Pressure Chemical Vapor Deposition Reactor Research Articles

A Monte Carlo Simulation Study of Radiation Heat Transfer in the Multiwafer LPCVD Reactor

A direct simulation Monte Carlo technique is used to simulate the radiation heat transfer in a multiwafer low pressure chemical vapor deposition (LPCVD) reactor. The model accounts for the heat transfer between the stack of closely spaced Si wafers, the quartz reactor tube, the stainless steel ends of the reactor, and the surrounding furnace. Spectral and thermal variations in the materials properties are included directly in the model. In addition, conductive heat transfer through the quartz tube is computed using a finite difference approach. The cooled ends of the reactor result in a suppression of the temperature of several wafers at each end of the wafer stack. Simulations show that the extent of this cooling effect is influenced by direct radiative heat losses from the end wafers as well as dissipation of the furnace heat flux by conductive heat losses through the quartz tube. The calculated temperature profiles are then used as thermal boundary conditions in simulations of rarefied gas flows in the LPCVD reactor. The thermal variations along the quartz and wafer surfaces give rise to significant temperature and density variations in the gas flow. The simulation results show excellent agreement with experimental data.

Crystal silicon Fabry-Perot cavities deposited with dichlorosilane in a reduced pressure chemical vapour deposition reactor for thermal sensing

A surface-normal Fabry-Perot (FP) thermal sensor with embedded multiple QW dielectric mirrors, was fabricated and evaluated using a single crystal merged silicon epitaxial lateral overgrowth (MELO) technique. The sensitivity of the sensor has been improved owing to the higher finesse.

Polysilicon Fabry-Perot cavities deposited with dichlorosilane in a reduced pressure chemical vapour deposition reactor for thermal sensing

Polysilicon Fabry-Perot cavities deposited with dichlorosilane in a reduced pressure chemical vapour deposition reactor for thermal sensing

Low Temperature Atmospheric Pressure Chemical Vapor Deposition of Group 14 Oxide Films

ABSTRACTDepositions of high quality SiO2 and SnO2 films from the reaction of homoleptic amido precursors M(NMe2)4 (M = Si, Sn) and oxygen were carried out in an atmospheric pressure chemical vapor deposition reactor. The films were deposited on silicon, glass and quartz substrates at temperatures of 250 to 450 °C. The silicon dioxide films are stoichiometric (O/Si = 2.0) with less than 0.2 atom % C and 0.3 atom % N and have hydrogen contents of 9 ± 5 atom °. They are deposited with growth rates from 380 to 900 Å/min. The refractive indexes of the SiO2 films are 1.46, and infrared spectra show a possible Si-OH peak at 950 cm−1. X-Ray diffraction studies reveal that the SiO2 film deposited at 350°C is amorphous. The tin oxide films are stoichiometric (O/Sn = 2.0) and contain less than 0.8 atom % carbon, and 0.3 atom % N. No hydrogen was detected by elastic recoil spectroscopy. The band gap for the SnO2 films, as estimated from transmission spectra, is 3.9 eV. The resistivities of the tin oxide films are in the range 10−2 to 10−3 Ω cm and do not vary significantly with deposition temperature. The tin oxide film deposited at 350°C is crystalline cassitterite with some (101) orientation.

Structural Differences Between Cvd And Thermally Grown Amorphous SiO2

AbstractThe structure and density of amorphous S1O2 films grown by chemical vapor deposition (CVD) or thermal oxidation are studied by Fourier-transform infrared (FT-IR) absorption, neutron diffraction, and Rutherford backscattering (RBS) measurements. CVD oxides, formed in an atmospheric-pressure CVD reactor with a SiH4-O2 gas mixture at 400 °C, are compared with thermal oxides, grown at 980 °C in H2-O2 atmosphere. The average Si-O-Si bond angle deduced from the stretching frequency of FT-IR is found to be smaller in CVD oxides than in thermal oxides, and the density revealed by RBS measurements is found to be a little lower in CVD oxides than in thermal oxides. These differences are explained by the medium-range structural disorder revealed by FT-IR measurements as well as by neutron diffraction measurements. The medium-range structural disorder in CVD oxides is responsible for large silanol content in the oxides and is the origin in difference between CVD and thermal oxides.

Modeling the Wafer Temperature Profile in a Multiwafer LPCVD Furnace

A mathematical model has been developed to predict wafer temperatures within a hot‐wall multiwafer low pressure chemical vapor deposition (LPCVD) reactor. The model predicts both axial (wafer‐to‐wafer) and radial (across‐wafer) temperature profiles. Model predictions compare favorably with in situ wafer temperature measurements described in an earlier paper. Measured axial and radial temperature nonuniformities are explained in terms of radiative heat‐transfer effects. A simulation study demonstrates how changes in the outer tube temperature profile and reactor geometry affect wafer temperatures. Reactor design changes which could improve the wafer temperature profile are discussed.

Epitaxial LiTaO3 thin film by pulsed metalorganic chemical vapor deposition from a single precursor

Epitaxial LiTaO3 thin films were grown on (0001) sapphire in a low pressure chemical vapor deposition reactor of a new design, using lithium tantalum hexa-t-butoxide as the precursor. X-ray diffraction shows that the LiTaO3 c axis is normal to the sapphire surface. The x-ray pole figure and cross-section transmission electron microscopy diffraction show that the films were also in-plane oriented, with sapphire [101̄0] parallel to lithium tantalate [101̄0]. The refractive index of the film compares well with bulk values, over a wide wavelength range.

The Anisotropic Deposition of Doped Silicate Glass

In this letter we present initial results for the anisotropic deposition of doped silicate glass. The deposition was performed in a previously described low pressure chemical vapor deposition reactor by the reaction of tetraethylorthosilicate, triethyl borate, phosphine, and oxygen. The depositions were performed over a nominal temperature range of 973 to 1023 K. Results presented here indicate that the glass deposits anisotropically over polysilicon structures on silicon substrates favoring high surface density corners to lower surface density flat areas of the silicon substrates.

Predicting intrawafer film thickness uniformity in an ultralow pressure chemical vapor deposition reactor

We present a reaction engineering analysis of a multiple wafer-in-tube ultrahigh vacuum chemical vapor deposition reactor which allows an estimate of wafer throughput for a reactor of fixed geometry and a given deposition chemistry with specified film thickness uniformity constraints. The model employs a description of ballistic transport and reaction based on the pseudosteady approximation to the Boltzmann equation in the limit of pure molecular flow. The model representation takes the form of an integral equation for the flux of each reactant or intermediate species to the wafer surfaces. Expressions for the reactive sticking coefficients (RSC) for each species must be incorporated in the term which represents reemission from a wafer surface. In our model we use a published expression for the RSC of silane as a function of flux and wafer temperature developed from molecular beam measurements. Numerical solution of the resulting integral equation using Gauss–Legendre quadrature yields quantitative estimates of intrawafer film thickness uniformities for epitaxial silicon deposition from silane for specified process conditions and wafer radius:wafer separation. For given reactor dimensions and specified uniformity, throughputs can then be estimated.

Particle contamination in low pressure organometallic chemical vapor deposition reactors: Methods of particle detection and causes of particle formation using a liquid alane (AlH3) precursor

Two methods of analyzing particles were interfaced to a low pressure chemical vapor deposition reactor used to deposit Al films from the liquid precursor dimethylethylamine alane. A laser light scattering particle counter was used to monitor particles (≳200 nm) in real time and established that the appearance of particles corresponded to the flow of precursor into the reactor. A particle impaction system was used to collect particles (≳20 nm) for analysis using analytical transmission electron microscopy and electron diffraction. Typical sizes of the Al particles were in the range 20–1000 nm. Purposely introducing trace amounts of H2O, CO, and O2 into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that Al particle formation was induced by impurities in the gas phase (particularly H2O) although competing mechanisms could not be ruled out.

Phosphorus doping of epitaxial Si and Si1−xGex at very low pressure

We report on the in situ P doping of Si1−xGex(SiH4/GeH4) and Si(SiH4) epitaxial films with 1–100 ppm PH3 at 620 °C in a very low pressure chemical vapor deposition reactor. The epitaxial growth rates were found to decrease with P doping. The growth rate reduction is a function of Ge composition and is less pronounced as the Ge content increases. In addition, P incorporation into the growing film is affected by Ge, which improves the concentration range and profile definition of P. A simple model that attempts to explain the results is discussed.

Electron microscopy of defects in silicon-on-insulator structures formed by selective epitaxial growth

In the interest of obtaining increased integrated circuit device density, a relatively new technology known as selective epitaxial growth (SEG) of silicon is being explored, especially for improved isolation of devices including possible three dimensional (vertical) integration. This technology involves the deposition and selective nucleation and growth of silicon from the vapor phase, seeded by the silicon substrate. The process is “selective” because nucleation and growth occurs on the silicon substrate but is prohibited on the oxide. The epitaxial silicon proceeds to grow upward and laterally over the oxide.Silicon deposition was performed in a horizontal hot-walled low pressure chemical vapor deposition (LPCVD) reactor. A dry thermal oxide was grown on the substrates, patterned, and etched to create seed windows. A 900 °C prebake was performed at a pressure of 6 torr in a hydrogen ambient for a period of 15 minutes, with in some cases, a small concentration (approximately 0.025%) of dichlorosilane (DCS) gas, and deposition was performed at 850 °C through the decomposition of DCS gas: SiH2Cl2 -> Si(s)+ 2HCl(g).

Silicon monolayer growth using dichlorosilane and hydrogen in a near atmospheric pressure chemical vapor deposition reactor

Monolayer growth of silicon in a chemical vapor deposition reactor has been investigated in the dichlorosilane (DCS)-hydrogen system. During each deposition cycle the wafer is rotated through the separate DCS and hydrogen streams. A 1 monolayer cycle -1 plateau in the growth rate was obtained over a fourfold increase in the DCS partial pressure, resulting in a 0.48 μm h -1 deposition rate. The experiments were conducted at 825°C and 50 Torr. The effects of reactant partial pressures and cycle time on the deposition will be discussed, as well as possible mechanisms for this process.

The Influence of Temperature Gradients on Partial Pressures in a Cvd Reactor

AbstractThe influence of temperature gradients on the partial pressures of a binary mixture in a cold wall low pressure chemical vapor deposition reactor was determined by Raman spectroscopy of the gaseous species in the reactor. It is demonstrated for the first time that the partial pressure of the heavy constituent in the hot region of a low pressure reactor is reduced by 35 % due to the Soret effect. Model calculations that included the Soret effect are in agreement with the experimental data.

Influence of Flow Dynamics on The Morphology of CVD Aluminum Thin Films

AbstractAluminum thin films were deposited by chemical vapor deposition on SiO2 substrates using trimethylamine alane (TMAA) in a low pressure CVD reactor system. A high TMAA flow rate during deposition, combined with an initial burst of added argon during the nucleation of the substrate surface resulted in the growth of aluminum thin films with excellent purity and surface morphologies. Film resistivities averaged 3.4 μΩ-cm, and the average surface peak-to-valley height for each film was found to be <4% of the film thickness. The surfaces of films with thicknesses of ≤ 1 μm were extremely smooth and reflective. In contrast, the use of a high alane flow rate in the absence of any added argon resulted in the growth of films with extremely textured surface morphologies. Furthermore, films grown using an argon carrier gas, but with a slow alane flow rate, exhibited both textured surface morphologies and whisker growth.

Surface-sensitive multiple internal reflection spectroscopy as a tool to study surface mechanisms in CVD: the example of UV photodeposition of silicon dioxide and silicon nitride

Multiple internal reflection-absorption spectroscopy is used here in situ in a low pressure CVD reactor, in order to demonstrate its potential as a surface analysis tool with a sensitivity well below monolayer coverages in many growth and deposition configurations. Two examples of its capacity to provide evidence for new surface processes are given in the particular case of photodeposition of silicon dioxide and silicon nitride: (i) identification of the molecular configuration associated to the photochemisorbed silane site on the Si 3N 4 photodeposition front in the SiH 4/NH 3 system, in a case where its infrared signature is buried in a large contribution from bulk species; (ii) evidence for the oxidization of silicon hydride and dihydride species by photoexcited N 2O in the UVCVD of SiO 2 in the SiH 4/N 2O precursor system. Such a reaction could be expected to occur from standard chemical knowledge, but deposited films analyzed ex situ did not offer any evidence for it in the form of water and silanol groups incorporated into the films.

Low pressure chemical vapor deposition of massive Si 1- xGe x gradient crystals and applications in short-wavelength diffraction

Bragg reflection from single crystals is commonly applied to define monochromatic beams in neutron and X-ray scattering. In general, mosaic crystals provide a significantly higher particle flux than perfect crystals, at the expense of a deterioration in the beam divergence. This disadvantage can be overcome by using gradient crystals, which are characterized by a continuous variation in the crystal lattice spacing. Diffraction from a gradient crystal can be described by simple mirror reflection for a desired wavelength band. We synthesized various Si 1- x Ge x single crystals with both fixed and continuously varying concentrations. They were grown on silicon substrates from a mixture of SiH 4, GeH 4, H 2, HCl in a low pressure chemical vapor deposition reactor. The lattice spacing gradient was obtained by controlled variation of the gas flows. The various characterization techniques employed emphasize in particular the aspects of growth rate, crystallinity and mixing of the components, A test on a neutron diffractometer of a 0.85 mm thick crystal, grown for 24 h, showed the expected performance.

Analysis of Transition Regime Flows in Low Pressure Chemical Vapor Deposition Reactors Using the Direct Simulation Monte Carlo Method

The direct simulation Monte Carlo method has been used to simulate transition regime flows in a horizontal multiple‐wafer low pressure chemical vapor deposition (LPCVD) reactor. Both the region between two wafers and a long section of the entire LPCVD reactor tube were investigated. In the interwafer simulations, a binary mixture consisting of a representative reactant molecule and was used as a model system and the reactive sticking coefficient, configuration of wafers and gas composition were varied to determine their effects on growth rate uniformity. Additionally, a comparison was made with a continuum‐based analytical model where the effective diffusion coefficient in the transition regime was determined and the importance of gas‐surface interactions was established. In the multi‐wafer simulations, the pressure drop and residence time distribution were determined for various wafer configurations and entering gas conditions with the bulk of the pressure drop occurring across the wafers as the molecules resided primarily in the upstream region. The distribution of species for gas mixtures was largely governed by diffusive effects with evidence of species separation occurring by means of pressure diffusion. For reactive gas flows, nonuniformity effects persisted in the simulations for reaction probabilities greater than 0.01.

X-ray Photoelectron Study of TiN

Thin films of TiN were deposited from TiCl4, NH3, and H2 in a lamp heated single wafer “warm wall” low pressure chemical vapor deposition reactor. The deposition was carried out on a TiSi2/Si sample. The thickness of the films is estimated to be 100 nm. The films were analyzed by x-ray diffraction, Rutherford backscattering spectroscopy, and x-ray photoelectron spectroscopy. The XPS data in Ti 2p, N 1s, Ti L3M23V, and Ti L3M23M23 regions are presented.

Silicon nitride films deposited from SiH 2Cl 2NH 3 by low pressure chemical vapor deposition: kinetics, thermodynamics, composition and structure

The growth of stoichiometric and non-stoichiometric silicon nitride films was studied experimentally on 100 mm silicon wafers by batch depositions from the dichlorosilane (SiH 2Cl 2)-ammonia (NH 3) system in a hot-wall horizontal low pressure chemical vapor deposition (LPCVD) reactor. The growth kinetics were discussed in terms of the Langmuir adsorption isotherm. The kinetic parameters were determined by comparing the experimental data with a one-dimensional simulation model. The decomposition of NH 3 at high temperatures was included in the simulation procedure. When the SiH 2Cl 2:NH 3 ratios were greater than 1.5, a quantity higher than the thermodynamic critical values above which Si-rich nitride films begin to deposit, various SiN x films with x < 4 3 were obtained. The composition of the SiN x films was found to vary along the LPCVD reactor. The film stoichiometry was examined by Rutherford backscattering and ellipsometry measurements. According to kinetic and thermodynamic studies, the pyrolysis of dichlorosilane at elevated temperatures (> 700 °C) is the cause for the deposition of Si-rich nitride films. Furthermore, two types of deposited SiN x films were observed; one type showed a typical film density around 3.70 g cm −3 while the other type exhibited a remarkably lower film density below 3.50 g cm −3.