Showing papers on "Chemical vapor deposition published in 1984"

A Mathematical Model of the Coupled Fluid Mechanics and Chemical Kinetics in a Chemical Vapor Deposition Reactor

Abstract: We describe a numerical model of the coupled gas‐phase hydrodynamics and chemical kinetics in a silicon chemical vapor deposition (CVD) reactor The model, which includes a 20‐step elementary reaction mechanism for the thermal decomposition of silane, predicts gas‐phase temperature, velocity, and chemical species concentration profiles It also predicts silicon deposition rates at the heated reactor wall as a function of susceptor temperature, carrier gas, pressure, and flow velocity We find excellent agreement with experimental deposition rates, with no adjustment of parameters The model indicates that gas‐phase chemical kinetic processes are important in describing silicon CVD

Chemical beam epitaxy of InP and GaAs

Abstract: A new epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis of either trimethylindium or triethylindium and trimethylgallium or triethylgallium at the heated substrate surface, respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine and trimethylarsine in contact with heated Ta or Mo at 950–1200 °C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reach the substrate surface by diffusing through a stagnant carrier gas boundary layer above the substrate, the chemicals in CBE were admitted into a high vacuum growth chamber and impinged directly light of sight onto the heated substrate surface in the form of molecular beams. The beam nature of CBE resulted in efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A gas h...

Selective Low Pressure Chemical Vapor Deposition of Tungsten

Abstract: We have examined the kinetics of low pressure chemical vapor deposition of tungsten by the hydrogen and silicon reduction of within a pressure range of 0.1–5 torr and a temperature range of 250°–500°C. The rate‐limiting mechanism for the hydrogen reduction system was determined to be the dissociation of adsorbed on the surface, with an activation energy of 0.71 eV. A self‐limiting deposit results from the reaction, the thickness and structure of which are dependent upon the initial native oxide characteristics. Deposition occurs selectively on materials that react directly with or yield monatomic hydrogen. In the presence of hydrogen, the degree of selectivity is a function of temperature, substrate material, and surface cleanliness.

Growth and Physical Properties of LPCVD Polycrystalline Silicon Films

Abstract: Undoped LPCVD silicon films have been deposited at five temperatures between 560° and 620°C. The films were characterized as grown and after thermal annealing at 900°, 950°, and 1000°C. We used x‐ray diffraction, TEM, SEM, Raman and elastic light scattering, optical absorption and reflection, and other techniques in order to obtain information on the grain size, structure, structural perfection, and surface roughness. We found that polysilicon films of good structural perfection, low strain, and small surface roughness are obtained when the films are deposited in the amorphous phase and subsequently crystallized at 900°–1000°C. Such films are superior in all investigated material aspects to films grown in the crystalline phase.

‘‘Buffer‐layer’’ technique for the growth of single crystal SiC on Si

Abstract: The nature of the buffer layers needed for the single crystal deposition of cubic SiC on Si substrates was studied. It is concluded that the buffer layer is a stressed monocrystalline layer of cubic SiC.

Ion-assisted deposition of optical thin films: low energy vs high energy bombardment

Abstract: Oxygen ion-assisted deposition of SiO2 and TiO2 has been investigated as a function of ion energy (30–500 eV) and current density (0–300 μA/cm2) at the optic. It is shown that both low and high energy ion bombardment improve SiO2 film stoichiometry, although slightly greater improvement is realized for the low energy case. For TiO2 films, low energy bombardment improves stoichiometry, while high energy bombardment is clearly detrimental. A reduction in H content by a factor of 10 is observed in SiO2 films deposited with high energy ion bombardment. Durable films are produced at low substrate temperatures (50–100°C). Film stress characteristics are discussed.

Emergent Process Methods for High-Technology Ceramics

Abstract: The present conference covers colloidal processing of advanced ceramics, novel power-forming and powder-processing methods, the derivation of ceramics by polymer processing, chemical vapor deposition techniques, ion beam deposition methods, the laser and ion beam modification of surfaces, hot isostatic pressing and dynamic compaction, shock conditioning and subsequent densification of ceramics, and very high pressure processing methods. Specific attention is given to the preparation of shaped glasses by the sol-gel method, the synthesis of powders and thin films by laser-induced gas phase reactions, the plasma sintering of ceramics, laser chemical vapor deposition, the microstructure and mechanical properties of ion-implanted ceramics, a computer simulation of dynamic compaction, shock-induced modification of inorganic powders, and diamond anvil technology.

High‐temperature electrical properties of 3C‐SiC epitaxial layers grown by chemical vapor deposition

Abstract: Electrical properties of 3C‐SiC layers, epitaxially grown on silicon by chemical vapor deposition, have been investigated at the temperatures between room temperature and 850 °C. In this temperature range, the electron mobility changes with temperature as μH∼T−1.2∼−1.4. The weaker temperature dependence of mobility and the larger mobilities compared with other polytypes of SiC suggest that 3C‐SiC is a promising material for devices operated at high temperatures.

Characterization of LPCVD Aluminum for VLSI Processing

Abstract: Aluminum and aluminum alloys are widely used for metallizing devices in VLSI processing. Such films can be deposited by a variety of techniques, which all presently suffer from inadequate step coverage. In this paper, we discuss the properties of aluminum films deposited by a low pressure chemical vapor deposition process using tri‐isobutyl aluminum as a source. Results of this work demonstrate that this process provides conformal step coverage, introduces no surface states, and promises to yield high wafer throughput. Films deposited on oxidized silicon monitors exhibit excellent properties in terms of chemical purity, adhesion, and electrical resistivity. Films deposited on device wafers prove to be compatible with current VLSI processing in terms of patterning, dry etching, and bondability and appear to have no effect on overall device performance. However, drawbacks of LPCVD aluminum appear to be in its structure‐related properties: namely, electromigration resistance and Al‐Si interdiffusion. These problems and potential solutions are addressed.

Phosphorus‐Doped Polycrystalline Silicon via LPCVD I . Process Characterization

Abstract: We have studied the low pressure chemical vapor deposition (LPCVD) process as applied to the preparation of in situ phosphorus‐doped polycrystalline silicon films. Thickness profiling, electron microprobe, and mass spectrometry have been utilized in the characterization of this process. The addition of phosphine as the dopant bearing precursor molecule was found to result in a factor of 25 decay in film growth rates relative to the intrinsic LPCVD process. The physical and chemical characteristics of samples prepared in this manner are shown to be a strong function of local reactor geometry, with growth‐rate variations of a factor of two within a wafer commonly observed. Mass spectrometry data is presented supporting the proposal that phosphine passivates the silicon surface, and the implications of this phenomenon for altering silicon growth kinetics are discussed. A model is presented accounting for the growth‐rate variations observed within individual wafers, as well as for the sensitivity of the phosphine‐doped process to system geometry.

Study of the atomic models of three donorlike defects in silicon metal‐oxide‐semiconductor structures from their gate material and process dependencies

Abstract: The atomic models of the generation and annealing of three donorlike defects [the bulk compensating donor, the donorlike interface density‐of‐state (DOS) peak, and the positive turn‐around charge] in silicon metal‐oxide‐semiconductor capacitors (MOSC) are investigated by studying their dependencies on the gate materials and process conditions. Starting thermal oxides used in this study include 1000 C dry oxides on 〈100〉 p‐Si substrates and 750 C high‐pressure steam oxides on 〈111〉 p‐Si substrates. Gate materials include aluminum, gold, and LPCVD (low‐pressure chemical‐vapor‐deposition) polycrystalline silicon (poly‐Si) with several doping methods. The densities of these donors generated during avalanche electron injection in MOSC’s with boron in situ doped LPCVD poly‐Si gates are smaller compared with those with aluminum gates. High temperature (>900 C) processes (diffusion or anneal) in dry inert gas after the poly‐Si gate deposition inhibit the generation of all three donors. After the inhibition, the d...

Chemical vapor deposition apparatus

Abstract: An improved chemical vapor deposition device having heating means (6,8) substantially surrounding an inner deposition chamber (32) for providing isothermal or precisely controlled gradient temperature conditions therein. The internal components of the chamber are quartz or similar radiant energy transparent material. Also included are special cooling means to protect thermally sensitive seals, structural configurations strengthening areas of glass components subjected to severe stress during operation, and specific designs permitting easy removal and replacement of all glass components exposed to deposition gas.

Chemical vapor deposition apparatus

Abstract: A chemical vapor deposition apparatus has a reactor divided into a reaction space and a purging space by a susceptor for supporting a wafer and a loading chamber communicated through a gate with the reactor. Exhaust units are communicated with the reactor and loading chamber, respectively, so that the pressures in the reactor and loading chamber may be reduced. The susceptor has a plurality of recesses to aid placing or scooping the water. Through a transparent wall on the side of the purging space, the susceptor is heated by a lamp unit disposed outside the transparent wall. The loading chamber includes a wafer transport mechanism for charging a wafer into the reactor or discharging a processed wafer from the reactor. An unprocessed wafer is loaded to the loading chamber from a cassette and the processed wafer is unloaded to the cassette. One or a small number of wafers are processed at one time. A uniform film is deposited with a high reproducibility. The processing rate is high and the chemical vapor deposition apparatus is made compact in size.

SiC filament/titanium matrix composites regarded as model composites Part 1 Filament microanalysis and strength characterization

Abstract: Two types of large diameter SiC CVD filaments have been investigated on both chemical and mechanical standpoints: a 100#m filament with a tungsten core (from SNPE) and three 140#m filaments with carbon cores and surface coatings (from AVCO). On the basis of microprobe (X-ray, Auger and Raman), X-ray diffraction and SEM analyses, it appears that the former is made of a single homogeneous stoichiometric SiC deposit while the latter are mainly made of two concentric shells (the inner being a SiC+C mixture and the outer almost pure SIC). All the C-core filaments had received a surface coating (either pure pyrocarbon or SiC+C mixture) presumably to protect the brittle SiC deposit against abrasion due to handling in opposition to the W-core filament which seems to have no surface coating at all. The W-core filament, although smaller in dia- meter, is weaker than the C-core filaments (average UTS of 3 and 4 GPa respectively for a 40 mm gauge length). However, its strength distribution is much narrower (We/bull moduli of 7-8 and 2-5 respectively). Failures of most filaments appear to have a multi- modal character.

Patterned photonucleation of chemical vapor deposition of Al by UV‐laser photodeposition

Abstract: UV‐laser photodeposition has been used to predispose surfaces to pyrolytic chemical vapor deposition (CVD) of Al from triisobutylaluminum. Two laser beam (UV and IR) experiments indicate that the predisposition is due to the formation of a catalytic surface for heterogeneous chemistry. Time‐resolved transmission measurements indicate that a few photodeposited monolayers are sufficient to nucleate CVD growth. The technique may be generally useful for maskless patterned growth by CVD processes with large nucleation barriers.

Metalorganic Chemical Vapor Deposition of III-V Semiconductors

Abstract: Metalorganic chemical vapor deposition (MOCVD) is a process in which two or more metalorganic chemicals (for instance, trimethylgallium) or one or more metalorganic sources and one or more hydride sources (for instance, arsine, AsH(3)) are used to form the corresponding intermetallic crystalline solid solution MOCVD materials technology is a vapor-phase growth process that is becoming widely used to study the basic physics of novel materials and to grow complex semiconductor device structures for new optoelectronic and photonic systems The MOCVD process is described and some of the device applications and results that have been realized with it are reviewed, with particular emphasis on the III-V compound semiconductors

Phosphorus‐Doped Polycrystalline Silicon via LPCVD II . Surface Interactions of the Silane/Phosphine/Silicon System

Abstract: Secondary ion mass spectrometry (SIMS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES) have been employed to study the interactions of silane and phosphine with the Si(100) surface. Phosphine adsorption and desorption were investigated at surface temperatures in the range . At ambient temperature, phosphine saturated the bare Si(100) surface after 3–5L exposure, and fitting adsorption data to a Langmuir model yields the value for the sticking coefficient. Phosphine adsorption was found to follow the pattern of the underlying silicon. Competitive adsorption experiments set an upper bound of for silane adsorption under like conditions. The silicon surface was observed to be passivated with respect to silane adsorption by prior exposure to phosphine, with a layer of preferentially adsorbed phosphine formed which served to preclude subsequent silane adsorption. The results obtained here are discussed in the context of their bearing upon the phosphorus‐doped low pressure chemical vapor deposition process.

GaAs1−xSbx growth by OMVPE

Abstract: The system GaAs1−xSbx has a solid phase miscibility gap ranging from x = 0.2 to x = 0.8 at the typical growth temperature of 600 C; however, metastable alloys covering this entire composition range have been grown by organometallic vapor phase epitaxy (OMVPE) using trimethylgallium, antimony and -arsenic as the source materials. The solid composition is studied for various values of growth temperature, the ratio of Sb to total group V elements in the vapor phase and the ratio of group III to group V elements in the vapor phase. The fraction of trimethylarsenic (TMAs) pyrolyzed in the vapor phase is found to be < 1 and to vary with temperature. Taking into account the incomplete pyrolysis of TMAs, solid composition is found to be controlled by thermodynamics. The effects of temperature and vapor composition are all accurately predicted using a simple thermodynamic model assuming equilibrium to be established at the solid-vapor interface. The properties of these metastable GaAs1−x Sbx alloys were explored using interference contrast microscopy, room temperature and 4 K photoluminescence, Hall effect and conductivity measurements. The alloy GaAs0.5Sb0.5 grown lattice matched to the InP substrate has excellent surface morphology, is p-type, and the photoluminescence spectrum consists of a single, intense, fairly broad (23.5 meV half width) peak at a wavelength of 1.54 Μm.

Thermal oxidation of 3C silicon carbide single‐crystal layers on silicon

Abstract: Thermal oxidation of thick single-crystal 3C SiC layers on silicon substrates was studied. The oxidations were conducted in a wet O2 atmosphere at temperatures from 1000 to 1250 C for times from 0.1 to 50 h. Ellipsometry was used to determine the thickness and index of refraction of the oxide films. Auger analysis showed them to be homogeneous with near stoichiometric composition. The oxide growth followed a linear parabolic relationship with time. Activation energy of the parabolic rate constant was found to be 50 kcal/mole, while the linear rate constant was 74 kcal/mole. The latter value corresponds approximately to the energy required to break a Si-C bond. Electrical measurements show an effective density of 4-6 x 10 to the 11th per sq cm for fixed oxide charges at the oxide-carbide interface, and the dielectric strength of the oxide film is aproximately 6 x 10 to the 6th V/cm.

Plasma‐enhanced CVD: Oxides, nitrides, transition metals, and transition metal silicides

Abstract: Plasma‐enhanced chemical vapor deposition (PECVD) of thin films has generated considerable interest in recent years. Much of this interest stems from the ability of high energy electrons in rf glow discharges (plasmas) to break chemical bonds and thereby promote chemical reactions at or near room temperature. Such considerations are particularly important when depositing films onto substrates which cannot withstand high temperatures. A further advantage, however, is that the highly reactive plasma atmosphere can result in the formation of materials with unique chemical, physical, and electrical properties. In this paper, the plasma‐enhanced deposition of oxide, nitride, transition metal, and transition metal silicide films will be discussed. Emphasis will be placed upon the chemistry occurring in the glow discharge, and on the manner in which this chemistry controls the resulting film properties.

GaAs light‐emitting diodes fabricated on Ge‐coated Si substrates

Abstract: Light‐emitting diodes have been fabricated in GaAs grown by metalorganic chemical vapor deposition on vapor‐deposited epitaxial Ge films on Si substrates. The light‐emitting junction was formed by zinc diffusion into the n‐type GaAs layer. Room‐temperature light emission centered at 872 nm has been observed.

Process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition

Abstract: A chemical vapor deposition (CVD) process for preparing fiber-reinforced ceramic composites. A specially designed apparatus provides a steep thermal gradient across the thickness of a fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

Low resistivity tungsten silicon composite film

Abstract: A composite film is provided which has a first layer of WSix, where x is greater than 2, over which is disposed a second layer of a tungsten complex consisting substantially of tungsten with a small amount of silicon therein, typically less than 5%. Both layers are deposited in situ in a cold wall chemical vapor deposition chamber at a substrate temperature of between 500° and 550° C.. Before initiating the deposition process for these first and second layers, the substrate onto which they are to be deposited is first plasma etched with NF3 as the reactant gas, then with H2 as the reactant gas, both steps being performed at approximately 100 to 200 volts self-bias. WSix is then deposited onto the surface of the substrate using a gas flow rate for silane which is 20 to 80 times the flow rate of tungsten silicide, followed by deposition of a tungsten complex as the second layer, using a gas flow rate for tungsten hexafluoride which is 1 to 3 times the flow rate of silane, and a gas flow rate of hydrogen which is about 10 times the flow rate of silane. Similarly, in another embodiment, the tungsten complex without the silicide layer is deposited directly onto a silicon surface using the same process as for the tungsten complex in the second layer of the first embodiment.

Refractive index and inhomogeneity of thin films.

Abstract: The fact that the optical characteristics of thin-film materials are generally different from those of the same materials in bulk form is well known. The differences depend very much on the conditions in which the deposition has been carried out. A good understanding of these differences, their causes, and the influence of deposition parameters is vital if we are to be able to improve coating quality. We have developed two complementary methods with the objective of deriving information on the index of refraction and its variation throughout the thickness of the film. Perceptible optical inhomogeneity is normally present and appreciable inhomogeneity is frequently present in thin films. Such inhomogeneity is usually associated with layer microstructure. The first is a postdeposition technique that makes use of measurements in air of the transmittance and reflectance of the layer under study over a wide wavelength region. The second, in contrast, makes use of in situ measurements, that is measurements made under vacuum and during the actual deposition of the layer. We shall show with the help of several examples that the two methods lead to results that are consistent and demonstrate the existence in deposited materials of an inherent variation of the index of refraction normal to the surface. The thermal sensitivity of the layer properties and their tendency to adsorb atmospheric moisture must be taken into account before the residual differences between the two techniques can be explained.

GaN blue light emitting diodes prepared by metalorganic chemical vapor deposition

Abstract: The epitaxial layers of GaN have been grown on (0001)‐oriented sapphire substrates using metalorganic chemical vapor deposition. The layers with good quality and relatively smooth surface morphology were obtained by enforcing growth in H2 after adherence of nuclei to the substrates in N2 atmosphere. Using this technique, GaN light emitting diodes with metal‐insulating n‐type structure were fabricated. Two kinds of blue electroluminescence were observed at room temperature with exciting voltage of 4–8 V with emission wavelength of 430 and 488 nm. The external efficiency is about 0.005%.

Tunable cut-off UV detector based on the aluminum gallium nitride material system

Abstract: A method of preparing a UV detector of Al x Ga 1-x N. Metal organic chemical vapor deposition (MOCVD) is utilized to grow AlN and then Al x Ga 1-x N on a sapphire substrate. A photodetector structure is fabricated on the AlGaN.