Deposited Silicon Carbide Research Articles

SiC-CVD 공정에서 CFD 시뮬레이션의 응용

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

Silicon Carbide Oxidation in High‐Pressure Steam

Silicon carbide is a candidate cladding for fission power reactors that can potentially provide better accident tolerance than zirconium alloys. SiC has also been discussed as a host matrix for nuclear fuel. Chemical vapor–deposited silicon carbide specimens were exposed in 0.34–2.07 MPa steam at low gas velocity (~50 cm/min) and temperatures from 1000°C to 1300°C for 2–48 h. As previously observed at lower steam pressure of 0.15 MPa, a two‐layer SiO2 scale was formed during exposure to these conditions, composed of a porous cristobalite layer above a thin, dense amorphous SiO2 surface layer. Growth of both layers depends on temperature, time, and steam pressure. A quantitative kinetics model is presented to describe the SiO2 scale growth, whereby the amorphous layer is formed through a diffusion process and linearly consumed by an amorphous to crystalline phase transition process. Paralinear kinetics of SiC recession were observed after exposure in 0.34 MPa steam at 1200°C within 48 h. High‐pressure steam environments are seen to form very thick (10–100 μm) cristobalite SiO2 layers on CVD SiC even after relatively short‐term exposures (several hours). The crystalline SiO2 layer and SiC recession rate significantly depend on steam pressure. Another model is presented to describe the SiC recession rate in terms of steam pressure when a linear phase transition kl governing the recession kinetics, whereby the reciprocal of recession rate is found to follow a negative unity steam pressure power law.

Multiscale Analysis on Gas Phase and Surface Chemistry of SiC-CVD Process from CH3SiCl3/H2

A multi-scale analysis, which is a macro and a micro-scale analysis, was performed on the chemical vapor deposition (CVD) for the synthesis of silicon carbide (SiC) from mono-methyl tri-chlorosilane (MTS:CH3SiCl3) and H2 to elucidate the major reaction mechanism and kinetics. The multi-scale analysis provides two well-defined reaction fields, corresponding to centimeter and sub-micron characteristic length scales, respectively. From the macro-scale analysis, a detail of the kinetics on the SiC deposition was successfully investigated with different residence time. The microcavity method as a micro-scale analysis was utilized to study a chemical reaction path, and to estimate the sticking probability of growth species on the surface reaction. In order to guess a molecular of growth species on the surface reaction, a quadrupole mass spectrometry (QMS) and an elementary reaction simulation were used. These combinations of analyses revealed an overall picture of the reaction scheme of SiC-CVD.

Analysis of SiC Deposition Rate in a Tubular Hot-Wall Reactor with Polymeric Source Using the DoE Method

Atmospheric-pressure chemical vapor deposition of silicon carbide in a tubular hot-wall reactor using a polymeric source was studied. A three-dimensional model of the reactor was solved numerically based on the finite-volume method. To achieve the best desired conditions, the effects of substrate temperature, mass fraction of polycarbosilane (–Si[CH3]2–), inlet velocity, and substrate location on the SiC deposition rate were considered. These effects were investigated to obtain the optimum conditions by using the design of experiments (DoE) method. Finally, several contours are presented to help designers find suitable reactor conditions for higher performance.

Multi-Scale Analysis and Elementary Reaction Simulation of SiC-CVD Using CH3SiCl3/H2: I. Effect of Reaction Temperature

Silicon carbide (SiC) films were prepared from methyltrichlorosilane (MTS) and H2 at temperatures ranging from 900 to 1000°C by low-pressure chemical vapor deposition (CVD). Multi-scale analysis was performed on the SiC film growth rate using a growth rate profile for a tubular reactor that was 300 mm long from the inlet to the outlet and a step coverage (SC) profile for micron-sized trenches. The precursor consumption ratio was estimated using a quadrupole mass spectrometer (QMS). These systematic analyses revealed that MTS was not the direct growth species for SiC deposition. We concluded that there were two major growth species controlling the SiC deposition rate. The partial pressures of these species were estimated by SC and growth rate analyses. An elementary reaction simulation was performed to predict the SiC film growth species. A comparison between the elementary reaction simulation results and the multi-scale analysis suggested several chemical species as candidates for the direct growth species. The candidates for the first species, with a low sticking probability of around 10−3, were CH4, C2H4, and C2H2, and candidates for the second species, with a high sticking probability of around 10−1, were CH3, C2H3, and C2H5.

PH localization: a case study during electrophoretic deposition of ternary MAX phase carbide-Ti<sub>3</sub>SiC<sub>2</sub>

The pH localization phenomenon during electrophoretic deposition (EPD) of the MAX phase-Titanium silicon carbide (Ti3SiC2), from suspension in aqueous and mixed (water-ethanol) solvent was experimentally verified in presence of a cationic dispersant, polyethyleneimine (PEI). The local pHs at the electrodes were dependent on solid loadings of the suspensions; pH localization was pronounced at lower solid loading. Higher solid loading resulted in thicker deposits, shielding the electrode surface and hindering direct interaction of the electrode with the particles, thereby suppressing the change in local pH. Comparison of local pH at cathode during EPD from aqueous and mixed solvent revealed a delay in the attainment of isoelectric point (IEP) at the vicinity of electrode and slower deposition rate for mixed solvent. A necessity of concurrence between the IEP of the material and the local pH at the deposition electrode for a given system was established for the formation of good deposits.

Scaling of Thermal Positioning in Microscale and Nanoscale Bridge Structures

Heat transfer in a thermally positioned doubly clamped bridge is simulated to obtain a universal scaling for the behavior of microscale and nanoscale bridge structures over a range of dimensions, materials, ambient heat transfer conditions, and heat loads. The simulations use both free molecular and continuum models to define the heat transfer coefficient, h. Two systems are compared: one doubly clamped beam with a length of 100 μm, a width of 10 μm, and a thickness of 3 μm, and a second beam with a length of 10 μm, a width of 1 μm, and a thickness of 300 nm, in the air at a pressure from 0.01 Pa to 2 MPa. The simulations are performed for three materials: crystalline silicon, silicon carbide, and chemical vapor deposition (CVD) diamond. The numerical results show that the displacement and the response of thermally positioned nanoscale devices are strongly influenced by ambient cooling. The displacement depends on the material properties, the geometry of the beam, and the heat transfer coefficient. These results can be collapsed into a single dimensionless center displacement, δ* = δk/q″αl2, which depends on the Biot number and the system geometry. The center displacement of the system increases significantly as the bridge length increases, while these variations are negligible when the bridge width and thickness change. In the free molecular model, the center displacement varies significantly with the pressure at high Biot numbers, while it does not depend on cooling gas pressure in the continuum case. The significant variation of center displacement starts at Biot number of 0.1, which occurs at gas pressure of 27 kPa in nanoscale. As the Biot number increases, the dimensionless displacement decreases. The continuum-level effects are scaled with the statistical mechanics effects. Comparison of the dimensionless displacement with the thermal vibration in the system shows that CVD diamond systems may have displacements that are at the level of the thermal noise, while silicon carbide systems will have a higher displacement ratios.

Investigation of silicon/glass anodic bonding with PECVD silicon carbide as the intermediate layer

This paper describes the study of the conventional silicon/glass anodic bonding with plasma enhanced chemical vapor deposited silicon carbide (PE-SiC) as the intermediate layer, in order to evaluate the feasibilities of applying PE-SiC as the device's passivation layer prior to the packaging bonding and construction layer based on the bond-and-transfer technique. It is found that the mechanism of this bonding is similar to the traditional anodic bonding. As the PE-SiC thickened, the bond strength declined; meanwhile, the leak rate remained at the same level with the silicon/glass bonding. Further experiments revealed that the bonding increased the interlayer's tensile stress by 70.7 MPa and diminished the stress gradient by 24.6 MPa µm−1.

Transient stages during the chemical vapour deposition of silicon carbide from CH3SiCl3/H2: impact on the physicochemical and interfacial properties of the coatings

Transient chemical vapour deposition experiments were produced from MTS/H2 mixtures by varying the deposition temperature or the gas flow rates (QMTS or QH2) versus time. The gas phase, deposition rates and properties of the transient coating (φTr) were investigated and adhesion assessments of SiC/φTr/SiC bilayers were performed by scratch testing. Transient stages resulting from a decrease of QMTS or temperature lead to silicon co-deposition, but do not affect interfacial properties. Transient stages resulting from a decrease of QH2 eventually lead to carbon co-deposition. Thick and continuous carbon interlayers lead to a poor adhesion whereas thin and discontinuous layers do not.

Deposition of Silicon Carbide and Nitride‐Based Coatings by Atmospheric Plasma Spraying

In this work atmospheric plasma spraying of SiC and Si3N4 was investigated. Plasma spraying of these ceramics raises several problems since they would tend to decompose instead of melting at elevated temperatures during the process. To circumvent this problem the nonoxide ceramics were deposited as a composite powder mixed with nonoxide ceramic particles resulting in a ceramic/ceramic composite structure. Our findings were that using such a composite feedstock powder both oxidation and decomposition of the nonoxide particles could be avoided. A vitrified phase was also developed in the coating.

Nanocrystalline silicon carbide thin films by fluidised/packed bed chemical vapor deposition using a halogen-free single source

Thermal stability, vapor pressure, and binary gaseous diffusion coefficients of organosilanes were studied at temperatures in the range of 309–507 K in ambient pressure. The temperature dependence equilibrium vapor pressure (pe)T data yielded a straight line, when ln pe was plotted against the reciprocal temperature, leading to a standard enthalpy of sublimation (ΔsH°) values of 43.3 ± 0.6, 68.2 ± 0.8 and 72.4 ± 0.6 kJ mol−1 for 1,4-bis(trimethylsilyl)butadiyne (TMSBu), 1,4-bis(trimethylsilyl)benzene (TMSB), and 1,4-bis[(trimethylsilyl)-ethynyl]benzene (TMSEB) and vaporisation (ΔvH°) values of 33.9 ± 0.2 kJ mol−1, 44.3 ± 0.6 kJ mol−1, 64.5 ± 0.5 kJ mol−1, 75.8 ± 0.6 kJ mol−1, and 94.3 ± 0.4 kJ mol−1 for triphenylsilane (TPS), 1,4-bis[(trimethylsilyl)-ethynyl]benzene (TMSEB), triphenylvinylsilane (TPVS), 1,1,2,2-tetraphenyldisilane (TPDS), and 1,2-dimethyl-1,1,2,2-tetraphenyldisilane (DMTPDS), respectively. In order to find the enthalpy of formation (ΔfH°) at the condensed and gaseous state of each molecule at standard temperature, the semi-empirical quantum chemical analysis was carried out. The screened/selected ideal candidate was used to deposit silicon carbide thin films on the carbon black or silicon or zirconia particles in the fluidised/packed bed reactor. The deposits were characterized using X-ray diffraction and scanning electron microscopy methods.

A Study of Predominated Pathway of Initial Processes in Chemical Vapor Deposition of Silicon-Carbide from Methyltrichlorosilane and Hydrogen System

The initial pathways in the CVD process of preparing silicon carbides with CH3SiCl3-H2 precursors was searched theoretically, which involves 21 well-defined transition states. The geometries of the species were optimized by employing the B3PW91/6-311G(d,p) method. The energy barriers and the reaction energies were evaluated with the accurate model chemistry method at G3(MP2) level after a non-dynamical electronic correlation detection. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. The energies at any temperature could be derived classically by using the analytical heat capacities. It was found that the free radical reactions have clearly kinetic ascendency to be the most efficient decomposition pathway.

A Study of Predominated Pathway of Initial Processes in Chemical Vapor Deposition of Silicon-Carbide from Methyltrichlorosilane and Hydrogen System

The initial pathways in the CVD process of preparing silicon carbides with CH3SiCl3-H2 precursors was searched theoretically, which involves 21 well-defined transition states. The geometries of the species were optimized by employing the B3PW91/6-311G(d,p) method. The energy barriers and the reaction energies were evaluated with the accurate model chemistry method at G3(MP2) level after a non-dynamical electronic correlation detection. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. The energies at any temperature could be derived classically by using the analytical heat capacities. It was found that the free radical reactions have clearly kinetic ascendency to be the most efficient decomposition pathway.

C3H8-SiCl4-H2시스템에서 FactSage를 이용한 압력-조성-온도 3차원 상평형도의 응용

In order to deposit a homogeneous and uniform β-SiC films by chemical vapor deposition, we constructed the phase-diagram of β-SiC over graphite and silicon via computational thermodynamic calculation considering pressure(P), temperature(T) and gas composition(C) as variables in C 3 H 8 -SiCl 4 -H 2 system. During the calculation, the ratio of Cl/Si and C/Si is maintained to be 4 and 1, respectively, and H/Si ratio is varied from 2.67 to 15,000. The P-T-C diagram showed very steep phase boundary between SiC+C and SiC region perpendicular to H/Si axis and also showed SiC+Si region with very large H/Si value of ~6700. The diagram can be applied not only to the prediction of the deposited phase composition but to compositional variation due to the temperature distribution in the reactor. The P-T-C diagram could provide the better understanding of chemical vapor deposition of silicon carbide.

Multiscale Analysis of Silicon Carbide-Chemical Vapor Deposition Process

A kinetic study, which was performed by using multi-scale (a macro and a micro-scale) analysis, is presented in order to determine the reaction mechanism of the chemical vapor deposition (CVD) of silicon carbide (SiC) from CH3SiCl3 (MTS)/H2 gaseous mixture. The multi-scale analysis provides two well-defined reaction fields, corresponding to the flat substrates placed in a hot wall reactor and micro trenches on the substrate surface, with centimeter and submicron characteristic length scales, respectively. The microcavity method is a micro-scale analysis used to study the relative contributions of gas-phase and surface reactions to the SiC growth, and to determine the sticking probability of growth species in CVD reaction systems. From the macro-scale analysis, activation energy of the growth rate was estimated to be 43.0 kcal/mol at the up-stream part and the sticking probability was estimated to be 9.5 x 10(-7) at 1273 K and 6.8 x 10(-6) at 1373 K. On the other hand, we examined a sticking probability (eta) and the reaction mechanism by using the microcavity method. From the micro-scale analysis, we found that at least two growth species, a stable intermediate 1 (eta 1, = 1.3 x 10(-3) at 1273 K and 4.5 x 10(-3) at 1373 K) and a highly active intermediate 2 (eta 2 = 2.0 x 10(-1) at 1273 K and 5.4 x 10(-1) at 1373 K), are formed as byproducts of the gas-phase reaction. Activation energy of the sticking probability was 43.9 kcal/mol in the case of the intermediate 1 and 34.5 kcal/mol in the case of the intermediate 2. We could also confirm that the source precursor, MTS, was not the film growth species. Another analytical model based on Monte Carlo simulations correlates the film profile in the microcavity to the sticking probability of the deposition species. The combination of these two analysis techniques presents an overall picture of the reaction scheme.

Study of deposition patterns of plating layers in SiC/Cu composites by electro-brush plating

SiC reinforced copper composite coatings were prepared by electro-brush plating with micron-size silicon carbide (SiC) ranging from 1 to 5μm on pure copper sheet in this paper. The micro-structural characterizations of SiC/Cu composite coatings were performed by optical microscope and Scanning Electron Microscope (SEM) coupled with spectrometer, to study co-deposition mechanism of SiC/Cu. It was found that there were three different patterns of SiC deposition in plating layers during electro-brush plating process, i.e. the particles could deposit inside copper grains, in grain boundaries, or in holes of the surface. To investigate deposition mechanism of each pattern, size of SiC and copper grains was compared. By comparison of size of copper grains and hard particles, SiC were either wrapped in copper grains or deposited in grain boundaries. Moreover, electro-brush plating layers at different brush velocities and current densities were obtained respectively, to analyze the microstructure evolution of the composite coatings. The hardness of plating layers was measured. The results indicated at the current density of 3A/dm2, the SiC/Cu coating was compact with SiC content at a high level and the hardness reached a maximum.

Initial decomposition of methyltrichlorosilane in the chemical vapor deposition of silicon-carbide

All of the possible initial decomposition pathways in the CVD process of preparing silicon carbides with CH 3SiCl 3–H 2 precursors were searched theoretically. The geometries of the species were optimized with B3PW91/6-311G(d,p). The energy barriers and the reaction energies were evaluated with the accurate model chemistry at G3(MP2) level after a non-dynamical electronic correlation detection. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. Nine transition states are firstly reported in initial decomposition of MTS. Comparisons with a previous theoretical study are excellent, but additional reactions studied here are found to be relevant as well.

Contact angle measurement of molten lead–lithium on silicon carbide surfaces

Measurements of the contact angles at the different temperatures of a molten lead–lithium eutectic alloy (PbLi) droplet on a silicon carbide (SiC) wall are needed for the research and development both of a magnetic confinement fusion (MCF) and an inertia confinement fusion (ICF) blankets. PbLi coolant/breeder flows in the coolant channel, which is made of the SiC walls, and will experience a flow slip at the wall, called as a magnetohydrodynamic (MHD) slip flow. The ICF blanket adopts a molten PbLi film flow along the first wall made of SiC. The PbLi contact angle database is necessary as the thermal property for numerically predicting the behavior of the flowing molten PbLi film. This study attempts the measurement of the contact angles between the molten PbLi and the various SiC surfaces. For example, in order to examine the initial PbLi wettability, we measured the contact angles of a chemical vapor deposition (CVD) SiC, a nano-infiltration and transient eutectic-phase (NITE) SiC/SiC composites, and a NITE SiC in an inert atmosphere. We obtained the contact angle database of the molten PbLi, varying the temperature of PbLi from 250 to 400 °C, on a surface-polished as well as an unpolished SiC.

Study on the Thermoelectric Properties of CVD SiC Deposited with Inert Gases

We deposited silicon carbide (SiC) by the chemical vapor deposition (CVD) method using the inert gases Ar and He. It was confirmed that SiC deposited with inert gases had a porous microstructure and high carbon content. We also studied the thermoelectric properties. SiC deposited with He gas had lower electrical and thermal conductivity compared with SiC deposited with Ar gas. Both samples using Ar and He exhibited a negative Seebeck coefficient, indicating n-type semiconductor behavior. The calculated figure of merit (Z) of SiC deposited with inert gases was improved compared with SiC deposited with H2 or N2 gas. The value for SiC deposited with He was higher than that for SiC deposited with Ar. The thermoelectric properties of porous silicon carbide deposited with inert gases were also compared with those of silicon carbide deposited with hydrogen or nitrogen gas.

Demonstration of PECVD SiC–SiO$_{2}$–SiC Horizontal Slot Waveguides

We report on the first demonstration of guiding light in horizontal slot-waveguides using a plasma-enhanced chemical vapor deposition silicon carbide (SiC)-silicon oxide (SiO2)-SiC structure. Propagation losses of 23.9 ±1.2 dB/cm have been measured for the quasi-transverse-magnetic mode of the fabricated slot waveguides at 1.3 ?m .