Thermodynamic design of a high temperature chemical vapor deposition process to synthesize α-SiC in Si-C-H and Si-C-H-Cl systems

Computational thermodynamic study of SiC chemical vapor deposition from MTS‐H2*

“…The thermodynamic data used in this work were taken from two recently updated databases-the Scientific Group Thermodata Europe (SGTE) Substances Database (version 6, SSUB6) 55 for the gas species and the Si-C database 56 for condensed phases. In SSUB6, there are 5746 substances (3188 condensed phase and 2558 gaseous species) within a chemical framework of 99 elements, in which 109 gas species are related to the MTS-H 2 system, more than databases used in previous work, 18,46,47 except Ref. 48.…”

“…Thus, it is widely used within functional and structural materials in high temperature, aerospace, nuclear energy, and other applications 5‐9 . Chemical vapor deposition (CVD) and infiltration (CVI) are among the most feasible and widely studied SiC fabrication approaches because of their ability to handle complex geometry, flexible processing conditions, and the high purity, high density, and excellent crystalline morphology of the prepared SiC 10‐20 . Methyltrichlorosilane (CH 3 SiCl 3 , MTS) is the most commonly used gas precursor for CVD and CVI of SiC 15‐18,21‐24 owing to its equivalent ratio of silicon (Si) to carbon (C) and the wide range of allowable deposition temperatures.…”

“…[5][6][7][8][9] Chemical vapor deposition (CVD) and infiltration (CVI) are among the most feasible and widely studied SiC fabrication approaches because of their ability to handle complex geometry, flexible processing conditions, and the high purity, high density, and excellent crystalline morphology of the prepared SiC. [10][11][12][13][14][15][16][17][18][19][20] Methyltrichlorosilane (CH 3 SiCl 3 , MTS) is the most commonly used gas precursor for CVD and CVI of SiC [15][16][17][18][21][22][23][24] owing to its equivalent ratio of silicon (Si) to carbon (C) and the wide range of allowable deposition temperatures. Hydrogen (H 2 ) is frequently used as the carrier and diluent gas with MTS, both delivering the MTS precursor to the reactor and regulating the concentration of mixed gas precursors.…”

“…46 However, the work by Deng et al 48 only focused on the condensed phases and ignored the gas species. Recently, Kang et al 18 performed thermodynamic analysis on the Si-C-H-Cl system using various Si-and C-containing precursors, including MTS. A thermodynamic database containing 66 gas, two liquid and five solid species were adopted to investigate the CVD process at 1500 ~ 3000°C, 101 325 Pa, and C/Si and Cl/Si ratios of 0 ~ 10.…”

“…First, the theoretical H 2 /MTS ratios allowing the co-deposition of free Si and SiC are significantly higher than those determined by experiments, that is, >~10 4 by thermodynamic calculations 46,48 vs. usually <100 in experiments. 28,32,[34][35][36] Second, pure SiC was prepared by CVD with H 2 /MTS ratios of around 10, 25,28,40,44,50 however, thermodynamic calculations 18,46,48,51 indicated that co-deposition of graphite and SiC should always occur at such a low ratio. It is generally accepted that the former discrepancy can be qualitatively attributed to the kinetics effects.…”