Carrier Gas Effects Research Articles

Theoretical prediction of a carrier gas effect under nucleation in thermal diffusion chambers

Analytical dependencies of critical supersaturation S * and ∂ S */∂ P on a carrier gas pressure P 0 and temperature T in a diffusion cloud chamber (DCC) are derived on the basis of the microscopic nucleation theory [A.L. Itkin, E.G. Kolesnichenko, Microscopic Theory of Condensation in Gases and Plasma, World Scientific, New York, 1997], specially modified for the case of diffusion-limited nucleation [A. Itkin, Kinetic model of effect of a carrier gas on nucleation in diffusion chamber, Aerosol Sci. Technol., in press], and a proper treatment of transport processes in a DCC. These dependencies qualitatively reproduce available experimental data. In addition, an effect of nature of both the carrier gas and condensing vapor on the observed phenomenon is discussed. The conclusion is made that the effect of the carrier gas in the experiments in a DCC has no connection to the real rate of chemical reactions of clusterization and, at other conditions (for instance, in expansion chambers), may not occur. Nevertheless, an existence of the carrier gas influence on the total nucleation rate can be of great importance for the control of nucleation.

Carrier gas effects on relative retention and resolution in capillary GLC

Carrier gas effects on relative retention and resolution in capillary GLC

Femtosecond laser interactions with methyl iodide clusters. I. Coulomb explosion at 795 nm

The study of the interaction of femtosecond laser radiation with matter, especially clusters, has blossomed in recent years due to advances in laser technology. One aspect of this interaction is Coulomb explosion. This effect occurs when the repulsive energy of like charges, known as Coulomb repulsion, overcomes the cluster’s total cohesive energy, causing the cluster to disintegrate into charged fragments. In this study, the interactions of methyl iodide clusters, formed in a supersonic expansion using argon and helium as carrier gases, were investigated at 795 nm using a Ti:Sapphire femtosecond laser. The resulting atomic and cluster ions were analyzed in a reflection time-of-flight mass spectrometer. The focus of these studies was the elucidation of the effects of carrier gas and laser wavelength on the laser-cluster interactions leading to Coulomb explosion. To achieve these goals, the effects of different carrier gases, laser power, cluster distribution, and the resulting Coulomb explosion energies were examined. A secondary consideration was to examine the experimental results with regard to the Coherent Electron Motion and Ionization Ignition models.

CVD Cu Process Development and Integration for sub-0.18 µm Devices

AbstractThe advent of inlaid Cu interconnects has presented new challenges for the industry to fill high aspect ratio dual inlaid features. CVD Cu offers advantages for excellent step coverage and is a technique extendible for future generations of devices. We have developed a robust CVD Cu process and a CVD/PVD reflow integration scheme. In this paper, we present results of an extensive study on CVD Cu process development and integration. The effects of various precursors, carrier gases (H2, He and N2) and barrier layers including CVD TiN, PVD Ta, PVD TaN, PVD Ta-Si-N, and a hybrid barrier, on the CVD Cu film properties and device electrical properties are discussed. The extendibility and challenges of current CVD Cu processing will also be discussed.

Effect of a carrier gas on nucleation in diffusion chambers

Diffusion cloud chambers (DCC) h ave frequently been employed when investigating homogeneous nucleation. The typical scheme of an experiment on studying nucleation in DCC is as follows (Heist et al., 1994). DCC usually consists of two horizontal plates top cold and bottom hot, but an inverse scheme has also been utilized (for instance, by (Lushnikov, 1997)). 0 ver the bottom plate there is a liquid which vapor condensation is a subject of the research. The space between plates is usually filled in with a background gas. By virtue of the existing distribution of temperature and pressure the vapor evaporating from the bottom surface moves due to diffusion through a chamber then cooling and again condensing. As a result of these processes an appropriate steady-state distribution of supersaturation S over the height of the chamber t ( usually reckoned from the bottom plate) is established. An occurrence of drops of the condensed vapor is detected by some kind of light-scattering or even visually. Since the vapor concentration in the chamber is low as compared with the concentration of the buffer gas, the processes of condensation do not practically influence the distribution of temperature and pressure over the height of the chamber which are determined only by the boundary conditions at the walls and by the carrier gas pressure PO. Moreover, it is possible to show that gradients of the temperature dlnT/dJ M 0.1 cm-’ and density realized in the chamber are small as compared with gradients of the clusters’ concentrations and in the first approximation may be neglected when describing the nucleation kinetics in DCC. Since the experimental investigations of the carrier gas effect on the nucleation rate in DCC became relatively popular it is possible to note from the literature that there is a trend to present the experimental data in coordinates S,(Po) or S,(T,) where S, is the supersaturation corresponding to J = 1 drop/cm3/s. Here we propose a new approach which combines a proper treatment of physical processes in DCC and new kinetic scheme of nucleation in the presence of the background gas (diffusion-limited kinetic of nucleation). Fist we analyze the transport processes in DCC with allowance for brownian diffusion, gravity, a drag and thermophoretic forces, that values depend on the cluster size or the Knudsen number specific for droplets and nucleation and the droplet growth and reveal their role with respect to the measured number of drops in DCC. Than we analyze what is the nucleation rate J actually determined in the experiment. Because usually experimental&s represent their results (in particular, J) as a function of S,, T, and PO where subscript “*” marks the point of the maximum supersaturation or a close point of the maximum nucleation rate, the main goal of this consideration is to express explicitly J through these parameters. However, for this pur

The carrier gas and surface passivation effects on selectivity in chemical vapor deposition of copper films

One of the interesting areas of Cu–CVD is the selective deposition, which attracts more attention based on its potential as a patterning method of Cu. The selectivity of CVD–Cu for SiO 2, TiN, and Al substrates was investigated systematically using (hfac)Cu(VTMS) with carrier gas of H 2 and Ar in the absence or presence of surface passivation process using HMDS as functions of the deposition temperature (150–200°C) and deposition time. The apparent incubation time on each substrate was increased as the conductivity of substrates and the deposition temperature were decreased. Moreover, H 2 carrier gas induced a shorter incubation time than Ar carrier gas for all conditions. HMDS in situ predosing process lengthened the incubation time on each substrate, temperature, and carrier gas. Its increment was larger on SiO 2 than TiN substrates, and was also larger under Ar than H 2 carrier gas ambient. It is thought that there is some competition between –OH passivation effect and –OH increment effect in the case of HMDS dosing under H 2 carrier gas atmosphere, but only the passivation effect is working under Ar carrier gas atmosphere.

Carrier gas effects on the selectivity in chemical vapor deposition of copper

One of the interesting areas of Cu-CVD is the selective deposition, which attracts more attention based on its potential as a patterning method of Cu. The selectivity of Cu-CVD for PECVD-SiO 2, TiN, and Al substrates was investigated systematically using a (hfac)Cu(VTMS) with carrier gas of H 2 and Ar as functions of deposition temperatures (150∼200°C), chamber pressures (0.3∼1.0 Torr), and deposition times. The apparent incubation time on each substrate was increased as the conductivity of substrates, the deposition temperature, and the chamber pressure were decreased. Moreover, H 2 carrier gas atmosphere had shorter incubation time, higher deposition rate, and smaller, better-connected Cu grains than Ar carrier gas. These are considered to be due to the increment of surface adsorption sites (–OH) of precursor in the case of H 2 carrier gas. This influence of H 2 on microstructural morphology of Cu films yielded lower resistivity than Ar. A minimum value obtained under H 2 atmosphere was 2.37 μΩ cm.

Dense carrier gas effect in vapor phase nucleation

By simple Monte Carlo simulation it is demonstrated that the capture of vapor molecules by a drop is affected by a dense background gas far from the Knudsen regime, and deep within the free molecule regime. The corresponding effect on steady-state nucleation is considered. For several representative examples the slopes of critical supersaturation vs carrier gas pressure are obtained and compared with experimental data.

Low temperature atmospheric pressure discharge plasma processing for volatile organic compounds

Abstract The 1,000 ppm VOCs (volatile organic compounds) decomposition performance of SPCP (Surfaced Discharge Induced Plasma Chemical Processing) was studied relating to various carrier gas effects, plasma exposing methods and others in order to understand the decomposition mechanisms. In any carrier gas, a direct SPCP can decompose every VOC tested. The efficient decomposing carrier gases are oxygen, air and nitrogen in that order. However, when the SPCP treated gasses (air, nitrogen or oxygen) are mixed with contaminated gasses, oxygen seems be necessary to decompose VOCs. Four new halogenated (chloro-)organic materials are also tested as contaminants. The maximum decomposition for every contaminants is found to be more than 90% and the energy efficiency for each contaminant is roughly in the same order.

Effect of Carrier Gases on the Chemical Vapor Deposition of Tungsten from WF 6 ‐ SiH4

Effect of carrier gases like argon, helium, and hydrogen on the deposition rate and properties of CVD tungsten from was studied. Each carrier gas has different momentum and thermal diffusivity, and the mean free path and mass diffusivity of reactant molecules are also different. This has a significant effect on the deposition rate, film composition, and film morphology. A carrier gas with high thermal diffusivity and high molecular velocity like helium lowers the deposition rate considerably because gas‐phase formations of intermediate species, which go out of the reactor, are favorable. The film looks like powdery aggregates and shows poor adhesion. Effect of the carrier gases on the step‐coverage, grain size, chemical composition, and electrical resistivity was identified from the experiment.

Nitrous oxide decreases solubility of isoflurane and halothane in blood.

This study investigated the effects of carrier gases on the solubility of isoflurane or halothane in blood. The blood/gas partition coefficients (lambda blood/gas) of 1 minimum alveolar anesthetic concentration of isoflurane or halothane in 100% oxygen, 30% oxygen with 70% nitrous oxide, 100% nitrous oxide or air were measured at 37 degrees C, with blood from four donors. The values of isoflurane or halothane in 100% nitrous oxide (1.42 +/- 0.03; 2.59 +/- 0.05) were lower (P < 0.05) than those obtained when using 100% oxygen (1.53 +/- 0.02; 2.71 +/- 0.05) or air (1.54 +/- 0.03; 2.74 +/- 0.05). To determine the effect of absence of oxygen in the blood containing nitrous oxide on solubility, lambda blood/gas of 1 minimum alveolar anesthetic concentration of isoflurane or halothane in 100% oxygen, a gas mixture (30% oxygen and 70% nitrous oxide) or 100% nitrous oxide were measured under the same conditions. The values of isoflurane or halothane in 100% nitrous oxide (1.29 +/- 0.03; 2.25 +/- 0.08) and in a gas mixture of 30% oxygen and 70% nitrous oxide (1.33 +/- 0.04; 2.29 +/- 0.05) were lower (P < 0.05) than those obtained with 100% oxygen (1.40 +/- 0.03; 2.37 +/- 0.04). We conclude that nitrous oxide decreases the lambda blood/gas of isoflurane or halothane, and that this change of solubility, although small, increases the uptake rate of halothane or isoflurane.

Effects of solvents and carrier gases on the electrical and optical properties of pyrosol-deposited SnO2-based films

SnO2-based films have been prepared by the pyrosol deposition method, and the dependence of their electrical and optical properties on solvent (CH3OH, H2O) concentration in the solution and the nature of the carrier gas (air, N2) has been investigated. The electrical resistivity of the films obtained using air as the carrier gas decreases as the CH3OH:H2O mole ratio increases to 2–3, and then increases with further increase in the CH3OH:H2O ratio. The optical transmittance exhibits a gradual decrease with the CH3OH:H2O ratio. The use of N2 as the carrier gas always leads to the production of much more resistive and less transparent films owing to the much lower Hall mobility, but the electrical resistivity of the films increases sharply with increasing CH3OH:H2O ratio. The variations in the Hall mobility as a function of the CH3OH:H2O ratio and the nature of the carrier gas seem to be in good agreement with the changes in the surface morphology, which in turn are well reflected by the X-ray diffraction analysis. These two experimental parameters governing the total amount of oxidizing agents included in the solutions appear also to affect the chemical composition of the films, but their influences are not significant enough to explain all the variations in the electrical and optical properties.

Atomic layer epitaxy of GaAs using N 2 carrier gas

Carrier gas effects on the atomic layer epitaxial (ALE) conditions and the electrical quality of GaAs are investigated. ALE is achieved over a relatively wide temperature range of 490 to 520°C using nitrogen carrier gas. For hydrogen carrier gas, the corresponding temperature range for ALE growth is only from 490 to 500°C. Gas analysis of TMG reveals that this is due to the suppression of TMG decomposition in nitrogen. The use of nitrogen reduces carbon incorporation in the epilayers by about one order of magnitude (compared to hydrogen) by promoting the arsine decomposition. The stoichiometry of the ALE layer related to deep defects is clarified and a possible way to reduce them is proposed.

Rotational spectrum and structure of the linear CO2–HCN dimer: Dependence of isomer formation on carrier gas

A linear hydrogen-bonded dimer, OCO–HCN, has been identified and characterized via its microwave rotational spectrum. The study was made using the pulsed nozzle Fourier transform method with the Flygare/Balle Mark II spectrometer. A T-shaped HCN–CO2 dimer was reported earlier by the Klemperer group. Rotational constants have been determined for all seven monoisotopically substituted species of the linear form. B0 , DJ , and χaa (14 N) for the normal isotopic dimer are 1057.9397(2) MHz, 1.372(8) kHz, and −4.2466(5) MHz, respectively. The average torsional displacements of the OCO and HCN monomers about their center of mass (c.m.) are found to be 7.66° and 12.40°, based on the substitution O–C and C–N bond distances for the dimer. With these values for α and γ, the B0 for the normal isotopic dimer corresponds to a c.m. to c.m. distance R=5.035 Å. Bending and stretching force constants and the well depth (ε∼590 cm−1 ) are estimated from the centrifugal distortion. The relative concentrations of the linear and T-shaped isomers are unusually sensitive to the carrier gas used in the supersonic jet expansion. The linear form could not be detected at all with argon as the carrier gas but gave a strong signal in neon first run (70% Ne, 30% He). In contrast, the T form gave strong signals in both carrier gases. However, a carrier-gas effect was not found for the N2 O/HF dimer pair, which has a high barrier between the bent NNO–HF and linear FH–NNO isomers. Similar results were obtained for chlorocyclohexane (CCH) and ethyl formate (EF), which have two conformational isomers. In CCH which has a high barrier to a↔e interconversion, the two conformers gave strong signals in both Ar and He. In EF, with a low barrier, the gauche conformer could not be detected in Ar but gave a strong signal in He, while the trans form gave strong signals in both carrier gases.

On the history of cluster beams

The methods to produce and investigate cluster beams have been developed primarily with the use of permanent gases. A summary is given of related work carried out at Marburg and Karlsruhe. The report deals with the effect of carrier gases on cluster beam production; ionization, electrical acceleration and magnetic deflection of cluster beams; the retarding potential mass spectrometry of cluster beams; cluster size measurement by atomic beam attenuation; reflection of cluster beams at solid surfaces; scattering properties of 4He and 3He clusters; the application of cluster beams in plasma physics, and the reduction of space charge problems by acceleration of cluster ions.

Molecular Structure of Plasma-polymerized Methyl Methacrylate and Evaluation as a Resist

種々のキャリヤーガスプラズマ下流にメタクリル酸チルモノマーを混入して重合膜を基板上に形成した。重合速度やエッチング速度のキャリヤーガス依存性を調べるとともに,重合膜のIR,ESCA,NMR測定を行ない,分子構造,反応機構を検討した。さらに,この重合膜を電子線X線で描画し,その潜像をプラズマエッチングによって現嫁し,レジストとしての特性を評価した。この結果・不活性ガスをキャリヤーガスとしたときはラジカル性の反応が主要な反応機構であり,分子構造も通常の高分子に類似したものであることがわかった。他方,酸素などの反応性ガスの場合,イオン性反応が観測され,分子構造も通常の高分子とは異なっていることがわかった。レジストとしての特性は,ドライ現嫁する場合は,プラズマ重合したものが通常の高分子よりも高感度となり,描画パターンの現像ができた。しかし,実用的なレジスト感度を得るためには,さらに増感剤の混入などの対策が必要なことがわかった。

Calculations of carrier gas effects in non-dispersive infrared analyzers. II. Comparisons with experiment

A numerical model for calculating carrier gas effects in non-dispersive infrared gas analyzers was presented in the preceding paper. This model is applied here to sets of data from several analyzers used in measuring atmospheric CO 2 concentrations at a world-wide network of baseline stations. The agreement between the model and the experimental results is generally satisfactory, and the model can be used to better understand the behaviour of non-dispersive analyzers.DOI: 10.1111/j.2153-3490.1982.tb01828.x

Calculations of carrier gas effects in non-dispersive infrared analyzers I. Theory

A theory and method of calculation is presented for determining changes in instrument response and hence apparent gas concentration which arise in non-dispersive infrared gas analyzers when gas mixtures with varying carrier gases are analyzed. The theory is based on variations in pressure-broadening in the sample cell of the analyzer and initial comparisons with experimental values for CO 2 -in-air and CO 2 -in-N 2 indicate good agreement between theory and experiment. DOI: 10.1111/j.2153-3490.1982.tb01827.x

Calculations of carrier gas effects in non-dispersive infrared analyzers. II. Comparisons with experiment

A numerical model for calculating carrier gas effects in non-dispersive infrared gas analyzers was presented in the preceding paper. This model is applied here to sets of data from several analyzers used in measuring atmospheric CO 2 concentrations at a world-wide network of baseline stations. The agreement between the model and the experimental results is generally satisfactory, and the model can be used to better understand the behaviour of non-dispersive analyzers.DOI: 10.1111/j.2153-3490.1982.tb01828.x

Calculations of carrier gas effects in non-dispersive infrared analyzers I. Theory

Calculations of carrier gas effects in non-dispersive infrared analyzers I. Theory