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Sep 2000

Volume 18, Issue 5, pp. 2045-2612

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Plasma etch/deposition modeling: A new dynamically coupled multiscale code and comparison with experiment

Michael J. Bear and John U. Guillory

J. Vac. Sci. Technol. A 18, 2045 (2000); http://dx.doi.org/10.1116/1.1285990 (8 pages) | Cited 7 times

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Next-generation plasma-process modeling tools can provide new insight into process dynamics by resolving the diverse length and time scales present in reactor systems. The length scales range from the size of the reactor (∼10 cm) to surface details (∼100 nm), and time scales from electron sheath-transit times (nanoseconds) to total process time (minutes). Other key features include dynamic coupling of the plasma and solid (particles and fields), and the ability to model realistic surface interactions (deposition, etch, sputter, polymerization, etc.). A computational tool has been developed which provides all of these features through the coupling of heterogeneous code modules [hybrid plasma, particle in cell (PIC) plasma and solid surface chemistry] and through time-sampling techniques. The hybrid code (particle ions, fluid electrons) provides the basis for modeling the large-scale plasma reactor using a finite-element mesh to represent complex reactor geometries. The PIC code is used in the dynamic sheath boundary region to account for electron movement. The solid surface chemistry code is specially developed to model complex interactions between surface mechanisms, such as the formation of polymer and its possible removal by high-energy particles. The solid surface module uses a finite element scheme with adaptive mesh refinement (on a many-cycle time scale) to follow the complex surface evolution. These code modules exchange information on a sub-rf-period timescale, allowing for direct solid/plasma interactions. The long process times (minutes) are simulated by result sampling and using the slow evolution of the plasma/solid system. The code also performs surface charge migration and local gas heating to more completely represent the physical processes occurring in a plasma processing operation. The modeling of plasma processing must also account for the multilayer films and many species of particles and material types. The incorporation of this information in the simulations has demonstrated mask erosion. The simulations performed using this code have also shown good correlation to experimental results for steady state etch rates, etch rates as a function of via size, sidewall polymer evolution, and the production of “sputter wind” and surface charging. In deposition mode, the simulations demonstrate the experimentally observed polymer and deposited film topology. © 2000 American Vacuum Society.
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52.65.-y Plasma simulation
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
07.05.Tp Computer modeling and simulation
02.70.Dh Finite-element and Galerkin methods
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.65.Cf Surface cleaning, etching, patterning
52.40.Hf Plasma-material interactions; boundary layer effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.35.-x Polymers: properties; reactions; polymerization
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Analysis of chlorine-containing plasmas applied in III/V semiconductor processing

Gerhard Franz, Agnes Kelp, and Peter Messerer

J. Vac. Sci. Technol. A 18, 2053 (2000); http://dx.doi.org/10.1116/1.1286072 (9 pages) | Cited 14 times

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Capacitively coupled discharges of strongly reactive atmospheres containing mixtures of boron trichloride and chlorine are investigated with optical emission spectroscopy and self-excited electron resonance spectroscopy. This analyzes the whole area spanned by these gases and their impact on important plasma parameters like plasma density, electron temperature, and electron collision rate with neutrals. Using these data, roughly calculated cross sections for these gases are obtained in the low-energy region. Molecular chlorine ions, Cl2+, are evidently present to a preponderant amount as a main agent, which are accompanied by chlorine radicals, Cl(I), in mixtures with chlorine. Absolutely no chlorine ions could be found in the plasma which referred to the effective cooling of the Cl-containing species rather than the nonexistence of these species. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Effect of magnetic field configuration in the cathodic polymerization systems with two anode magnetrons

J. G. Zhao and H. K. Yasuda

J. Vac. Sci. Technol. A 18, 2062 (2000); http://dx.doi.org/10.1116/1.1286548 (5 pages) | Cited 2 times

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Direct current glow discharge can be utilized in plasma polymer coating of metal substrates by using the substrate as the cathode (cathodic polymerization). By using an anode equipped with magnetic enhancement, the anode magnetron cathodic polymerization can be effectively operated in low pressure regime, in which a tight barrier type plasma polymer can be formed. When two magnetrons are used against a cathode (substrate), the configurations of magnetic field employed in each magnetron become an important factor of the system. In one case [parallel magnetron (PM)], in which the identical magnetrons are used; magnetic field near the substrate (cathode) emanating from two magnetrons are parallel. In another case [opposite magnetron (OM)], in which magnet arrangement is reversed in one magnetron, magnetic fields near the substrate are opposite. Plasma polymerization with no magnetron shows the edge effect (higher deposition rate near the edge of cathode). With anode magnetrons (OM or PM), the edge effect is eliminated and higher deposition rates, compared to that obtained without magnetron, were obtained in the majority of electrode area. The uniformity of the deposition rate distribution is better with the OM configuration than with the PM configuration. The distance between electrodes influences the distribution of the deposition rate with the PM configuration (less uniform with small distance), but has little effect with the OM configuration. The advantage of having anode magnetrons diminishes at system pressure higher than 50 mTorr. © 2000 American Vacuum Society.
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82.35.-x Polymers: properties; reactions; polymerization
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona

The role of feedgas chemistry, mask material, and processing parameters in profile evolution during plasma etching of Si(100)

J. M. Lane, K. H. A. Bogart, F. P. Klemens, and J. T. C. Lee

J. Vac. Sci. Technol. A 18, 2067 (2000); http://dx.doi.org/10.1116/1.1286025 (13 pages) | Cited 5 times

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Profile evolution of trenches and lines, both nested and isolated, during etching with Cl2, HBr, and HCl plasmas in a high density, commercial etch tool was investigated. Features patterned with and without an insulating SiO2 mask layer produced similar profiles with Cl2 and HCl plasma etching, but markedly different profiles with HBr plasma etching. The contribution of the SiO2 mask material to sidewall passivation is discussed. Under certain plasma conditions without a SiO2 mask, severe facets on the silicon lines were observed. The importance and relevance of this facet formation to the profile evolution process is reviewed. Profile evolution with increasing reactor pressure was identical during etching with HBr and Cl2 plasma etching, although the profiles etched in either gas at the same pressure were markedly different. These experimental results are compared to plasma etching models and molecular beam experiments reported in the literature, and the contribution of these data to feature profile evolution simulators is presented. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Rv Passivation
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
85.40.Hp Lithography, masks and pattern transfer

Etching of (Ba,Sr)TiO3 film by chlorine plasma

Teruo Shibano, Takashi Takenaga, Keisuke Nakamura, and Tatsuo Oomori

J. Vac. Sci. Technol. A 18, 2080 (2000); http://dx.doi.org/10.1116/1.1286026 (5 pages) | Cited 7 times

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Experimental studies of the etching of (Ba,Sr)TiO3 (BST) have been performed in Ar/halogen and Cl2 plasmas. In spite of the poor volatility of halogenated barium and strontium, some chemical enhancement of the etching reaction was observed in the etching of BST with halogen-containing plasmas. An investigation of the etching of BaOx, SrOx, TiOx, and BaxSryOz films with Cl2 plasma showed that the chemical enhancement in BST etching was related to the existence of titanium in BST films. The chemical reactivity of titanium with chlorine seemed to enhance the etching of BST. In the x-ray photoelectron spectroscopy analysis of the BST surfaces etched with Cl2 plasma, we found that barium- and strontium-rich surfaces were formed during the etching and that etching residues consisting of barium and strontium were observed after the BST films were etched off. © 2000 American Vacuum Society.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.65.Cf Surface cleaning, etching, patterning
77.55.-g Dielectric thin films
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Crystallization of amorphous-silicon films with seed layers of microcrystalline silicon by plasma heating

Hae-Yeol Kim, Chan-Do Park, Youn-Seon Kang, Kuk-Jin Jang, and Jai-Young Lee

J. Vac. Sci. Technol. A 18, 2085 (2000); http://dx.doi.org/10.1116/1.1289538 (5 pages) | Cited 4 times

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A novel solid-phase crystallization method is suggested for synthesizing large-grained polycrystalline silicon (poly-Si) films at low temperature (∼500 °C) and in a short time (1 h). Hydrogenated microcrystalline-silicon (μc-Si:H) and hydrogenated amorphous-silicon (a-Si:H) layers are sequentially deposited on a glass substrate in order to form a-Si:H/μc-Si:H bilayers before annealing through conventional furnace heating and a new annealing method, plasma heating, respectively. It is found that the crystallization rate of the bilayers during the plasma heating is much higher than that of the bilayers during the furnace heating. Moreover, the crystallization reaction is enhanced more effectively during the annealing in the case of the bilayers which are hydrogen-plasma treated between the depositions of μc-Si:H and a-Si:H layers than in the case of those which are not. Finally, poly-Si films with grains of ∼0.4 μm are obtained through the plasma heating method combined with the hydrogen-plasma treatment. © 2000 American Vacuum Society.
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81.05.Gc Amorphous semiconductors
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Cy Elemental semiconductors

Etching of Si through a thick condensed XeF2 layer

P. G. M. Sebel, L. J. F. Hermans, and H. C. W. Beijerinck

J. Vac. Sci. Technol. A 18, 2090 (2000); http://dx.doi.org/10.1116/1.1288194 (8 pages) | Cited 3 times

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Etching of silicon by XeF2 is studied in a multiple-beam setup. Below 150 K XeF2 condenses and forms a layer on the silicon, which blocks the etching. Upon ion bombardment, this layer is removed and etching will resume. As a function of the layer thickness, the various removal mechanisms of the layer are studied. For a thick condensed layer it is found that 1 keV Ar+ ions sputter the condensed layer with a yield of 160 XeF2 molecules per ion for 1 keV Ar+ ions and 280 for 2 keV ions. For thinner layers (below 9 nm for 1 keV ions), this sputter rate by ions decreases significantly. Here, the removal is mainly due to consumption of XeF2 by etching at the bottom of the layer. This consumption rate reaches a maximum for a layer thickness of about 5 nm. In the steady-state situation, the layer thickness is further decreased, resulting in a smaller consumption and etch rate. Here, sputtering is the most important removal mechanism for the deposited XeF2 layer. From this, it is concluded that a pulsed ion beam should be used in cryogenic etching to obtain the highest etch rate. © 2000 American Vacuum Society.
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81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning

Characteristics of ZnO:Cr thin films deposited by spray pyrolysis

A. Maldonado, M. de la L. Olvera, R. Asomoza, and S. Tirado-Guerra

J. Vac. Sci. Technol. A 18, 2098 (2000); http://dx.doi.org/10.1116/1.1287444 (4 pages) | Cited 2 times

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Chromium-doped zinc oxide thin films were deposited using the spray pyrolysis technique. In all cases 15 at. % of chromium in solution was used. Under diluted HCl, a low etching rate in ZnO:Cr thin films is obtained, as compared to undoped ZnO. As-deposited and vacuum-annealed films show a high resistivity. X-ray diffraction spectra show no extra phases present. A low incorporation efficiency of chromium into the ZnO films is observed, and less than 1 at.% chromium is present in the films and (002) preferential growth is observed in all cases. High transmittance is obtained, which makes films adequate for transparent and protective coatings. © 2000 American Vacuum Society.
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81.05.Dz II-VI semiconductors
81.15.Rs Spray coating techniques
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.65.Cf Surface cleaning, etching, patterning
42.79.Wc Optical coatings

Gas utilization in remote plasma cleaning and stripping applications

B. E. E. Kastenmeier, G. S. Oehrlein, John G. Langan, and William R. Entley

J. Vac. Sci. Technol. A 18, 2102 (2000); http://dx.doi.org/10.1116/1.1287442 (6 pages) | Cited 14 times

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Nitrogen trifluoride (NF3) is a likely candidate to replace perfluorocompounds (PFCs) in stripping and reactor cleaning applications. In this article, the performance of NF3 for the etching of silicon, silicon dioxide (SiO2), and silicon nitride (Si3N4) is compared with that of CF4, C2F6, and C3F8. The performance measures emphasized in this article are the dissociation efficiency of the parent molecule in the discharge, the etch rate, and the gas utilization. The destruction efficiency of NF3 in the discharge as determined by mass spectrometry is typically 100%. The maximum destruction of the PFC gases for the parameters used in this investigation is approximately 75% for CF4, and can approach 100% for C2F6 and C3F8. The removal rates for NF3 obtained at optimum settings of O2 addition and microwave power are significantly higher than those for PFC gases. The gas utilization, which describes the degree of conversion of the parent molecules into etch products and is defined in this article, is also higher for NF3 than for the other gases investigated. © 2000 American Vacuum Society.
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81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Plasma injection with helicon sources

Francis F. Chen, Xicheng Jiang, and John D. Evans

J. Vac. Sci. Technol. A 18, 2108 (2000); http://dx.doi.org/10.1116/1.1289537 (8 pages) | Cited 12 times

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An exhaustive set of measurements has been made to find the optimum conditions for plasma injection into a processing chamber using small helicon sources with low magnetic fields B. It is found that the plasma density decreases, rather than increases, with B, as in normal helicon discharges. The design of the field coil and flange caused this effect; with a different design, normal operation was obtained. This experiment provides data on the area coverage of individual helicon discharges for the design of large-area, distributed plasma sources. © 2000 American Vacuum Society.
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52.50.Dg Plasma sources
52.25.-b Plasma properties

Powder formation in germane–silane plasmas

R. A. C. M. M. van Swaaij, B. S. Girwar, and J. W. Metselaar

J. Vac. Sci. Technol. A 18, 2116 (2000); http://dx.doi.org/10.1116/1.1286022 (6 pages) | Cited 1 time

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The powder formation in a germane (GeH4)–silane (SiH4) plasma was investigated for a range of deposition parameters used in the processing of amorphous silicon devices, in particular the pressure, p, and the total gas flow, ϕ. For that purpose the plasma was monitored continuously by measuring the dc self-bias, Vsb, as a function of time. At certain plasma conditions oscillations in the self-bias are observed. In literature these oscillations have been related to the spatial oscillation of the powder-forming region in the plasma and they can be used as an indication of the so-called α–γ′ transition of the plasma, i.e., the moment at which powder formation starts to occur in the plasma. Changes in the plasma are monitored by measuring the amplitude of the oscillations of the self-bias, ΔVsb. It was found that the dependence of ΔVsb on p can be divided into three ranges: (i) low-pressure range in which ΔVsb is small; (ii) medium-pressure range in which ΔVsb varies significantly and powder is formed in the plasma; and (iii) high-pressure range in which the plasma is visually unstable. The pressure at which the transition from range (i) to (ii) occurs is indicative for the α–γ′ transition and appears to depend on the gas composition, in particular the [GeH4]/[SiH4] flow ratio. This ratio also determines the rate of powder formation. We argue that the production of GeH2 radicals is responsible for this formation. In addition we conclude that the α–γ′ transition is determined by the partial pressure of SiH4 plus GeH4 and is not dependent on the residence time of the gas in the reaction chamber. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
68.55.-a Thin film structure and morphology

Fluorocarbon polymer deposition kinetics in a low-pressure, high-density, inductively coupled plasma reactor

M. J. Sowa, M. E. Littau, V. Pohray, and J. L. Cecchi

J. Vac. Sci. Technol. A 18, 2122 (2000); http://dx.doi.org/10.1116/1.1286396 (8 pages) | Cited 25 times

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Maintaining dimensional control and adequate throughput during the etching of submicron features requires plasma etch tools that operate at low pressures and high densities, such as inductively coupled plasmas (ICPs). Unfortunately, in this regime, it has proven difficult to achieve a stable, reproducible chemistry for selective oxide etching of contacts and vias. In particular, it is difficult to control the passivating polymer film which provides etching selectivity to silicon, nitride, and photoresist. As a first step toward sorting out the complicated oxide etching chemistry, we have measured and modeled the kinetics of the polymer film deposition in an ICP reactor for C2F6/H2 and CHF3 chemistries. Using a unique application of statistical design of experiments, we have explored the pressure range of 3–15 mTorr, power range of 300–2000 W, residence times from 0.5 to 1.0 s, and magnetic field from 0 to 24 G. Polymer deposition rates on a bare Si wafer are measured using a laser interferometer. The concentration of fluorocarbon radicals, CF, CF2, and CF3, are measured in the plasma using wavelength modulated infrared diode laser absorption spectroscopy. Additional measurements include actinometric F atom density and ion saturation current. These measurements are analyzed in terms of a polymer deposition model and the important physical phenomena are inferred. Significantly, we find a unique polymer deposition mechanism over the entire range of tool parameters including direct deposition of CF and ion-assisted deposition of CF2. © 2000 American Vacuum Society.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.25.-b Plasma properties
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
81.65.Cf Surface cleaning, etching, patterning
78.30.Jw Organic compounds, polymers
78.66.Qn Polymers; organic compounds

Sensitivity studies of silicon etching in chlorine/argon plasmas

S. Kleditzsch and U. Riedel

J. Vac. Sci. Technol. A 18, 2130 (2000); http://dx.doi.org/10.1116/1.1285997 (7 pages) | Cited 2 times

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In this article a well-stirred reactor model is utilized to model the etching of silicon in low-pressure chlorine/argon plasmas. Well-stirred reactor models are increasingly common in the literature due to their low requirements of computer resources for detailed chemical kinetics calculations. The model predicts the spatially averaged species composition and etch rate in a plasma etch reactor by solving conservation equations for species, mass, and the electron energy distribution function (EEDF). The reactor is characterized by a chamber volume, surface area, surface area fraction of the wafer, mass flow, pressure, power deposition, and composition of the feed gas. In such plasma etch models, assumptions on the EEDF which are needed to determine reaction rate coefficients for electron-impact reactions, are crucial for a prediction of steady state conditions. The model presented in a recent article [P. Ahlrichs, U. Riedel, and J. Warnatz, J. Vac. Sci. Technol. A 16, 1560 (1998)] is extended to describe the etching of the wafer with a special set of reactions occurring on a certain area fraction of the total reactor surface. A modified numerical procedure to solve the species conservation equations and the EEDF is presented, which needs considerably less computation time than the approach previously taken. Systematic sensitivity studies are presented to identify the connection between input parameters, outflow composition, and etch rate of the process. Such numerical studies are an important step towards fault detection and model based process control of plasma reactors. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.20.-w Chemical kinetics and dynamics
02.60.-x Numerical approximation and analysis
81.05.Cy Elemental semiconductors

Interactions between plasmas in ionized physical vapor deposition discharges

Y. Andrew, Z. Lu, T. Snodgrass, G. Teitzel, and A. E. Wendt

J. Vac. Sci. Technol. A 18, 2137 (2000); http://dx.doi.org/10.1116/1.1286360 (6 pages) | Cited 3 times

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Ionized physical vapor deposition is of current interest for the thin film deposition of diffusion barriers and copper seed layers for interconnect metallization. Experimental evidence of the interaction between the magnetron discharge and the inductively coupled plasma leading to lower plasma potentials and direct current bias voltages than expected is presented. Such effects have major implications for radio frequency coil lifetimes, discharge uniformity, and simulations of such discharges. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
85.40.Sz Deposition technology
52.65.-y Plasma simulation
85.40.Ls Metallization, contacts, interconnects; device isolation
52.70.Gw Radio-frequency and microwave measurements

Investigation of Si-doped diamond-like carbon films synthesized by plasma immersion ion processing

X. M. He, K. C. Walter, M. Nastasi, S.-T. Lee, and M. K. Fung

J. Vac. Sci. Technol. A 18, 2143 (2000); http://dx.doi.org/10.1116/1.1286141 (6 pages) | Cited 19 times

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Silicon (Si)-doped diamond-like carbon (DLC) was prepared on Si(100) and polymethyl metha̱crylate (PMMA) substrates using a C2H2–SiH4–Ar plasma immersion ion processing (PIIP) method. The chemical composition of the films was varied by adjusting the reactive gas-flow ratio of SiH4 to C2H2 during PIIP depositions. The influence of the Si dopant on the bonding structure, stress, and properties of the DLC films was investigated by using ion beam analysis techniques, Raman shift, ultraviolet/visible spectroscopy, and by analyzing the measured properties. The incorporation of Si up to 17.3 at. % produced a reduction in film stress and increased the density and optical band gap. The Si-doped DLC films also exhibited increased sp3 bonding and higher hardness (25–28 GPa). Further increase in Si dopant, to above 22 at. %, caused a transformation from DLC to amorphous silicon carbide (a-SiC) that showed high hydrogen capacity, low hardness, and low stress. Pin-on-disk tribological tests of Si-doped DLC on PMMA showed greatly improved wear and friction properties related to the uncoated PMMA. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
78.66.Jg Amorphous semiconductors; glasses
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq Friction, lubrication, and wear

Studies on the optimum condition for the formation of a neutral loop discharge plasma

Y. M. Sung, K. Uchino, K. Muraoka, and T. Sakoda

J. Vac. Sci. Technol. A 18, 2149 (2000); http://dx.doi.org/10.1116/1.1286391 (4 pages) | Cited 14 times

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In order to obtain guidelines for the design and operation of a new plasma source by a magnetic neutral loop discharge, electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three-dimensional electromagnetic field with spatial decay of the rf electric field, and the limitation of the spatial extent of the electron motion (the existence of walls and the electron loss at wall surfaces). These factors were found to explain the existence of the optimum magnetic field gradient. © 2000 American Vacuum Society.
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52.50.Dg Plasma sources
52.80.Dy Low-field and Townsend discharges
52.40.Hf Plasma-material interactions; boundary layer effects

Film growth precursors in a remote SiH4 plasma used for high-rate deposition of hydrogenated amorphous silicon

W. M. M. Kessels, M. C. M. van de Sanden, and D. C. Schram

J. Vac. Sci. Technol. A 18, 2153 (2000); http://dx.doi.org/10.1116/1.1289541 (11 pages) | Cited 39 times

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The SiH4 dissociation products and their contribution to hydrogenated amorphous silicon (a-Si:H) film growth have been investigated in a remote Ar–H2–SiH4 plasma which is capable of depositing device-quality a-Si:H at 10 nm/s. SiH3 radicals have been detected by means of threshold ionization mass spectrometry for different fractions of H2 in the Ar–H2-operated plasma source. It is shown that at high-H2 flows, SiH4 dissociation is dominated by hydrogen abstraction and that SiH3 contributes dominantly to film growth. At low-H2 flows, a significant amount of very reactive silane radicals, SiHx(x⩽2), is produced, as concluded from threshold ionization mass spectrometry on SiH2 and optical emission spectroscopy on excited SiH and Si. These radicals are created by dissociative recombination reactions of silane ions with electrons and they, or their products after reacting with SiH4, make a large contribution to film growth at low-H2 flows. This is corroborated by the overall surface reaction probability which decreases from ∼0.5 to ∼0.3 with increasing H2 fraction. The film properties improve with increasing H2 flow and device-quality a-Si:H is obtained at high H2 fractions where SiH3 dominates film growth. Furthermore, it is shown that at high-H2 flows the contribution of SiH3 is independent of the SiH4 flow while the deposition rate varies over one order of magnitude. © 2000 American Vacuum Society.
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81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Nc Particle measurements
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Effects of plasma excitation power, sample bias, and duty cycle on the structure and surface properties of amorphous carbon thin films fabricated on AISI440 steel by plasma immersion ion implantation

Z. M. Zeng, X. B. Tian, T. K. Kwok, B. Y. Tang, M. K. Fung, and P. K. Chu

J. Vac. Sci. Technol. A 18, 2164 (2000); http://dx.doi.org/10.1116/1.1285996 (5 pages) | Cited 3 times

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Plasma immersion ion implantation is a nonline-of-sight method for fabricating amorphous carbon or diamond-like-carbon coatings on steels to improve the surface properties. In this work, carbon thin films are synthesized on 9Crl8 (AISI440) stainless bearing steel by acetylene (C2H2) plasma immersion ion implantation (PIII). The effects of the processing parameters, including rf power, sample voltage pulse duty cycle, and target bias, on the structure and surface properties of the carbon thin films is systematically investigated employing Raman spectroscopy, Auger electron spectroscopy, friction coefficient measurement, and wear test. The results reveal that carbon films several hundred nanometers thick with a well-mixed interface are formed on the 9Crl8 steel after C2H2 PIII, but the structure and properties of the carbon films vary greatly under different PIII conditions. There is an optimal process window within which the synthesized films have superior properties, and current densities that are too high do not yield films with the desired performance. © 2000 American Vacuum Society.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
61.72.up Other materials
61.80.Jh Ion radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.70.-q Methods of materials testing and analysis
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Cl2-based dry etching of GaN films under inductively coupled plasma conditions

Y. H. Im, J. S. Park, Y. B. Hahn, K. S. Nahm, Y-.S. Lee, B. C. Cho, K. Y. Lim, H. J. Lee, and S. J. Pearton

J. Vac. Sci. Technol. A 18, 2169 (2000); http://dx.doi.org/10.1116/1.1286363 (6 pages) | Cited 10 times

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Dry etching of undoped, n- and p-type GaN films was carried out in Cl2-based inductively coupled plasmas (ICPs) using different rf excitation frequencies of 100 kHz and 13.56 MHz, in which the rf chuck power source operates. The etch rates with lower frequency of 100 kHz are somewhat greater than those with a higher frequency of 13.56 MHz due to higher ion bombarding energy with lower frequency. The highest etch rates with the 100 kHz frequency were obtained at moderately high ICP power of 700 W: ∼9300 Å/min of n-GaN, ∼5300 Å/min of p-GaN, and ∼7100 Å/min of undoped GaN. The 13.56 MHz frequency of rf chuck power source produced maximum etch rates of ∼7900 Å/min of n-GaN, ∼5800 Å/min of p-GaN, and 6100 Å/min of undoped GaN at 20 mTorr, 700 W ICP, and 150 W rf power. The surface roughness was relatively independent of the chuck power up to 150 W in 13.56 MHz and showed fairly smooth morphology (rms 1.1–1.3 nm), while etching at higher rf power (>200 W) produced rougher surface. © 2000 American Vacuum Society.
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81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
68.55.-a Thin film structure and morphology
82.20.Pm Rate constants, reaction cross sections, and activation energies
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Investigation of dilute SF6 discharges for application to SiC reactive ion etching

J. D. Scofield, B. N. Ganguly, and P. Bletzinger

J. Vac. Sci. Technol. A 18, 2175 (2000); http://dx.doi.org/10.1116/1.1286361 (10 pages) | Cited 9 times

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Impedance matching and power coupling efficiency optimization of SF6 gas discharges diluted with Ar and He have been compared in relation to reactive ion etch rates and etched feature anisotropy of hexagonal (6H) silicon carbide (SiC). In contrast to the measured radio frequency (rf) power coupling efficiency, He diluted mixtures resulted in greater etch rates by up to 50%, with superior anisotropy and surface morphology than comparable Ar:SF6 mixtures. The superior etched surface finish for the He diluted mixtures possibly arises from the less severe sputtering damage of SiC for He+ and SFX+, compared to Ar+ with the same energy. Etch rates over 3300 Å/min have been achieved with excellent surface morphologies and anisotropy. These results conflict with the notion that Ar+ ions are expected to enhance the ion assisted etch mechanism in technical gas mixtures. We observed superior, SiC etch performance for He:SF6 mixtures, compared to Ar:SF6, over the entire 10%–90% fractional ratios investigated. This result appears to be due to differing bulk discharge chemistries which control the flux of radicals and ions to the substrate, resulting in optimal surface polymerization conditions. This suggestion is based on our estimated bulk E/n values, known partial ionization cross sections, production rate coefficients for SF3+ and SF5+, and higher electron energy distributions for He dilution. In addition, we provide further evidence for the generic nature of utilizing the complex electrical characteristics of the rf discharge to optimize plasma etch conditions. On the other hand, we have demonstrated that understanding the details of gas phase kinetics is also necessary to fully exploit the power coupling optimization scheme for rf discharges, which are specific to the gas mixtures being utilized. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.05.Hd Other semiconductors
52.80.Dy Low-field and Townsend discharges
82.35.-x Polymers: properties; reactions; polymerization
68.35.B- Structure of clean surfaces (and surface reconstruction)

Hysteresis and mode transitions in a low-frequency inductively coupled plasma

S. Xu, K. N. Ostrikov, W. Luo, and S. Lee

J. Vac. Sci. Technol. A 18, 2185 (2000); http://dx.doi.org/10.1116/1.1286142 (13 pages) | Cited 44 times

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Global electric properties, distributions of the induced electromagnetic fields, electron density, temperature, and plasma potential in the 500 kHz planar-coil inductively coupled plasma source have been investigated. The transitions between the two (E and H) discharge operating regimes with variation of input power and operating gas pressure have been demonstrated. It has been shown that the E↔H transitions are accompanied by the resonant minima in the rf power reflection coefficient, which are characteristic for mode jumps in electron cyclotron resonance and microwave slot-excited discharges. The optical emission spectra of argon atoms and ions together with global power balance arguments suggest that the step-wise ionization via the excited states of argon atoms and ions is presumably a mechanism which is responsible for hysteresis. The achieved high plasma density with a high homogeneity level, and low electron temperature and plasma potential imply that the studied plasma source is promising for industrial applications. © 2000 American Vacuum Society.
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52.25.-b Plasma properties
52.50.Dg Plasma sources
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Particle transport in a parallel-plate semiconductor reactor: Chamber modification and design criterion for enhanced process cleanliness

Sandeep Nijhawan, Peter H. McMurry, and Stephen A. Campbell

J. Vac. Sci. Technol. A 18, 2198 (2000); http://dx.doi.org/10.1116/1.1288193 (9 pages) | Cited 9 times

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Convective, diffusive, and thermophoretic particle transport in a parallel-plate semiconductor reactor is investigated. Measurements that illustrate particle transport in the reactor are presented and a Eulerian continuum particle transport formulation is used to quantitatively explain the measurements. Experimental and numerical results show that particles formed in the parallel-plate region are confined in a thin sheath (∼2 cm) between the “hot” wafer and “cold” showerhead inlet. This sheath is located at the point where downward convective transport balances upward transport by thermophoresis. The particle sheath location is independent of particle size but is dependent on gas flow rates and temperature of the wafer and showerhead inlet. In addition, experimental and numerical results show that as particles exit the parallel-plate region, the radial thermophoretic particle transport can produce “ring-like” contaminant deposits on the outer wall of the reactor under certain flow conditions. We propose a simple reactor design modification and an analytic design criterion to avoid particle deposition on the chamber walls. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
47.11.-j Computational methods in fluid dynamics
47.27.T- Turbulent transport processes
47.70.Fw Chemically reactive flows

Electron temperature, density, and metastable-atom density of argon electron–cyclotron-resonance plasma discharged by 7.0, 8.0, and 9.4 GHz microwaves

Y. Kawai, K. Kano, T. Suzuki, H. Akatsuka, and Y. Fujii

J. Vac. Sci. Technol. A 18, 2207 (2000); http://dx.doi.org/10.1116/1.1289542 (6 pages) | Cited 3 times

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The characteristics of argon plasma discharged by electron–cyclotron resonance (ECR) with the microwave frequencies of 7.0, 8.0, and 9.4 GHz are investigated in the pressure range of 0.013–0.13 Pa, where the magnetic field was adjusted to keep the ECR point at the same position. The input power of the microwave was set at 10 and 50 W. Plasma densities and the electron temperatures were found to be almost independent of the microwave frequency at low pressure. The dependence of the electron density on the microwave frequencies becomes apparent in the higher-pressure range above 0.080 Pa. In the case that the discharge power is 50 W, the plasma operated using 9.4 GHz microwave showed the highest electron density and the plasma operated using 7.0 GHz had the lowest electron density. Metastable-atom densities were estimated by using a collisional radiative model. The mestable-atom densities, ∼1017 m−3, are lower than the electron density ∼1018 m−3 at the discharge power of 50 W, whereas these densities were comparable at the discharge power of 10 W. © 2000 American Vacuum Society.
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52.70.Gw Radio-frequency and microwave measurements
52.25.Kn Thermodynamics of plasmas
52.80.Pi High-frequency and RF discharges

Diagnosis of positive ions from the near-cathode region in a high-voltage pulsed corona discharge N2 plasma

Shukai Tang, Wenchun Wang, Jiahong Liu, Xuefeng Yang, and Yan Wu

J. Vac. Sci. Technol. A 18, 2213 (2000); http://dx.doi.org/10.1116/1.1286362 (4 pages) | Cited 12 times

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Positive ions from the near-cathode region in a wire-plate high-voltage pulsed corona discharge nitrogen plasma were characterized using a molecular beam mass spectrometer under severe electromagnetic interference. The N+ current is 2–8 times greater than that of N2+ at N2 pressure of 5–25 Torr, peak voltage of 4–10 kV, and repetition rate of 10–70 Hz. The nitrogen ion signals rise with increasing peak voltage and repetition rate of pulsed discharge, but exhibit a clear peak over the N2 pressure range studied. The kinetics of the physicochemical processes involved in the earlier N2 plasma has been studied. Nitrogen ion generation near the corona wire area and migration path to the cathode plate are the key areas in the understanding the phenomenon and mechanisms that are involved. © 2000 American Vacuum Society.
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52.80.Hc Glow; corona
52.70.Nc Particle measurements
07.75.+h Mass spectrometers

Abatement of C2F6 in rf and microwave plasma reactors

Steven A. Vitale and Herbert H. Sawin

J. Vac. Sci. Technol. A 18, 2217 (2000); http://dx.doi.org/10.1116/1.1286199 (7 pages) | Cited 5 times

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Experimental results in a low temperature, low power density rf plasma reactor show that C2F6 can be decomposed by plasma reaction with oxygen, but CF4, an undesirable byproduct, is produced. Previously, it had been shown in a high temperature, high power density microwave reactor that C2F6 can be decomposed without CF4 formation. Calculations show that low temperature neutral species kinetics favor the formation of CF4 over COF2, while the opposite is true at high temperature. Further, a high degree of feedstock dissociation such as that observed in high density plasma reactors is predicted to lead to very little CF4 formation. Calculations show that adding hydrogen, water, or hydrocarbons to the C2F6+O2 mixture should reduce the power necessary for abatement, and will reduce CF4 formation. Hydrogen is predicted to getter atomic fluorine to form thermodynamically stable HF, and thus prevent perfluorocompound reformation. © 2000 American Vacuum Society.
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52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.25.-b Plasma properties

Si etching rate calculation for low pressure high density plasma source using Cl2 gas

Young D. Lee, H. Y. Chang, and C. S. Chang

J. Vac. Sci. Technol. A 18, 2224 (2000); http://dx.doi.org/10.1116/1.1286197 (6 pages) | Cited 2 times

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Based on a simplified Cl2 plasma Si etching mechanism, we calculate the Si etching rate with a comprehensive analysis of the effect of ion bombardment. With its flux distribution, the bombarding ions are regarded as the sum of independent monoenergetic beams (SIMB) approach. The Si etching rate is examined over the radio-frequency (rf) frequency (νrf) range from 1 to 20 MHz (0.1νpi≲νrf≲2νpi, where νpi is the ion plasma frequency) under the typical low pressure high density plasma condition. To consolidate the SIMB approach, the etching rate is compared with the result from the monoenergetic single ion beam approach. The difference in the Si etching rate between the two approaches is notable at a low rf frequency range. The effect of threshold energy on the Si etching mechanism is also investigated. We conclude that under a low rf frequency, for a precise etching property examination, the effect of the bombarding ions should be investigated through the SIMB approach. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Structural and mechanical characterization of fluorinated amorphous-carbon films deposited by plasma decomposition of CF4–CH4 gas mixtures

L. G. Jacobsohn, D. F. Franceschini, M. E. H. Maia da Costa, and F. L. Freire

J. Vac. Sci. Technol. A 18, 2230 (2000); http://dx.doi.org/10.1116/1.1289540 (9 pages) | Cited 33 times

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Fluorinated amorphous-carbon films (a-C:F:H) were deposited by low-power rf capacitively coupled plasma-enhanced chemical-vapor deposition using CH4–CF4 gas mixtures. Different series of films were deposited, changing one parameter at a time: the CF4 partial pressure from 0% to 100%, the self-bias voltage from −50 to −700 V, and the total deposition pressure from 5 to 15 Pa. The composition was determined by ion-beam analysis (IBA): Rutherford backscattering spectrometry, elastic recoil detection analysis, and nuclear reaction analysis. The atomic density of the films was evaluated by combining the IBA results with the thickness value measured by stylus profilometry. Film structure was investigated by infrared transmission and Raman scattering spectroscopies. The internal stress and Vickers hardness were also measured. For a fixed self-bias, the increase of the CF4 partial pressure leads to a higher fluorine incorporation and the decrease of both hardness and internal stress. The film microstructure changes from diamond-like to a polymer-like structure. The fluorine incorporation also increases with the self-bias, and fluorine-poor polymer-like films are deposited at low-bias voltage. Fluorine incorporation occurs at the expense of the hydrogen content in both cases, i.e., increasing the CF4 partial pressure or the self-bias. Finally, the role of ion bombardment during film growth on the mechanical and structure properties of the films is discussed. © 2000 American Vacuum Society.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.-d Chemical analysis and related physical methods of analysis
78.35.+c Brillouin and Rayleigh scattering; other light scattering
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Er deposition in the submonolayer range on weakly boron-doped Si(111) surface

F. Palmino, S. Pelletier, E. Ehret, B. Gautier, and J. C. Labrune

J. Vac. Sci. Technol. A 18, 2239 (2000); http://dx.doi.org/10.1116/1.1285934 (5 pages) | Cited 2 times

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Erbium silicide growth on weakly boron-doped Si(111) was studied by scanning tunneling microscopy. The reactivity and the strain of this √3×√3R30° surface are different from those observed on Si(111) 7×7. These interesting features allow us to study the erbium silicide growth on a new interface. We have observed, in the submonolayer range, the formation of a metastable 2√3×2√3R30° reconstruction and the nucleation of two kinds of stable two-dimensional ErSi2. © 2000 American Vacuum Society.
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68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
66.30.Ny Chemical interdiffusion; diffusion barriers
81.15.Aa Theory and models of film growth
81.15.Np Solid phase epitaxy; growth from solid phases
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Iron oxide thin films prepared by ion beam induced chemical vapor deposition: Structural characterization by infrared spectroscopy

F. Yubero, M. Ocaña, A. Justo, L. Contreras, and A. R. González-Elipe

J. Vac. Sci. Technol. A 18, 2244 (2000); http://dx.doi.org/10.1116/1.1286198 (5 pages) | Cited 8 times

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Iron oxide thin films as hematite (α-Fe2O3) have been prepared by ion beam induced chemical vapor deposition. Very compact and dense films are obtained by this procedure. The thin films have been grown by bombardment of the substrate surfaces with O2+ ions or mixtures of O2+ and Ar+ ions, while a volatile precursor of iron [i.e., Fe(CO)5] is dosed onto the substrate surface. In the latter case, Ar atoms are incorporated within the iron oxide lattice. Atomic force microscopy, Rutherford backscattering spectroscopy, and x-ray photoelectron spectroscopy were utilized to characterize the films’ surface morphology, stoichiometry and chemical state. The film structure has been analyzed by grazing angle x-ray diffraction (XRD) and infrared spectroscopies. In particular, infrared spectroscopy has permitted a thorough structural characterization of the films, even in the cases where XRD does not provide information about the structure. Thus, when O2+ ions are used for the synthesis, iron oxide thin films grow with a hematite structure with the c axis of the crystallites perpendicular to the film surface. However, when an Ar+/O2+ ion mixture is used, the thin films have a hematite structure with the c axis of the crystallites oriented parallel to the film surface. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Jj Ion and electron beam-assisted deposition; ion plating
78.66.Nk Insulators
75.70.Ak Magnetic properties of monolayers and thin films
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.30.Hv Other nonmetallic inorganics
61.66.Bi Elemental solids
61.66.Dk Alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)

Nickel precipitation at nanocavities in separation by implantation of oxygen

Miao Zhang, Xuchu Zeng, Paul K. Chu, R. Scholz, and Chenglu Lin

J. Vac. Sci. Technol. A 18, 2249 (2000); http://dx.doi.org/10.1116/1.1288138 (5 pages) | Cited 7 times

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The structures of nickel decorated cavities and Ni precipitates epitaxially grown in the nanocavity band in separation by implantation of oxygen (SIMOX) are studied. The nanocavities are generated in the silicon substrate of the SIMOX wafer by proton implantation followed by Ni implantation into the Si overlayer. Channeling Rutherford backscattering spectrometry results indicate that Ni implantation changes the crystalline Si overlayer into amorphous Si. After annealing at 1000 °C for 2 h, the amorphous Si evolves into a polycrystalline structure composed of NiSi2 and polycrystalline silicon. In the meantime, most of the nickel atoms diffuse through the buried oxide layer and are gettered by the nanocavity band. NiSi2 precipitates are observed both in the nanocavities and at the residual defects created by H implantation. The microstructure of the Ni precipitate depends on whether there are cavities nearby. Without cavities in the vicinity, dislocations are observed in the neighborhood of the precipitate, whereas no dislocation is detected around the precipitate when there are nanocavities in the neighborhood. The precipitation and gettering behavior can be explained by the gettering of Si interstitials to the microcavities and lowering of the nucleation barrier. © 2000 American Vacuum Society.
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61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
64.75.-g Phase equilibria
61.72.Cc Kinetics of defect formation and annealing
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
61.46.-w Structure of nanoscale materials

How low-energy ions can enhance depositions on low-K dielectrics

Peter Abramowitz, Michael Kiene, and Paul S. Ho

J. Vac. Sci. Technol. A 18, 2254 (2000); http://dx.doi.org/10.1116/1.1285933 (8 pages) | Cited 2 times

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Ultrathin titanium nitride layers grown on three different dielectrics were studied to examine how low-energy ions change the chemical composition at and near their interface. Comparisons were made by growing titanium nitride under similar conditions both with (ion-assisted) and without (reactive) nitrogen ions. Although the chemical reactions between the titanium nitride and the three dielectrics under both growth conditions depend on the type of dielectric used, a few general observations were seen. In comparison with the reactively grown samples, all of the ion-assisted growths show a significant increase in the amount of nitride in the titanium nitride layer at and near the titanium nitride/dielectric interface. Moreover, the amount of chemical binding between the titanium nitride and dielectric is increased when low-energy ions are used. Finally, by using angle resolved x-ray photoemission it was determined that the enhancement in the deposition process from low-energy ions occurs without inducing significant intermixing between the titanium nitride layer and the dielectric. © 2000 American Vacuum Society.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.35.Ct Interface structure and roughness
79.60.Jv Interfaces; heterostructures; nanostructures

Effect of a thin Ni layer on hydrogenation and thermal release characteristics of Ti thin films

L. Q. Shi, Z. Y. Zhou, and G. Q. Zhao

J. Vac. Sci. Technol. A 18, 2262 (2000); http://dx.doi.org/10.1116/1.1285994 (5 pages) | Cited 4 times

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Carbon and oxygen contamination on the Ti surface strongly influences hydrogen absorption and desorption, and it can even passivate the surface completely. The effect of C and O on the hydrogen absorption and thermal release on Ti films was investigated by using high-energy non-Rutherford backscattering and elastic recoil detection techniques. The experimental results show that the concentration gradient in the region of about 300 nm near the surface is very large due to the joint contamination of about 1.26×1016 atoms/cm2 of C and 2.5×1016 atoms/cm2 of O; also, the thermal releasing temperature increased greatly. A thin Ni film coated on the Ti film may considerably reduce the contamination of gaseous impurities, in particular C, and prevents further oxidation and improve the absorption and desorption of hydrogen. © 2000 American Vacuum Society.
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84.60.-h Direct energy conversion and storage
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.35.Dv Composition, segregation; defects and impurities
81.65.Rv Passivation
81.05.Bx Metals, semimetals, and alloys

Damage in diamond produced by analysis beam

Z. Q. Ma, B. X. Liu, and H. Naramoto

J. Vac. Sci. Technol. A 18, 2267 (2000); http://dx.doi.org/10.1116/1.1288941 (4 pages) | Cited 1 time

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The lattice damage of a diamond crystal, caused by the analysis beam of helium ions with 2.0 MeV, 3 nA at room temperature, was characterized by nondestructive optical absorption topographic imaging that used position-sensitive scanning spectroscopy in the transmission mode. The result showed that the atomic structure and electronic states in diamond have been significantly changed by the ion beam, even at very low dose or dose rate. The measurement has been applied to the artificial diamond crystal (type Ib) to evaluate how the damage induced by Rutherford backscattering/channeling, and the comparison to ion implantation (H2+) is given. We found that a high column image, which reflects the defective states in irradiated synthetic diamond, provides a qualitative estimation of damage. © 2000 American Vacuum Society.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
82.80.-d Chemical analysis and related physical methods of analysis

Damage of InP (110) induced by low energy Ar+ and He+ bombardment

Q. Zhao, Z. W. Deng, R. W. M. Kwok, and W. M. Lau

J. Vac. Sci. Technol. A 18, 2271 (2000); http://dx.doi.org/10.1116/1.1286103 (6 pages) | Cited 4 times

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Plasma-induced surface damage of a III–V compound semiconductor, a problem associated with many device fabrication processes, is clarified with careful measurements of surface defect density induced by low energy ion bombardment of InP. In the study, n- and p-InP (110) surfaces were prepared by cleavage of InP in ultrahigh vacuum, and then bombarded as a function of ion type (He+ and Ar+), energy (5–100 eV), and fluence (1012–1017 ions/cm2). The dynamic process of surface Fermi level shifting induced by such bombardment was determined by in situ high-resolution x-ray photoelectron spectroscopy, and the data were then converted to information on surface defect formation. It was found that both He+ and Ar+ bombardment with the above conditions moved the Fermi levels of both n- and p-InP (110) surfaces towards 0.95 eV above the valence band maximum of InP. As expected, for the same bombardment energy, Ar+ caused more damage than He+, and for the same ion type, the bombardment induced a surface defect density increasing with both ion energy and fluence. It was also found that the threshold condition for defect formation was a combined function of the impact energy of the incoming ion and the energy released during its neutralization. © 2000 American Vacuum Society.
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81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Effects of increasing nitrogen concentration on the structure of carbon nitride films deposited by ion beam assisted deposition

P. Hammer, N. M. Victoria, and F. Alvarez

J. Vac. Sci. Technol. A 18, 2277 (2000); http://dx.doi.org/10.1116/1.1285993 (11 pages) | Cited 20 times

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Amorphous carbon nitride films containing increasing concentrations of nitrogen were deposited by ion beam assisted deposition at a substrate temperature of 150 °C. The relationship between the deposition conditions and the chemical bonding structure was investigated by x-ray photoelectron, ultraviolet photoelectron, infrared, and Raman spectroscopies. Film properties were examined by ultraviolet–vis spectroscopy, conductivity, hardness, density, and internal stress measurements. The experimental results confirm a pronounced change of the structure and properties at a nitrogen concentration of about 20 at. %. After reaching a maximum at this concentration, properties like hardness, conductivity, and density show a strong decrease up to a nitrogen content of 35 at. %. In order to identify the formed microstructure and better understand the cause of the structural transformation a statistical model is introduced and the results are compared with the intensities of the deconvoluted spectral features obtained by photoelectron spectroscopy. On the basis of the obtained correlation between independent experiments it is demonstrated that below 20 at. % N an increasing number of nonaromatic CN bonds is formed inducing a localization of nitrogen lone pair electrons and thus stressing the former planar aromatic structures. The addition of more N causes a further reduction of aromatic configurations and a relaxation of the strained network due to the formation of isocyanide structures (C�N–), aliphatic CN bonds, and terminating nitrile groups (–C�N). The nitrogen induced rearrangement of the bonding structure accounts for the lower intrinsic stress values and higher optical gap of these films. Structural information from both Raman and infrared spectra support these findings. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Jj Ion and electron beam-assisted deposition; ion plating
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
62.20.Qp Friction, tribology, and hardness
73.61.Le Other inorganic semiconductors

Vacuum beam studies of photoresist etching kinetics

Frank Greer, J. W. Coburn, and David B. Graves

J. Vac. Sci. Technol. A 18, 2288 (2000); http://dx.doi.org/10.1116/1.1287721 (7 pages) | Cited 13 times

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One factor limiting the development of reliable models of high density, low pressure oxide etch plasmas is the relatively poor understanding of the plasma-photoresist surface interactions. In particular, the relatively high rates of photoresist (PR) loss experienced in high density fluorocarbon plasmas is a significant problem. It has long been accepted that fluorine plays a key role in controlling the oxide to PR etch rate selectivity. The addition of hydrogen has been shown to improve this selectivity, presumably by scavenging fluorine from the tool by forming HF. By reducing the fluorine to carbon ratio in the plasma and more specifically at the PR surface itself, the rate of polymer deposition increases causing the net PR etch rate to decrease. In this work, the complex surface chemistry of fluorocarbon plasmas is simplified to facilitate the study of the interaction of fluorine atoms and hydrogen atoms on the PR surface. This chemistry is modeled in vacuum beam experiments with argon ions and independent fluxes of neutral deuterium and fluorine atoms intersecting at the surface of photoresist samples. We present experimental evidence that the etch yield of photoresist (carbon atoms removed per incident argon ion) under these conditions is high compared to that of silicon and silicon dioxide. The presence of a simultaneous flux of deuterium atoms on the photoresist surface does not affect the etch yield despite the fact that DF is formed during the etching process. © 2000 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.20.Wt Computational modeling; simulation

ZnO:Zn phosphor thin films prepared by ion beam sputtering

W. Li, D. S. Mao, F. M. Zhang, X. Wang, X. H. Liu, S. C. Zou, Y. K. Zhu, Q. Li, and J. F. Xu

J. Vac. Sci. Technol. A 18, 2295 (2000); http://dx.doi.org/10.1116/1.1289694 (7 pages) | Cited 4 times

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ZnO:Zn phosphor thin films used in field emission displays were prepared by ion beam sputtering. Postdeposition annealing of these films was performed at temperatures ranged from 100–1000 °C in N2 atmosphere. Several techniques, including Rutherford backscattering spectroscopy (RBS), x-ray diffraction, atomic force microscopy, Hall effect measurement, and photoluminescence spectra, were employed to characterize these films. RBS results showed there was an amount of excess Zn in the films. The as-deposited films were found to contain both amorphous and crystalline phases. The morphology of the films consisted of several structures. It was detected that the free carrier concentration of these films decreased by increasing annealing temperature, indicating the elimination of excess Zn. Meanwhile, the Hall mobility increased quickly if the annealing temperature exceeded 400 °C, showing the improved crystallinity. Two categories of photoluminescent peaks, ultraviolet/violet and blue/green, were detected in ZnO:Zn films. The singly ionized oxygen vacancies were responsible for the visible luminescence which was strongly affected by the annealing processes. The possible reasons may include recovery of structural defects, homogenization of the films, and evaporation of the excess Zn with different contributions at different temperature ranges. © 2000 American Vacuum Society.
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78.66.Hf II-VI semiconductors
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.72.J- Point defects and defect clusters
61.66.Bi Elemental solids
61.66.Dk Alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
85.45.Fd Field emission displays (FEDs)
81.15.Cd Deposition by sputtering

Characterization studies of diamond-like carbon films grown using a saddle-field fast-atom-beam source

D. Sarangi, O. S. Panwar, S. Kumar, and R. Bhattacharyya

J. Vac. Sci. Technol. A 18, 2302 (2000); http://dx.doi.org/10.1116/1.1289699 (10 pages) | Cited 3 times

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In this article, we report results of an extensive characterization study involving scanning electron microscopy, spectroscopic ellipsometry (SE), photothermal deflection spectroscopy (PDS), x-ray photoelectron spectroscopy, x-ray Auger electron spectroscopy (XAES), current–voltage (I–V) measurements, hydrogen content evaluated from Fourier transform infrared spectroscopy and elastic recoil detection analysis, and also measurement of stress and hardness of diamond-like carbon (DLC) films. These films were grown using methane (CH4), acetylene (C2H2) gases, and benzene (C6H6) vapors into a saddle-field fast-atom-beam (FAB) source. DLC films formed by the saddle-field FAB source technique exhibit extremely low residual stress (0.12–0.26 GPa) and high Knoop hardness (9–22 GPa) measured at 50 g load. The values of optical constants (n, k, ϵ1, ϵ2) evaluated from SE, characteristic energy of band tail (Urbach energy, E0) evaluated from PDS studies, sp2 percentage evaluated from XAES data, the density of states [N(EF)] derived from space-charge-limited conduction, and the hydrogen content are found to decrease, and the sp3/sp2 ratio evaluated are found to increase with the increase of carbon-to-hydrogen ratio in the hydrocarbon gases/vapors used for growing DLC films by this technique. The values of E0, N(EF), hydrogen content, and sp3/sp2 ratio of these DLC films are found to be in the range of 180–280 meV, 1–6×1017 eV−1 cm−3, 3–8 at. % and 5.2–12.3, respectively, which are lower than the values of E0 (300–500 meV), N(EF) (∼1018 eV−1 cm−3), and hydrogen content (15–40 at. %) and higher than sp3/sp2 ratio (1.3–2.5) of DLC films grown by the more conventional rf self-bias technique reported in the literature. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
78.66.Db Elemental semiconductors and insulators
68.35.Gy Mechanical properties; surface strains
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ti, TiN, and Ti/TiN thin films prepared by ion beam assisted deposition as diffusion barriers between Cu and Si

Haicuan Mu, Yuehui Yu, E. Z. Luo, B. Sundaravel, S. P. Wong, and I. H. Wilson

J. Vac. Sci. Technol. A 18, 2312 (2000); http://dx.doi.org/10.1116/1.1288942 (7 pages) | Cited 4 times

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A comparative study of Ti and TiN [ion beam assisted deposition (IBAD)] films as diffusion barriers for Cu has been done. It is found that amorphous Ti (a-Ti) and TiN (a-TiN) films show better thermal stability than (010) oriented Ti (c-Ti) and (111) oriented TiN (c-TiN) films. Such thermal stability can be attributed to their microstructure lacking grains that are fast diffusion paths compared to the imperfect preferentially oriented films prepared by IBAD. Compared to a 300 Å amorphous TiN layer, a 600 Å c-Ti/a-TiN multilayer shows inferior thermal stability, while improvement resulting from the 600 Å a-Ti/a-TiN multilayer is observed. Reasons for these effects are discussed. © 2000 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Sz Deposition technology
68.35.Fx Diffusion; interface formation
68.60.Dv Thermal stability; thermal effects
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Interaction of alcohols with a-CHx films

Nisha Shukla and Andrew J. Gellman

J. Vac. Sci. Technol. A 18, 2319 (2000); http://dx.doi.org/10.1116/1.1287149 (8 pages) | Cited 3 times

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Temperature programed desorption has been used to study the desorption kinetics and desorption energies of a set of alcohols and fluorinated alcohols adsorbed on an a-CHx film. The alcohols serve as models for the hydroxyl end groups of Fomblin Zdol, the lubricant most commonly used with the amorphous carbon overcoats sputtered onto the surfaces of magnetic data storage disks. Temperature programed desorption has been used to measure the desorption energies of the alcohols over a range of coverages and to compare the desorption energies of fluorinated and hydrocarbon alcohols. The desorption energies are all coverage dependent and decrease with increasing alcohol coverage. This is believed to be due to heterogeneity of the a-CHx films surface. In all cases the low coverage desorption energies of the fluorinated alcohols were found to be higher than those of their hydrocarbon counterparts. The implications of this observation are that the interaction of the alcohols is through hydrogen bonding of the hydroxyl groups to the a-CHx films. This conclusion is consistent with that reached in a similar study of the adsorption of alcohols to the surfaces of a-CNx films. © 2000 American Vacuum Society.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.40.Pq Friction, lubrication, and wear

Fabrication of ZnO-doped Zr0.8Sn0.2TiO4 thin films by radio frequency magnetron sputtering

Cheng-Liang Huang and Cheng-Shing Hsu

J. Vac. Sci. Technol. A 18, 2327 (2000); http://dx.doi.org/10.1116/1.1286143 (6 pages) | Cited 3 times

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(Zr0.8Sn0.2)TiO4 (ZST) thin films with 1 wt % ZnO addition were fabricated on n-type (100) Si substrates by reactive rf magnetron sputtering at various Ar/O2 mixing ratios (80/20, 90/10), substrate temperatures (300, 350, and 400 °C), and sputtering times (from 2–4 h). The powder target composition of (Zr0.8Sn0.2)TiO4 was synthesized in the experiment. The structure of the films on Si was determined by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The deposition rate increases with increasing Ar concentration and substrate temperature. Moreover, the higher O2 content increases the surface roughness of the deposited films. From observing the cross section and the surface morphology, ZST thin films exhibit a columnar structure. The grain size of the film increased with an increase in the substrate temperature and sputtering time and with a decrease in the oxygen partial pressure. A dielectric constant of 28 (f=10 MHz) and a resistivity of 2.1×109 Ω m were obtained for the ZST thin films in the experiment. © 2000 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.35.B- Structure of clean surfaces (and surface reconstruction)
77.22.Ch Permittivity (dielectric function)
73.61.Ng Insulators
77.55.-g Dielectric thin films

Low-temperature magnetron sputter-deposition, hardness, and electrical resistivity of amorphous and crystalline alumina thin films

Quan Li, Yuan-Hsin Yu, C. Singh Bhatia, L. D. Marks, S. C. Lee, and Y. W. Chung

J. Vac. Sci. Technol. A 18, 2333 (2000); http://dx.doi.org/10.1116/1.1286715 (6 pages) | Cited 20 times

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Aluminum oxide films were grown by reactive magnetron sputtering. In order to maintain a stable deposition process and high deposition rate, a pulsed direct current bias was applied to the aluminum target and the substrate. An external solenoid was used to form a magnetic trap between the target and the substrate. The influence of substrate temperature, substrate bias, and the magnetic trap on film growth and properties was studied by different surface and thin-film analysis techniques and electrical measurements. Normally, amorphous alumina films were produced. However, under optimum process conditions, crystalline alumina films can be obtained at temperatures as low as 250 °C, with a hardness ∼20 GPa and excellent electrical insulating properties. © 2000 American Vacuum Society.
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81.15.Cd Deposition by sputtering
73.61.Ng Insulators
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
72.80.Sk Insulators
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance

Epitaxial growth and physical properties of Permalloy film deposited on MgO(001) by biased dc plasma sputtering

Masaki Ishino, Jiping Yang, Kenji Makihara, Ji Shi, and Mituru Hashimoto

J. Vac. Sci. Technol. A 18, 2339 (2000); http://dx.doi.org/10.1116/1.1286200 (5 pages) | Cited 3 times

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Permalloy films 5 to about 40 nm thick were deposited on MgO(001) substrates at 230 °C by biased dc plasma sputtering at 2.7 kV in pure Ar gas using a Ni0.77Fe0.23 target. A bias voltage Vs between 0 and −150 V was applied to the substrate during deposition. The initial growth structure and physical properties of epitaxial films were investigated by x-ray photoelectron spectroscopy, reflection high energy electron diffraction, transmission electron microscopy, and by measuring electrical and magnetic properties. Epitaxial FCC–Ni1−xFex (Permalloy) films, where x is scattered between 0.36 and 0.32, could be prepared with NiFe(001)[010]∥MgO(001)[010] in full thickness independently of Vs. However, films with lower electrical resistivity and with higher saturation magnetization having an atomically smooth surface could be prepared at Vs=−90 V. The film was composed of discrete islands of at least 5 nm thickness at an initial growth stage. Misfit dislocations were already formed even in isolated islands along the MgO 100 direction with lattice expansion along the same direction. The practical lattice misfit f computed from transmission electron diffraction patterns gradually increased reaching the theoretical value with an increase in thickness up to 17 nm. Such an f dependence on thickness could be reasonably simulated on the basis of van der Merwe’s model. Thus the epitaxial Permalloy film grows forming misfit dislocations as well as expanding the lattice at the MgO interface to keep a balance between the energies of strain and dislocation. Under the application of Vs, the initial discrete island structure on the MgO substrate might be modified not only by accelerated incoming ions but also by charged ions on the insulating substrate. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Amorphous carbon films deposited by direct current-magnetron sputtering: Void distribution investigated by gas effusion and small angle x-ray scattering experiments

F. L. Freire, L. G. Jacobsohn, D. F. Franceschini, and S. S. Camargo

J. Vac. Sci. Technol. A 18, 2344 (2000); http://dx.doi.org/10.1116/1.1289696 (5 pages) | Cited 5 times

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Amorphous carbon films were deposited by direct current-magnetron sputtering onto p-doped (100) silicon crystals and onto ultrapure aluminum foils at different argon pressures, ranging from 0.17 to 1.4 Pa. The film density was determined by the combination of the areal density, obtained from ion beam analysis, and the film thickness measured by a stylus profilometer. Film density decreased when the argon pressure used during deposition was increased. Gas effusion measurements indicated that the films deposited at low pressures are more compact than the films deposited at higher pressures. In the case of the latter, C2Hn effusion at temperatures as low as 250 °C indicated that they have an open structure that allows the evolution of large molecules. Small angle x-ray scattering results revealed an increase of the void density with increasing plasma pressure. Guinier plots show that these voids have a broad distribution of sizes, ranged from 7 to 26 Å, which is nearly independent of the plasma pressure. A direct correlation between film density and the open volume fraction in the films was found. These different film microstructures could be explained by the existence of different bombardment regimes during film growth: films deposited at lower plasma pressures are hard and dense, while soft films grown at higher pressures have an open microstructure. © 2000 American Vacuum Society.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Cd Deposition by sputtering
61.43.Er Other amorphous solids
61.05.cf X-ray scattering (including small-angle scattering)

Growth, structure, and mechanical properties of CNxHy films deposited by dc magnetron sputtering in N2/Ar/H2 discharges

Niklas Hellgren, Mats P. Johansson, Björgvin Hjörvarsson, Esteban Broitman, Mattias Östblom, Bo Liedberg, Lars Hultman, and Jan-Eric Sundgren

J. Vac. Sci. Technol. A 18, 2349 (2000); http://dx.doi.org/10.1116/1.1286395 (10 pages) | Cited 25 times

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Hydrogenated carbon nitride films were deposited by reactive dc magnetron sputtering in mixed Ar/N2/H2 discharges at temperatures of 100 and 350 °C. The total pressure was kept constant at 0.33 Pa and the gas mixtures were varied in order to study the effect of the hydrogen on the resulting film structure and properties. Chemical sputtering effects taking place during deposition were found to be an important factor for the growth and structural evolution. When H2 is mixed into the discharge gas, the growth rate decreases considerably and the films become denser due to desorption of volatile species, like hydrocarbons, NH3 and HCN. For a H2 fraction above 15%, no net film growth takes place. The hydrogen concentration incorporated into the films was highest (up to ∼33 at. %) for low growth temperatures and low nitrogen concentrations. Furthermore, the results indicate that substantial amount of hydrogen are bonded to nitrogen. The incorporation of hydrogen in the structure interrupts the relatively long basal planes in graphite-like structures, and some regions transform into an amorphous structure. Nanoindentation measurements of the film showed decreased elasticity, as well as decreased hardness when incorporating hydrogen. However, fullerene-like films grown at 350 °C in N2/H2 discharges exhibit high elasticity for H2 partial pressures as high as ∼10−3 Pa due to low H incorporation into these films. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.66.Fn Inorganic compounds

Chemical structure change of thin films prepared from nonpolymeric organic compounds by pulsed laser deposition

Takahiro Kajitani, Osamu Tanaka, Yoshihiro Tange, Hideaki Matsuda, Toshihiko Ooie, Tetsuo Yano, Masafumi Yoneda, Munehide Katsumura, and Yoshifumi Suzaki

J. Vac. Sci. Technol. A 18, 2359 (2000); http://dx.doi.org/10.1116/1.1289695 (4 pages)

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Thin films from six kinds of nonlinear optical nonpolymeric organic compounds were prepared by pulsed laser deposition (PLD) using a KrF excimer laser (248 nm) at various fluences up to 50 mJ/cm2. Changes in the chemical structure of the films with changes in fluence were studied. The experimental results show that for every compound at least minor decomposition has already started at the threshold fluence for deposition. More serious degradation occurs with increasing fluences, and little of the original chemical structure remains in films prepared by PLD at a fluence of 50 mJ/cm2. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
42.65.-k Nonlinear optics
42.70.Mp Nonlinear optical crystals

Laser-induced photodetachment in high-density low-pressure SF6 magnetoplasmas

L. St-Onge, M. Chaker, and J. Margot

J. Vac. Sci. Technol. A 18, 2363 (2000); http://dx.doi.org/10.1116/1.1285935 (9 pages) | Cited 5 times

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Using laser-induced photodetachment (LIPD), we investigate in some detail how different discharge parameters affect the negative ion fraction in high-density low-pressure SF6 magnetoplasmas sustained by the propagation of electromagnetic surface waves. A plane electrostatic probe is used for collection of the photodetached electrons. Careful testing of the LIPD technique itself is carried out prior to systematic measurements and adequate laser fluence conditions are determined. Negative ions are found to outnumber electrons several times, even at mTorr and submTorr pressures, indicating the important electronegative character of the discharge. The dependence of the negative ion fraction on gas pressure, argon admixture, microwave power, and axial and radial position in the reactor is interpreted on the basis of different negative ion formation and loss mechanisms. The negative ion fraction is found to be maximum in conditions and regions of minimal electron temperature and positive ion density. © 2000 American Vacuum Society.
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33.80.Eh Autoionization, photoionization, and photodetachment
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.30.-q Plasma dynamics and flow
52.25.-b Plasma properties

Evaporation and ion assisted deposition of HfO2 coatings: Some key points for high power laser applications

B. Andre, L. Poupinet, and G. Ravel

J. Vac. Sci. Technol. A 18, 2372 (2000); http://dx.doi.org/10.1116/1.1287153 (6 pages) | Cited 11 times

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Optical interference filters made by layers of optical coatings are used to shape and transport laser beams. If a defect is present in the stack (cosmetic defect, stoichiometry defect, absorption band…), and high laser power density is reached, a strong energy into the material can be deposited involving the destruction of the coatings (either by melting or mechanical failure). One of the key methods to achieve high performance coatings is to reduce such defects as much as possible. Hafnia (HfO2) coatings are undoubtedly one of the most successful materials for high power laser applications. Associated with a low index material such as silica, high laser induced damage threshold (LIDT) interference filters can be achieved. Hafnia is often the LIDT limiting factor. During the evaporation HfO2 particles create buried defects in the deposited material. These defects are sources of the coating damage during laser irradiation. To avoid this phenomenon we have evaporated metallic hafnium that was oxidized by oxygen inlet into the vacuum chamber or use an oxygen ion beam bombardment during the film growth. Argon or, better, xenon ions in the beam produced densities as high as 99% of the bulk, with low water content, and an improved optical transmission in the mid infrared window. This article deals with the optimization of such a deposition process regarding coating density, mechanical stresses, and optical properties (optical absorption). Films deposited by HfO2 evaporation are compared especially using photothermal mapping. The stoichiometry of the defects determined thanks to localized Auger spectroscopy clearly indicates how injurious such defects could be for high laser flux applications. Finally, laser damage thresholds of the films at 1.06 μm are measured and possible damage mechanism discussed. © 2000 American Vacuum Society.
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42.79.Wc Optical coatings
42.79.Ci Filters, zone plates, and polarizers
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.60.Bs Mechanical and acoustical properties
62.20.-x Mechanical properties of solids
79.20.Fv Electron impact: Auger emission
78.30.Hv Other nonmetallic inorganics

Influence of oxygen background pressure on the structure and properties of epitaxial SrTiO3/La0.35Nd0.35Sr0.3MnO3 heterostructures grown by pulsed laser deposition

Wenbin Wu, K. H. Wong, C. L. Mak, Geoffrey Pang, C. L. Choy, and Yuheng Zhang

J. Vac. Sci. Technol. A 18, 2378 (2000); http://dx.doi.org/10.1116/1.1287446 (6 pages) | Cited 2 times

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Epitaxial La0.35Nd0.35Sr0.3MnO3 (LNSMO) films and SrTiO3 (STO)/LNSMO heterostructures have been grown on LaAlO3 substrates by pulsed laser deposition. The effect of oxygen content on structure and properties of both the LNSMO and STO/LNSMO films was investigated through x-ray diffraction, atomic force microscopy, and resistivity-temperature measurements. It is found that the out-of-plane lattice constant and the metallic-semiconducting transition temperature of the LNSMO films are greatly influenced by the oxygen pressure during deposition, but, insensitive to the in situ annealing oxygen pressure ranging from 2×10−6 to 10 Torr after the deposition. For the STO/LNSMO heterostructures, oxygen out-diffusion from the LNSMO layer is evidenced when the top STO is deposited at an oxygen pressure of less than 5×10−4 Torr and temperatures higher than 500 °C. Our results strongly suggest that at the surface of as-grown LNSMO films a native passivation layer for oxygen diffusion may exist, and this layer could be damaged after depositing the STO film at reduced oxygen pressures. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Fg Pulsed laser ablation deposition
71.30.+h Metal-insulator transitions and other electronic transitions
75.70.Ak Magnetic properties of monolayers and thin films
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
66.30.H- Self-diffusion and ionic conduction in nonmetals

The deposition behavior of SiO2–TiO2 thin film by metalorganic chemical vapor deposition method

Si-Moo Lee, Jeong-Hoon Park, Kug-Sun Hong, Woon-Jo Cho, and Dong-Lae Kim

J. Vac. Sci. Technol. A 18, 2384 (2000); http://dx.doi.org/10.1116/1.1287154 (5 pages) | Cited 8 times

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SiO2–TiO2 thin films were deposited by metalorganic chemical vapor deposition using an alkoxide source. At 680 °C, the deposition rate curve showed parabolic behavior and the refractive index increased linearly from 1.45 to 2.35 with increasing titanium tetraisopropoxide: Ti(OC3H7)4(TTIP) ratio. Each oxide component in the film was separated analytically and its effective deposition rate, in the composite thin film, was calculated to analyze the deposition mechanism of the mixed sources. A Lorentz–Lorenz model was used to attain the composition of the film for each component separation. Effective SiO2 deposition from tetraethylorthosilicate: Si(OC2H5)4(TEOS) showed parabolic behavior with increasing TTIP ratio, while the effective TiO2 deposition did not. In addition, TTIP lowered the apparent activation energy of SiO2 deposition significantly from ∼40 to ∼10 Kcal/mol. From this, it was concluded that TTIP enhanced the TEOS decomposition, which results in the anomalous deposition behavior in composite films. A more reactive TTIP molecule acting as a “free radical reaction initiator” was suggested as a mechanism for enhancement of the process. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
68.55.Nq Composition and phase identification
42.79.Wc Optical coatings

Properties of nitrogen doped silicon films deposited by low-pressure chemical vapor deposition from silane and ammonia

P. Temple-Boyer, L. Jalabert, L. Masarotto, J. L. Alay, and J. R. Morante

J. Vac. Sci. Technol. A 18, 2389 (2000); http://dx.doi.org/10.1116/1.1286714 (5 pages) | Cited 18 times

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Nitrogen doped silicon (NIDOS) films have been deposited by low-pressure chemical vapor deposition from silane SiH4 and ammonia NH3 at high temperature (750 °C) and the influences of the NH3/SiH4 gas ratio on the films deposition rate, refractive index, stoichiometry, microstructure, electrical conductivity, and thermomechanical stress are studied. The chemical species derived from silylene SiH2 into the gaseous phase are shown to be responsible for the deposition of NIDOS and/or (silicon rich) silicon nitride. The competition between these two deposition phenomena leads finally to very high deposition rates (≈ 100 nm/min) for low NH3/SiH4 gas ratio (R≈0.1). Moreover, complex variations of NIDOS film properties are evidenced and related to the dual behavior of the nitrogen atom into silicon, either n-type substitutional impurity or insulative intersticial impurity, according to the Si–N atomic bound. Finally, the use of NIDOS deposition for the realization of microelectromechanical systems is investigated. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Cw Elemental semiconductors
73.61.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.J- Point defects and defect clusters
68.55.Nq Composition and phase identification
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.Bs Mechanical and acoustical properties

Comparison of titanium oxide films grown on bare glass and boiled glass in 50% H2SO4 by metal-organic chemical vapor deposition

H. K. Jang, S. W. Whangbo, Y. D. Chung, T. G. Kim, H. B. Kim, I. W. Lyo, C. N. Whang, C. H. Wang, D. J. Choi, T. K. Kim, and H.-S. Lee

J. Vac. Sci. Technol. A 18, 2394 (2000); http://dx.doi.org/10.1116/1.1288137 (6 pages) | Cited 1 time

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Titanium oxide films were deposited on bare glass and boiled glass in 50% H2SO4 for 30 min at various substrate temperatures by metal-organic chemical vapor deposition. We investigated the effects of a substrate temperature between 300 and 550 °C on such properties as thermal stability, deposition rate, and chemical states of the films. The thickness of the films is independent of the substrate treatments. The deposition rate of the films is linearly decreased with increasing substrate temperature. Rutherford backscattering spectroscopy and x-ray photoelectron spectroscopy results indicate that the H2SO4 treated glass substrate is superior to the bare glass substrate in the suppression of out-diffusion of sodium and calcium through the TiO2 film till a substrate temperature of 500 °C. There exist only Ti3+ and Ti4+ oxidation states in the film regardless of a substrate temperature and substrate treatment. Ti3+ fractional composition are changed slightly between 0.11 and 0.17 and Ti4+ fractional composition are changed between 0.82 and 0.90 with varying substrate temperature. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.60.Dv Thermal stability; thermal effects
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Chemical vapor deposition of Ru thin films by direct liquid injection of Ru(OD)3 (OD=octanedionate)

Jung-Hyun Lee, Joo-Young Kim, Shi-Woo Rhee, DooYoung Yang, Dong-Hyun Kim, Cheol-Hoon Yang, Young-Ki Han, and Chul-Ju Hwang

J. Vac. Sci. Technol. A 18, 2400 (2000); http://dx.doi.org/10.1116/1.1289693 (4 pages) | Cited 11 times

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Pure Ru thin films were deposited on Si substrate using Ru (OD)3 (OD = octanedionate) as a new liquid precursor with a newly designed warm wall reactor by metalorganic chemical vapor deposition (MOCVD). Resistivity and film structure were largely dependent on MOCVD process parameters such as deposition temperature, O2/(O2+Ar) ratio, and reactor pressure. With the increase of O2/(O2+Ar) ratio, minimum resistivity (20 μΩ cm) was obtained and then the resistivity was increased due to the abnormal increase of surface roughness. By modifying the position of a single quartz injector, uniform deposition of Ru thin films on an 8 in. Si wafer could be obtained. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.61.At Metal and metallic alloys
81.40.Rs Electrical and magnetic properties related to treatment conditions

Variable angle spectroscopic ellipsometry of fluorocarbon films from hot filament chemical vapor deposition

Kenneth K. S. Lau, Jeffrey A. Caulfield, and Karen K. Gleason

J. Vac. Sci. Technol. A 18, 2404 (2000); http://dx.doi.org/10.1116/1.1288191 (8 pages) | Cited 12 times

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Hot filament chemical vapor deposition using hexafluoropropylene oxide as the precursor gas yielded two sets of fluorocarbon films, one with varying OH/COOH content and the other with varying grain aspect ratio, as revealed by Fourier transform infrared spectroscopy and atomic force microscopy, respectively. Variable angle spectroscopic ellipsometry was performed to derive film thickness and film optical constants. A uniaxial Cauchy–Urbach dispersion layer, with separate in-plane and out-of-plane dispersion parameters, was found to realistically describe the films. Derived film thickness agreed well with profilometry measurements. Anisotropy in index of refraction n and extinction coefficient k was on the order of 10−2 and 10−5 to 10−3, respectively. The relationship between the complex index of refraction and the dielectric function allowed the optical dielectric constant ϵ1 to be calculated. The presence of OH did not affect the film optical dielectric constant significantly. Even though OH/COOH groups are considered to contribute adversely by increasing the dielectric constant, their effect may have been masked by the dominance of F atoms. The optical dielectric constant decreased linearly with increasing grain aspect ratio. The presence of voids was thought to lower the effective index of refraction and optical dielectric constant, and the increase in grain asymmetry created more of these voids due to less efficient packing. By assuming a linear contribution from bulk grains and voids to the effective optical dielectric constant, film porosity was derived. A maximum film porosity of 33%, corresponding to an optical dielectric constant of 1.74, was observed. © 2000 American Vacuum Society.
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78.66.Qn Polymers; organic compounds
42.79.Wc Optical coatings
68.55.-a Thin film structure and morphology
78.30.Jw Organic compounds, polymers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.22.Ch Permittivity (dielectric function)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Effect of oxygen stoichiometry on the ferroelectric property of epitaxial all-oxide La0.7Sr0.3MnO3/Pb(Zr0.52Ti0.48)O3/La0.7Sr0.3MnO3 thin-film capacitors

Wenbin Wu, K. H. Wong, C. L. Mak, C. L. Choy, and Y. H. Zhang

J. Vac. Sci. Technol. A 18, 2412 (2000); http://dx.doi.org/10.1116/1.1288195 (5 pages) | Cited 7 times

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Epitaxial all-oxide ferroelectric thin-film capacitors, La0.7Sr0.3MnO3/Pb(Zr0.52Ti0.48)O3/La0.7Sr0.3MnO3 (LSMO/PZT/LSMO), have been grown on LaAlO3(001) substrates by pulsed-laser deposition. By changing the deposition oxygen pressure, we varied the oxygen content in the oxide electrodes and ferroelectric film, respectively, and studied their effect on switching and fatigue behavior of the epitaxial capacitors. The capacitors were also cooled at various oxygen pressures in the range of 5×10−6–10 Torr to examine their tendency to process-induced imprint. It is found that all the capacitors show almost square hysteresis loops with remnant polarization of 35–40 μC/cm2 and a coercive field of 40–50 kV/cm, irrespective of the oxygen concentration in the ferroelectric and electrode films. Contrary to the capacitors using La0.5Sr0.5CoO3 as electrodes, when cooled at reduced oxygen pressures, the LSMO/PZT/LSMO capacitors show a strong resistance to the process-induced imprint failure, which is ascribed to the high thermal stability of the LSMO films. On the other hand, the oxygen content in the electrodes is shown to be an important factor that controls the fatigue behavior of the epitaxial all-oxide ferroelectric capacitors. © 2000 American Vacuum Society.
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84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.Nq Composition and phase identification
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis
68.60.Dv Thermal stability; thermal effects
77.22.Ej Polarization and depolarization
81.15.Fg Pulsed laser ablation deposition

Preparation and characterization of clean, single-crystalline YHx films (0⩽x⩽2.9) on W(110)

J. Hayoz, Th. Pillo, M. Bovet, A. Züttel, St. Guthrie, G. Pastore, L. Schlapbach, and P. Aebi

J. Vac. Sci. Technol. A 18, 2417 (2000); http://dx.doi.org/10.1116/1.1286073 (15 pages) | Cited 11 times

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