Effects of Pressure and Rotation Speed on the Growth Rate and Uniformity of SiC in a Vertical Hot-wall CVD Epitaxial System

doi:10.15541/jim20260067

Abstract

Abstract:

Silicon carbide (SiC) is a core wide-bandgap semiconductor material used in the fabrication of high-power, high-temperature, and high-frequency electronic devices. The quality of its epitaxial layers directly affects device performance and reliability. Vertical hot-wall chemical vapor deposition (CVD) represents a key future development direction for the SiC epitaxy industry due to its advantages, including stable temperature and flow fields, fast growth rates, and improved thickness uniformity. Reaction chamber pressure and substrate rotation speed are two key adjustable parameters in the vertical hot-wall CVD process. By altering the flow field distribution, boundary layer thickness, and precursor concentration distribution within the reaction chamber, these parameters exert a significant influence on the epitaxial growth rate and thickness uniformity. Therefore, this study aims to investigate the mechanisms by which these two key process parameters affect the vertical hot-wall CVD SiC epitaxial growth process and to determine an optimized process window that balances high growth rates with uniformity. Based on the finite volume method, a numerical model for heat and mass transfer in the vertical hot-wall CVD SiC epitaxial growth process was established, incorporating the gas-phase and surface reaction kinetics of the trichlorosilane (TCS)/C₂H₄/H₂ precursor system. Multiple simulation scenarios were designed to systematically investigate the influence of different reaction chamber pressures and substrate rotation speeds on the epitaxial growth process. Simulation results indicate that as the reaction chamber pressure increases from 5 kPa to 45 kPa, the concentrations of major reactants such as CH₄ and SiCl₂ above the substrate gradually rise, while the thickness of the component boundary layer decreases, and the epitaxial growth rate increases from 35 μm/h to 65 μm/h. However, when the pressure exceeds 25 kPa, vortices tend to form in the chamber flow field, leading to non-uniform radial mass transport and a gradual deterioration in the epitaxial layer's thickness uniformity. Regarding substrate rotation speed, the growth rate increases gradually with increasing rotation speed. Within the range of 0-500 r/min, increasing the rotation speed effectively optimizes the radial concentration distribution of components and improves the thickness uniformity of the epitaxial layer; however, when the rotation speed exceeds 500 r/min, the rotational effect intensifies the aggregation of components at the substrate edges, resulting in a distribution with high concentration at the center and low concentration at the edges, which causes a slight deterioration in uniformity. The above results reveal the intrinsic mechanism by which reaction chamber pressure and substrate rotation speed influence epitaxial growth rate and thickness uniformity through the regulation of boundary layer thickness and radial concentration distribution. It was determined that a chamber pressure of 25 kPa and a substrate rotation speed of 500 r/min can achieve a growth rate exceeding 50 μm/h and a thickness uniformity of 2.0%, providing a theoretical basis for optimizing SiC epitaxial growth parameters and promoting the industrial application of vertical hot-wall CVD technology.

Key words: vertical hot-wall CVD, silicon carbide, numerical simulation, reaction pressure, substrate rotation rate

CLC Number:

O782

LI Xiaolei, QI Xiaofang, MA Wencheng, XU Yongkuan. Effects of Pressure and Rotation Speed on the Growth Rate and Uniformity of SiC in a Vertical Hot-wall CVD Epitaxial System[J]. Journal of Inorganic Materials, 2026, 41(10): 1459-1469.

Figures/Tables 15

Fig. 1 Schematic diagram of the vertical hot-wall CVD SiC epitaxial growth furnace

Table 1 Physical parameters of main materials

Material	Density/(kg·m^-3)	Specific heat/(J·kg^-1·K^-1)	Thermal conductivity/ (W·m^-1·K^-1)	Viscosity/ (kg·m^-1·s^-1)	Surface emissivity
Felt	120	200	9×10^-3+2.7×10^-4T+1.1× 10^-10T³	-	0.8
Graphite	1950	753.5lnT-3466.7	1808×T^-0.479	-	0.8
SiC	3220	1281	6.11×10⁴/(T-115)	-	0.9
H₂	Incompressible-ideal-gas	1.4×10⁴+3.4T-3.4×10^-3T²- 3.9×10^-7T³+1.7×10^-9T⁴	0.2+3.2×10^-4T	8.4×10^-6+1.1×10^-8T	-
Mixture-gas	Kinetic-theory	Kinetic-theory	Kinetic-theory	-	-

Table 2 Gas phase kinetic mechanism

Reaction	A	E_a	n
C₂H₄+H→C₂H₅	2.2×10⁸	8.64×10³	0
C₂H₅+3H→2CH₄	5.0×10¹¹	0	0
C₂H₅+2H₂→2CH₄+H	9.0×10¹³	0	0
C₂H₆+H→C₂H₅+H₂	1.4×10⁹	3.09×10⁵	0.5
C₂H₅→C₂H₄+H	1.4×10⁸	1.56×10⁵	0
SiHCl₃→SiCl₂+HCl	3.2×10¹²	7.00×10⁴	0
SiHCl₃+H₂→SiH₂Cl₂+HCl	3.2×10^-8	2.33×10⁵	0
SiH₂Cl₂→SiCl₂+H₂	2.1×10¹⁸	3.20×10⁵	0
SiH₂Cl₂→SiHCl+HCl	6.9×10¹⁴	3.17×10⁵	0
SiHCl₃+H→SiCl₃+H₂	7.4×10⁸	2.70×10³	0
SiCl₃+HCl→SiCl₄+H	1.2×10²	1.10×10⁴	0
SiHCl₃+HCl→SiCl₄+H₂	2.2×10³	4.26×10⁴	0
SiCl₄→SiCl₃+Cl	7.0×10²²	1.11×10⁴	0
C₂H₄→C₂H₂+H₂	1.5×10¹⁵	3.45×10⁴	0
SiHCl+HCl→SiCl₂+H₂	2.2×10⁸	1.00×10⁸	0.5
H+H₂→H₂	5.0×10¹¹	9.20×10⁷	-0.6

Table 3 Surface kinetic mechanism

Reaction	A	n
SiHCl₃+C_-surf→SiCl_-surf+C_-vol+H+2Cl	2.6×10¹⁶	0.5
SiCl₃+C_-surf→SiCl_-surf+C_-vol	3.2×10¹⁸	0.5
SiCl₂+C_-surf→SiCl_-surf+C_-vol+Cl	3.1×10¹⁹	0.5
SiCl₄+C_-surf→SiCl_-surf+C_-vol+3Cl	2.9×10¹⁶	0.5
SiH₂Cl₂+C_-surf→SiCl_-surf+C_-vol+2H+Cl	3.8×10⁸	0.5
SiHCl+C_-surf→Si_-surf+HCl+C_-vol	3.1×10¹⁶	0.5
SiCl_-surf→Si_-surf+Cl	2.3×10¹²	0.5
C₂H₂+2Si_-surf→2C_-surf+H₂+2Si_-vol	3.0×10¹⁸	0.5
C₂H₄+2Si_-surf→2C_-surf+2H₂+2Si_-vol	2.3×10¹⁶	0.5
CH₄+Si_-surf→C_-surf+2H₂+Si_-vol	4.3×10¹¹	0.5

Fig. 2 Temperature distribution and streamline distribution in the reaction chamber under baseline case (a) Temperature distribution; (b) Streamline distribution; (c) Flow velocity distribution. Colorful figures are available on website

Fig. 3 Distribution of molar fractions for different components in the reaction chamber under baseline case (a) CH4 molar fraction; (b) C2H2 molar fraction; (c) SiCl2 molar fraction; (d) SiCl3 molar fraction. Colorful figures are available on website

Fig. 4 Temperature and growth rate distributions on the substrate surface for baseline case

Fig. 5 Distribution of molar concentration of CH4 at different pressures (a) 5 kPa; (b) 15 kPa; (c) 25 kPa; (d) 35 kPa; (e) 45 kPa. Colorful figures are available on website

Fig. 6 Distribution of molar concentration of SiCl2 at different pressures (a) 5 kPa; (b) 15 kPa (c) 25 kPa; (d) 35 kPa; (e) 45 kPa. Colorful figures are available on website

Fig. 7 Vertical and radial distributions of CH4 molar concentration above the substrate surface at different pressures (a) Vertical distribution; (b) Radial distribution

Fig. 8 Streamline distribution at different pressures (a) 5 kPa; (b) 15 kPa; (c) 25 kPa; (d) 35 kPa; (e) 45 kPa

Fig. 9 (a) Growth rate distribution and (b) average growth rate and uniformity versus pressure

Fig. 10 Distribution of CH4 molar concentration at different rotational rates (a) 0 r/min; (b) 250 r/min; (c) 500 r/min; (d) 750 r/min; (e) 1000 r/min. Colorful figures are available on website

Fig. 11 Vertical and radial distributions of CH4 molar concentration above the substrate surface at different rotational rates (a) Vertical distribution; (b) Radial distribution

Fig. 12 (a) Growth rate distribution and (b) average growth rate and uniformity versus rotational rate

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