Changes In Deposition Rates Research Articles

Stress reduction in silicon dioxide layers by pulsing an oxygen/silane helicon diffusion plasma

A low pressure, high density helicon reactor used to deposit silicon dioxide (SiO2) from a mixture of oxygen/silane has been pulsed with a constant “on” time of 500 μs and a duty cycle varying from 10% to 100%. Over this range, the deposition rate changes by only a factor of 2.5 implying that deposition is continuing in the postdischarge with a time constant of 1 ms. For duty cycles of 30% and above, the films show good characteristics but the 10% duty cycle has a somewhat higher “p etch” implying some porosity. The pulsing reduces the compressive stress by at least a factor of two. This is correlated with the reduction in the measured plasma potential and density implying that for the present conditions, the stress is determined by the energy and number of ions striking the growing film. For the low ion energies considered here (⩽50 eV) a simple model using a temporal evolution of the ion energies and fluxes measured in an argon plasma suggests that the compressive stress would decrease in the postdischarge with a time constant of about 80 μs, assuming that the total stress is the integral of the stress over the on and “off” periods. The experimental results in oxygen/silane plasmas show that this is probably an upper limit and the actual decay time may be considerably less.

Influence of the substrate temperature on silicon–carbon thin films deposited from SiH 4 and C 2H 4 by excimer lamp–CVD

Amorphous hydrogenated silicon–carbon layers have been prepared on silicon and aluminium substrates by photo-chemical vapour deposition from silane and ethylene by using a Xe 2 * excimer lamp. Films produced at different substrate temperatures have been systematically characterised by ellipsometry, Fourier Transform Infrared Spectroscopy (FTIR), profilometry, Raman Spectroscopy and Energy Dispersive X-ray Spectroscopy (EDS). Ellipsometric studies reveal that the refractive index rises linearly from 1.5 to 2.3 and the deposition rate changes significantly when the substrate temperature is increased. Moreover, EDS analysis indicates an enhancement of the silicon to carbon ratio. Homonuclear silicon and carbon bonds are observed in the Raman spectra, and infrared spectroscopy shows hydrogen incorporated in the films bonded to both silicon and carbon atoms. An atypical increase of the amount of Si–H and a shift of its stretching frequency is found for increasing temperatures. Spontaneous effusion of hydrogen bonded to silicon and a consequent incorporation of oxygen in these vacancies, which provokes a diminution of the refractive index and a shift of the Si–H stretching frequency to higher values, is observed during film aging.

Time dependence and spatial distribution of the deposition rate of YBa2Cu3O7 thin films in 90° off-axis sputtering

We have examined the time dependence and spatial distribution of the deposition rate of YBa2Cu3O7 (YBCO) thin films in 90° off-axis radio frequency planar magnetron sputtering throughout the life of a target. We have found that although the amount of YBCO sputtered from the target is constant, the amount of YBCO deposited on the substrate decreases linearly over time. Furthermore, the time dependence of the deposition rate changes at different positions on the substrate. The changes in the deposition rate at any point along the substrate as a function of time can be explained by the change in the angular distribution of the sputtered particles that is caused by changes in the target erosion groove geometry, and the decrease in the kinetic energy of sputtered particles that is indicated by the decrease in the self-bias voltage over time.

Stratal patterns in the southwestern margin of the Ulleung Basin off southeast Korea: sequence architecture controlled by back-arc tectonism

Major variations in type and rate of tectonic movement in the southwestern margin of the Ulleung Basin coincide in time with changes in stratal patterns at succession boundaries, suggesting that the effect of tectonism was dominant for the development of sequence architecture. During the back-arc opening (16–12 Ma), the rise of relative sea level and the high rate of sediment supply gave rise to sequences with sigmoid progradational patterns. During the back-arc closing (12–6.5 Ma), fall- and rise-dominated relative sea-level fluctuations resulted in sequences with varying stratal patterns depending upon changes in deposition rate. The rise-dominated relative sea level has been prevalent during the later stage (6.5 Ma–Present) with low sedimentation rate.

Changing Contributions of Suspended Sediment Sources in Small Basins Resulting from European Settlement on the Canadian Prairies

Lake sediments provide an integrated record of the sediment yields and sources in the contributing basin. In the research area on the prairies of western Canada, the earliest sediments deposited in the larger lakes predate European settlement, allowing direct evaluation of basin response to settlement. Lake sediment cores were collected from an unnamed lake in the Stony Creek drainage basin in the aspen parkland region of eastern Saskatchewan. Pre- and post-settlement sediments in a central core were separated on the basis of an increase in Populus pollen associated with the southward advance of the aspen parkland ecotone caused by fire suppression following settlement. A wet chemical extraction procedure was used to separate the operationally defined organic fraction, the acid-soluble authigenic fraction, and biogenic silica from the clastic, non-carbonate, allogenic fraction of the lake sediment. Changes in the mineralogy and geochemistry of the clastic, allogenic fraction indicate that settlement resulted in an increased contribution of topsoil to the sediment load of Stony Creek. Elemental ratios, however, show that topsoil did contribute to the allogenic lake sediment fraction prior to settlement. Post-settlement changes in deposition rates of the allogenic fraction resulted from changes in land use rather than from climatic variability. Allogenic deposition rates reached a maximum in the 1950s and 1960s owing to an increase in the area under field crops and the increased use of high-powered agricultural machinery. Allogenic deposition rates decreased in more recent years because of a more extensive application of soil conservation measures. Post-settlement changes in deposition rates of individual elements within the allogenic fraction indicate that various sediment sources respond differently to changes in land use. Over the most recent 100 years, since the onset of European settlement, the erosional response of the basin appears to be controlled by land use changes rather than by climatic variability. © 1997 John Wiley & Sons, Ltd.

Extensional Fault-Bend Folding and Synrift Deposition: An Example from the Central Sumatra Basin, Indonesia

We describe an analytical method for interpreting the geometry and structural history of asymmetric half grabens in rift basins with extensional fault-bend fold theory. Using seismic reflection profiles from the Central Sumatra basin and balanced forward models, we show how local variations in tectonic subsidence relative to deposition rates yield distinctive patterns of folded synrift strata and unconformities that record basin history. If the deposition rate exceeds the local subsidence rate, folded growth strata form upwardly narrowing kink bands that have been described previously as growth triangles. In contrast, if the deposition rate is less than or equals the local subsidence rate, growth strata are folded and truncated at the surface on half-graben margins. Subsequent increases in deposition rate relative to subsidence rate form angular unconformities near the half-graben margins. These unconformities develop without the necessity of erosion and are folded by continuing fault slip. Strata above and below the unconformities are concordant in the deeper parts of the half grabens. Thus, angular unconformities on half-graben margins are helpful for defining sequence boundaries that may reflect changes in deposition and tectonic subsidence rates. In addition, fault-bend fold interpretations yield fault geometry and measures of horizontal extension, both of which control three-dimensional half-graben geometry ©Copyright 1997. The American Association of Petroleum Geologists. All rights reserved.1Manuscript received April 4, 1995; revised manuscript received June 4, 1996; final acceptance October 23, 1996. 2Texaco Exploration and Production Technology Dept., 3901 Briarpark, Houston, Texas 77042. 3PT CALTEX Pacific Indonesia, Rumbai, Pekanbaru 28271, Indonesia. We thank Hongbin Xiao and John Suppe for helpful insights into their extensional fault-bend fold theory, which provided the foundation for this work. Exceptional reviews by M. Scott Wilkerson and Walter F. Dula, Jr., improved the manuscript. In addition, discussions with Karsani Aulia, Richard E. Bischke, Peter A. Brennan, Chris D. Connors, Paul W. Genovese, Tom L. Heidrick, and Elizabeth A. Lorenzetti provided insights into our structural interpretations and presentation of the theory. Seismic reflection data were provided by PT CALTEX Pacific Indonesia.

Low Temperature Deposition of (Ba, Sr)TiO3 Films by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition

(Ba, Sr)TiO3 films deposited by electron cyclotron resonance plasma chemical vapor deposition at 450° C and 500° C are investigated. The crystallinity, evaluated by X-ray diffraction and by measuring grain size, and electrical properties of films were evaluated for changes in deposition temperature, deposition rate, and Ba content, without a post-deposition annealing. Slower deposition rates as well as higher deposition temperatures were found to improve film crystallinity. Evaluation of electrical properties and film crystallinity revealed that the optimum Ba content of a film deposited at 500° C was 0.4. A 27 nm thick film deposited on a Pt substrate at 500° C and at 1.1 nm/min with a Ba content of 0.4 exhibited a SiO2 equivalent thickness of 0.65 nm and a leakage current density of 4.6×10-7 A/cm2 at 1 V. The film composition was found to be sufficiently uniform throughout, i.e., from the top to the side of the films on a stacked bottom electrode.

Inertial effects on thermophoretic transport of small particles to walls with streamwise curvature—I. Theory

We study the combined action of particle inertia and thermophoresis in boundary layer aerosol flows over surfaces with streamwise curvature, in the limit of small particle Stokes number, Stk, when the interaction between these two transport mechanisms is expected to be most significant. The governing dimensionless parameter controlling inertial effects is found to be Stk • Re x 1 2 , which can be large enough to cause dramatic changes in deposition rates even when Stk ⪡ 1, due to the largeness of the streamwise Reynolds number, Re x in boundary layer flows. Predictions are presented for concave/convex surfaces either ‘colder’ or ‘hotter’ than the mainstream.

The effect of deposition rate and sample thickness on the luminescence emitted by electron irradiated polycrystalline H 2O ice

The luminescence arising from the excitation by 0.53 MeV electrons of vacuum deposited polycrystalline ice at 77 K, has been studied as a function of deposition rate and ice thickness. Changes in deposition rate from 0.03 to 17 mm h −1, at various constant sample thicknesses, affected the luminescence intensity, I, but did not significantly affect the decay half-life, nor C in the equation I = A + B(1 − C n ) for the dependence of light intensity, I, on the number of electron pulses, n. Increases in ice thickness from 0.25 μm to 5 mm caused: (i) an increase in luminescence intensity to a plateau value at a thickness around 2 mm; (ii) a blue-shift in the spectral maximum from 405 to 385 nm; and (iii) an increase in the decay half-life from 90 to 160 ns.

Investigation on RF styrene plasma by emission spectroscopy

In order to gain an insight into the processes in an RF styrene plasma, gas phase plasmas were investigated by emission spectroscopy. The plasma reactor was a bell-jar-type chamber with two parallel plate electrodes. The measurement of plasma emission spectra was made with axial resolution. The correlations among the emission intensities of CH and C/sub 4/H/sub 2//sup +/ species, the polymer deposition rate and the polymeric structure of the deposited films were studied. The proposed analysis showed that the gas flow pattern in the plasma reactor, and the difference in collisions between styrene monomer molecules and energetic free electrons occurring in the plasma region and RF sheath, made the fragments and ions produced change in the different regions, resulting in a change in polymeric structure and deposition rate of the polymer films. With increasing distance between the substrate position and the lower electrode, the deposition rate and the concentration of phenyl groups both at the polymer surface and in the bulk decreased.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Kinetic model for scanning laser-induced deposition from the liquid phase

The effect of precursor concentration (0.005–0.05M) and scanning speed (0.20–0.96 mm/s) on the volume of the deposited material, determined with a circumstantial procedure using the cross-sectional data measured by a DEKTAK profilometer, in pyrolytic laser writing from aqueous solutions of ammonium heptamolybdate has been studied. From the detailed investigation we have given evidences that the structures of the deposits and their concentration and scanning speed dependencies can be consequently interpreted on the basis of material supply speeds, i.e. short illumination times, minutes deposition rates are observed indicating that material transport takes place via short-range diffusion. On decreasing the writing speed, i.e. increasing the dwell time, the slope of the volume versus dwell time function is higher because of forced (convectional) material supply due to local stirring in the liquid phase in close proximity to the heated surface area. With a further increase of the dwell time a saturation effect was also observed due to material depletion from the vortex affected liquid volume which can only be eliminated by less effective long-range diffusion. The main result of this work is a semi-quantitative description of the kinetics of the deposition process which gives an explanation for the large variety of morphologies and changes in deposition rates in terms of material transport.

Properties of silicon nitride films prepared by magnetron sputtering

Numerous silicon nitride films were prepared using different target materials (Si3N4 or Si) and different discharge gases (Ar or N2). In the case with an Si4N4 target and Ar gas pressure (1 Pa), the N-to-Si atomic ratio of the film was stoichiometric, 1.33, even when the substrate temperature was changed considerably. When the As gas pressure was increased from 1 7 Pa, the nitrogen content increased while the deposition rate decreased. In the case with an Si3N4 or Si target and N2 gas, the nitrogen content increased while the deposition rate decreased with the increase in N2 pressure. The change in deposition rate due to the pressure was investigated using optical emission spectroscopy.X-ray photoelectron spectroscopy analysis showed that the binding energy is the same if the N-to-Si ratio was in the range from 1.33 to 1.70. It was found by X-ray diffraction analysis that crystallization occured when the substrate temperature was higher than about 1173 K.

Metal overlayers on self-organized molecular assemblies. IV. Ion scattering spectroscopy of the Ag/CH3 interface

Ion scattering spectroscopy (ISS) of vacuum deposited Ag on octadecanethiol (ODT, HS(CH2)17CH3) organized molecular assemblies (OMAs) provides a means of studying interfacial structure at metal/organic interfaces under controlled conditions. The OMAs were self-assembled onto gold films on silicon 〈100〉 substrates. ISS compositional depth profiles of the Ag/CH3 interface were performed at a number of temperatures between 113 and 293 K. Results from these experiments show clearly that Ag penetrates rapidly through ODT above ∼200 K. The changes in ISS Ag peak intensities as a function of time and temperature provide evidence for the formation of Ag clusters at the ODT/Au interface after penetration of Ag. Changes in deposition rate between 0.003 and 0.015 nm/s yielded little difference in corresponding ISS depth profiles. Over a range of ion beam current densities from 0.06 to 2.0 μA/cm2, scaled compositional depth profiles were found to be comparable within experimental error.

Properties of titanium and aluminum thin films deposited by collimated sputtering

A study of the properties of titanium and aluminum films deposited by collimated sputtering is presented. The effect of square grid collimators on the film coverage and film bulk properties has been studied experimentally and theoretically using a Monte Carlo vapor transport simulation, SIMSPUD. The computer simulation is able to model the effect of collimation on the angular distributions of deposited atoms and predict the film coverage and deposition rate changes for both titanium and aluminum. In good agreement with these predictions, experimental films show that bottom coverage in trenches of aspect ratio (depth:width) 1.2 can be significantly improved from 50% to more than 80% for a titanium film, and from 35% to more than 82% for an aluminum film with a collimator of aspect ratio 2. As a further consequence of collimation, the microstructure and film properties are altered in comparison with conventional films. For example, free-standing micro-beam experiments and X-ray diffraction spectra both show a substantial increase in compressive stress in Ti films deposited using collimation. In addition, collimation slightly alters the grain orientation distribution in Ti films, although pressure has a much more important role in determining microcrystallinity. Most of these collimation effects can be explained in terms of changes in the angular distributions, deposition rates and peening.

Experimental study and computer simulation of collimated sputtering of titanium thin films over topographical features

An experimental study and computer simulation of collimated sputtering of titanium (Ti) thin films onto submicrometer trenches is presented. The effect of square grid collimators with aspect ratios varying from 0.5 to 2 has been studied. Simulation of collimated sputtering involves the combination of the simulation of sputter distributions vapor transport model and the simulation by ballistic deposition film growth model. This combination is able to simulate the effect of collimation on the spatial and angular distributions of deposited atoms, and is able to predict the film coverage, deposition rate change, and microstructure of the deposited films. Both experimental and simulation results show that bottom coverage in trenches of aspect ratio 1.2 can be significantly improved from 50% to more than 80% using collimation. However, a penalty is paid by a corresponding decrease in deposition rate down to 15% of the uncollimated value. Additionally, the microstructure (grain size and orientation) is altered by collimation. The good agreement between the simulation and experimental results indicates that the model will be very useful for predicting and optimizing the properties of films deposited by collimated sputtering over topographical features.

Recent sulfur enrichment in the sediments of Little Rock Lake. Wisconsin

Multiple sediment cores collected from Little Rock Lake, Wisconsin, prior to experimental acidification show that total sulfur accumulation rates increased during the past century, with most of the increase occurring in the nonacid-volatile inorganic and organic fractions. The increased sulfur accumulation is a result of diagenetic processes within the sediments, rather than changes in seston deposition rates or terrestrial inputs. This enrichment has occurred because atmospheric sulfate deposition rates have increased over the past century, resulting in increased lake-water sulfate concentrations, which has, in turn, increased the diffusional flux to the sediments and increased the extent of diagenetic immobilization. Individual cores had markedly different sulfur accumulation rates, demonstrating the importance of collecting multiple cores to determine lakewide sediment accumulation.

In situ B-doped Si epitaxial films grown at 450‡ C by remote plasma-enhanced chemical vapor deposition: Physical and electrical characterization

In situ boron doping of Si epitaxial films grown at 450‡ C by remote plasma-enhanced chemical vapor deposition (RPCVD) has been studied using secondary ion mass spectroscopy (SIMS), Hall effect measurements, defect etching in conjunction with Nomarski microscopy, cross-sectional transmission electron microscopy (XTEM), and current-voltage measurements. Boron incorporation is shown to be controllable and electrically active from 7 × 1017 to over 1020 cm-3, with no dependence on process parameters (temperature, rf power, and substrate bias) in the ranges studied, other than the B2H6/SiH4 gas-phase ratio. No change in deposition rate upon introduction of B2H6 dopant gas is seen, contrary to what has been observed in several higher-temperature CVD processes. No defects such as stacking faults are seen under Nomarski microscopy, but a visible haze covers some areas ofin situ B-doped wafers. This haze appears to consist of amorphous cone-shaped structures with their apexes at the substrate-epilayer interface. The origin of the conical defects is believed to be related to some phenomenon at the initiation of growth. In order to evaluate the electrical quality ofin situ B-doped epilayers,P +/N mesa diodes have been fabricated using both homoepitaxial and heteroepitaxial (GexSi1-x)p-type epitaxial films. The electrical junction in these diodes coincides with the (epi-substrate)—interface in the grown films. To avoid interdiffusion or annealing effects during diode fabrication, all processing temperatures were kept at or below 450‡ C. Ideality factors are 1.2-1.3 for all diodes, indicating diffusion-limited transport rather than recombination in the depletion region.

Deposition of diamond-like carbon films by the anodic arc technique

The anodic vacuum arc is a powerful means of high rate deposition of thin films; besides a high degree of ionization, one of its interesting aspects is a strongly reduced droplet formation. Using graphite electrodes and adding hydrogen into the deposition chamber the preparation of diamond-like carbon films is possible, permitting an independent variation in the essential parameters. The films obtained show atomic number densities as a function of hydrogen content which are typical for diamond-like films prepared by conventional methods; the hydrogen content is determined by secondary-ion mass spectroscopy depth profiles. The dependence of the hydrogen content of the films on the gas flow is well characterized and saturation can be observed. This effect allows the deposition of homogeneous films even if the deposition rate changes locally or as a function of time. A comparison of IR spectra, hardness and mechanical stresses with data from films obtained by r.f. plasma chemical vapour deposition allows further characterization of these films.

Deposition of Fe-N films by means of an opposed targets sputtering type plasma source

Synthesis of Fe-N thin films were attempted by means of an opposed targets sputtering type plasma source. In this film preparation technique, both ions and neutral particles which are extracted from the plasma source are deposited on the substrate directly. Film deposition rate changes with substrate bias voltage Vs and takes a maximum value at a Vs around −30 V. This is mainly due to the increase in the amount of incident ions as the Vs decreases from 20 V to −30 V. The ion ratio in the deposited particles is estimated to be about 1/3 from the changes in the deposition rate with Vs. The increase in the amount of incident ions and in their energy suppresses the growth of the crystallites in the film significantly, which results in the decrease in coercive force of the films. The films deposited at a proper condition has a saturation magnetization of about 1700 emu/cc, coercive force below 0.8 Oe, and permeability at 1 MHz above 3000.

無電解銅めっき過程における析出速度の変化

無電解銅めっき過程における析出速度の変化