharge gas flow, and the other for the sputtered atom transport. The combination is used to characterize target erosion and film growth. The models are refined with recourse to experimental measurements made in a practical sputtering apparatus (SPF‐210 AS, ANELVA Ltd.) over the range of operating pressures and flow rates of 0.3–10 Pa and 0.5–5 sccm, respectively. A considerable number of numerical analyses are done to find possible reasons for the measured nonuniformity of target erosion and film growth rate distributions. Simulation results show that under the operating and design conditions treated here the nonuniformity of gas flow field appears to be too weak to explain the experimental data. Film growth rates simulated for measured erosion rates show a good agreement with the experimental data for the various operating pressures above. Important features of the present simulation are the inclination of the angular distribution of sputtered atoms, and taking into consideration reemission of sputtered atoms deposited onto the target. The inclination of angular distribution results from the oblique ion incidence onto the target surface. The existence of highly eroded etch track along the target edge is shown to be correlated with the greater sputtering yield for the oblique ion incidence near the edge. Axial asymmetry of the erosion and growth rate distributions may be due to the asymmetry of the electric field lines at the periphery of the target, which leads to a nonuniform incidence angle along the edge. In contrast to erosion and growth rates, the redeposition rate of sputtered atoms onto the target is found to increase considerably with pressure. © 1996 American Vacuum Society View full abstract»

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  • Reactive magnetron sputter deposition of polycrystalline vanadium nitride films

    Page(s): 3124 - 3129
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    Polycrystalline vanadium nitride films were deposited onto M2 steel substrates using a high‐rate reactive dc magnetron sputtering system by sputtering vanadium metal in an Ar+N2 atmosphere under N2 partial pressure control. The crystal structure, surface morphology, and properties of the films were affected by several process parameters such as nitrogen partial pressure, target power, and negative substrate bias. Analytical techniques including x‐ray diffraction and scanning electron microscopy were used to characterize the structure and morphology of the films, and the mechanical properties of the films were measured by a Vickers microhardness and a scratch adhesion testers. The nitrogen partial pressure was found to be the dominant deposition parameter for the formation of different phases which includes crystalline V metal, hexagonal β‐V2Nx, and cubic δ‐VNx, amorphous V–Nx solid solution, and their mixtures. The film hardness was affected by crystalline phase, and a maximum hardness of 3000 kgf/mm2 Hv0.05 was found at the β‐V2Nx phase. The morphology of the films varied in a wide range from cauliflowerlike rough and porous surface to smooth and dense surface, and can be correlated to deposition parameters. © 1996 American Vacuum Society View full abstract»

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  • Laser desorption study of deuterium implanted in silicon carbide

    Page(s): 3130 - 3134
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    Laser desorption of deuterium implanted in hot‐pressed silicon carbide samples was performed. The samples had been implanted at ion energies ranging from 1 keV/D to 3 keV/D and at fluences from 0.6×1020 m-2 to 1.8×1021 m-2. For the high fluence samples (≥3×1020 m-2), comparison of the experimental data of desorption rate versus laser energy with the results of computer simulations reveals that second order detrapping is the limiting re‐emission process. The effective trap activation energy decreases from 0.9±0.1 eV/molecule at 1 keV/D to 0.5±0.1 eV/molecule at 3 keV/D. Blister formation and exfoliation or other forms of radiation damage could explain the energy dependence in the high fluence samples. At low fluence (≪3×1020 m-2), most of the D2 re‐emission takes place above the melting threshold (12 kJ/m2). Computer simulations, using the thermal properties of the solid phase of SiC extrapolated above the melting point, give information about the nature of the detrapping process. A first order detrapping mechanism with an activation energy of 2.0±0.2 eV was found under those conditions. A comparaison is made with the deuterium laser desorption behaviour in Be, C and Si. © 1996 American Vacuum Society View full abstract»

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  • Chemical bonding and electronic properties of Se‐rich ZnSe–GaAs(001) interfaces

    Page(s): 3135 - 3143
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    We report synchrotron radiation, soft‐x‐ray photoemission spectroscopy studies of ZnSe–GaAs heterojunctions fabricated by molecular beam epitaxy in situ on GaAs(001)2×4 substrates. Measurements of the band offsets confirm that interfaces grown in Se‐rich conditions exhibit relatively low valence band offsets (as low as 0.5 eV), while interfaces grown in Zn‐rich conditions show relatively high valence band offsets (as high as 1.3 eV). In the Se‐rich case, the improved surface sensitivity of the technique revealed previously unreported contributions to the As 3d and Ga 3d core lineshapes, with substantial (0.8–2 eV) chemical shifts. The shifts, as well as the coverage and escape‐depth dependence of the results suggest enhanced atomic intermixing across Se‐rich interfaces, with the formation of both Se–As and Se–Ga chemical bonds. © 1996 American Vacuum Society View full abstract»

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  • Formation of titanium nitride coatings by nitrogen plasma immersion ion implantation of evaporated titanium films

    Page(s): 3144 - 3146
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    Titanium was deposited onto silicon by electron beam evaporation in high vacuum. The Ti films were treated by plasma immersion ion implantation (PIII) with energetic nitrogen ions extracted from a plasma which was generated by electron cyclotron resonance microwave excitation. The elemental composition of the films was measured by Rutherford backscattering spectrometry and the different phases were identified by x‐ray diffraction. The results show that nitrogen PIII treatment leads to nitrogen ion incorporation with nitride phase formation, accompanied by an increase in density. Two mechanisms for the incorporation of nitrogen can be distinguished: implantation and radiation enhanced diffusion. © 1996 American Vacuum Society View full abstract»

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  • Optical emission spectroscopy from arc‐like Ti vapor plasma and effects of self‐ion bombardment on Ti and TiN film deposition

    Page(s): 3147 - 3155
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    Arc‐like Ti vapor plasma is formed on the electron beam evaporation source by applying low dc voltage to the anode near the source in high vacuum. This plasma spectrum consists of Ti I (neutral) and Ti II (Ti+) lines. However no emission lines of nitrogen are observed with nitrogen gas inflow up to 1.3×10–1 Pa. This suggests that the dominant ion species is Ti+. Ti and TiN films are deposited on the water‐cooled and non‐cooled substrates at anode current 60 A. When negative substrate voltage (Vs) increases from 0 to 1000 V, substrate current density at 0.34 m from the source increases from 60 to 90 A/m2. Ion‐to‐Ti impinging flux ratio is estimated to be ∼1.35 at Vs=0 V. Deposition rates of 4 nm/s (Ti film) and 3 nm/s (TiN film) at Vs=0 V decrease largely in the former case and slightly in the latter case with increasing Vs. That is, self‐sputter yield of the former is larger than that of the latter. The former varies with, and the latter is independent of substrate temperature. N/Ti ratio in TiN film is close to unity for the noncooled substrate. On the other hand, N/Ti ratio decreases from 0.9 to 0.7 with δ TiN single phase for the water‐cooled substrate with increasing Vs. These results are different from the reported results from low energy‐ion assisted deposition and reactive bias sputtering. This is attributed to the fact that self‐ion bombardment differs from N+2 and/or Ar+ bombardment. © 1996 American Vacuum Society View full abstract»

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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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Editor
G. Lucovsky
North Carolina State University