Modeling of the elementary gas‐phase reaction during chemical vapor deposition of silicon carbide from CH 3 SiCl 3 /H 2

Funato

Int J of Chemical Kinetics

et al. 2021

Self Cite

We established a kinetic model (the UT2017 model) for chemical vapor deposition of silicon carbide (SiC) from methyltrichlorosilane (CH3SiCl3, MTS)/H2, and quantitatively identified CH2SiCl3 as one of the SiC film‐forming species. In a previous study, we established a kinetic model (the UT2014 model), which reproduced the overall decomposition of MTS, but had not validated it in terms of radicals. In the present study, we first validated the UT2014 model by comparing it with the experimental results of radical production from MTS by Lemieux et al, without H2 present. The UT2014 model did not reproduce the production of CH2Cl from MTS at 1247°C. We found that the reactions of CH2SiCl3 isomerization to CH2ClSiCl2 and CH2ClSiCl2 decomposition to CH2Cl and SiCl2 were important for the production of CH2Cl from MTS. We re‐calculated those constants in pressure‐dependent formulas using the Rice‐Ramsperger‐Kassel‐Marcus method at the CBS‐QB3 level. These chemistries were added to the UT2014 model to yield the UT2017 model, which reproduced the production of radicals, including CH2Cl. Finally, using the UT2017 model, we simulated the gas composition under typical SiC chemical vapor infiltration conditions, which comprised mainly MTS and H2. A comparison of the simulation results with the partial pressure of film‐forming species in our previous report suggested that CH2SiCl3 was the possible film‐forming species of SiC from MTS/H2. For quantitative verification, we estimated the distribution of the partial pressure of CH2SiCl3 in our reactor while considering the consumption of CH2SiCl3 on the SiC surface. The values from this simulation result were almost identical to our experimental results for all positions in the reactor. Thus, we showed quantitatively that CH2SiCl3 is the film‐forming species of SiC.

Section: Introductionmentioning

confidence: 82%

Section: Gas‐phase Kinetic Simulation Under Typical Sic CVI Conditionmentioning

confidence: 99%

Elementary gas‐phase reactions of radical species during chemical vapor deposition of silicon carbide using CH₃SiCl₃

Funato

Int J of Chemical Kinetics

et al. 2021

Self Cite

“…For SiC-CVD from MTS/H 2 , the partial pressures of gas-phase species as a function of residence time were calculated via elementary reaction simulation using CHEMKIN-PRO, based on our developed UT2017 model. 27,28 3. FUNDAMENTALS: KINETIC STUDY ON CONTINUOUS FILM FORMATION OF SIC-CVD In this chapter, the surface reactions of SiC-CVD at the continuous film formation stage are discussed, where the number, η, and C of the film-forming species, were extracted experimentally.…”

Section: Methodsmentioning

confidence: 99%

“…Figure 8 shows the time-evolutional P of various gas-phase species calculated via the gas-phase elementary reaction simulation during SiC-CVD from MTS/H 2 , at T = 900 and 1000 °C, using our developed UT2017 model. 27,28 T profiles in the reactor are shown as dashed lines. The calculation does not include the deposition reaction of SiC on the surface, but is sufficient to determine the approximate C in the gas phase.…”

Section: Stoichiometric Composition Of Sic At the Initial Stage Of Cv...mentioning

confidence: 99%

Conformal and Stoichiometric Chemical Vapor Deposition of Silicon Carbide onto Ultradeep Heterogeneous Micropores by Controlling the Initial Nucleation Stage

Otaka

ACS Appl. Mater. Interfaces

et al. 2021

Self Cite

Conformal chemical vapor deposition (CVD) of silicon carbide (SiC) from methyltrichlorosilane (MTS) and hydrogen (H2) onto high-aspect-ratio (HAR; typically >100:1) three-dimensional features has been a challenge in the fabrication of ceramic matrix composites. In this study, the impact of heterogeneous underlayers on the initial nucleation of SiC-CVD was studied using HAR (1000:1) microchannels with a tailored wetting underlayer of Si(100) and dewetting underlayers of thermally formed amorphous silicon dioxide (a-SiO2) and turbostratic boron nitride (t-BN). Incubation periods were distributed in the microchannels on a-SiO2 and t-BN underlayers, with the longest period of 70 min found at the feature-bottom due to a decreased concentration (C) of film-forming species. The longer incubation periods with more dewetting underlayers arose due to demoted initial nucleation. Prolonged incubation at the feature bottom led to poor conformality because thick films had already formed at the inlet when film formation began at the feature bottom. The incubation periods were eliminated by increasing the supply of MTS/H2, in accordance with classical heterogeneous nucleation theory. In the meantime, carbon-rich SiC films formed in the vicinity of dewetting a-SiO2 and t-BN underlayers at the feature bottoms, with greater carbon segregation on more dewetting underlayers. This was probably due to the deposition of pyrocarbons (CH4, C2H2, and/or C2H4) generated from MTS/H2 in the gas phase. Decreasing the temperature (T) from 1000 to 900 °C prevented carbon-rich film formation, and the expected deposition rate of pyrocarbon decreased to 0.6% for the case of CH4. A higher C of MTS/H2 combined with a lower T enabled conformal and stoichiometric film formation on the heterogeneous HAR features.

“…The calculated reaction rate constants are summarized in Table 1. The UT2019 model was devised by adding these data to the UT2017 model 20,21 …”

Section: Establishing the Reaction Model Of The Formation Of Chlorina...mentioning

confidence: 99%

Identifying the mechanism of formation of chlorinated silane polymer by‐products during chemical vapor infiltration of SiC from CH₃SiCl₃/H₂

Fukushima

Int J of Chemical Kinetics

et al. 2022

Self Cite

Polymerization by‐products with the formula (SiCl2)n or SinHxCl2n–x are accumulated at the reactor exhaust of SiC chemical vapor infiltration (CVI) from CH3SiCl3/H2, which occur as an explosive hazard. Thermodynamic constants of the chlorinated silane polymers (SiCl2)n and Cl(SiCl2)mCl (n ≤ 5, m ≤ 4) were obtained by quantum chemical calculations using the CBS‐QB3 method. Polymerization reaction pathways of SiCl2 to (SiCl2)n and Cl(SiCl2)mCl (n ≤ 3, m ≤ 3) were also determined using the CBS‐QB3 method, with higher accuracy than in previous reports. The thermodynamic and kinetic constants were incorporated into an existing elementary reaction model of CH3SiCl3 (methyltrichlorosilane; MTS) reacting with H2 to derive the UT2019 model. This enabled the decomposition of MTS into SiCl2 to be studied. Chemical equilibrium calculations and gas‐phase kinetic simulations were performed. The chemical equilibrium calculations revealed that the chlorinated silane polymers, which are explosive by‐products of CVI of SiC, are unstable in the gas phase at any temperature under reduced pressure conditions, suggesting that their formation could be inhibited by controlling the gas‐phase reactions. The gas‐phase kinetic simulations showed that by‐products with a polymerization degree of 3 are not produced above 400°C, but are rapidly produced in the gas phase below 400°C. These findings also apply to the chemical vapor deposition of Si from chlorinated silane precursors.