Impacts of Hot Wall CVD Process Conditions on Thickness Uniformity of 8-Inch SiC Epitaxial Layer

doi:10.16553/j.cnki.issn1000-985x.2025.0066

Abstract

Abstract: A mathematical model considering substrate rotation， Si-C-Cl-H system reaction mechanism and multi-physical heat and mass transport process were established for a typical 8-inch hot-wall horizontal SiC epitaxial growth system， and it was used for three-dimensional numerical simulation research. In particular， the effects of different substrate surface average temperature， inlet flow rate， and inlet Si/H₂ ratio on the growth rate and thickness uniformity of epitaxial layer were studied. The results show that the substrate rotation improves the uniformity of temperature distribution on the substrate surface， and the instantaneous growth rate of SiC is mainly affected by the concentration of growth components near the surface. The thickness uniformity of epitaxial layer is mainly affected by the distribution of the instantaneous growth rate of SiC along the flow direction. The instantaneous growth rate of leading edge and trailing edge of substrate must compensate each other to improve the thickness uniformity. Increasing the average temperature of substrate surface， reducing the inlet flow rate and decreasing the Si/H₂ ratio of the inlet gas all lead to change of distribution of the instantaneous growth rate along the flow direction from concave to convex， and the distribution of the actual growth rate on substrate surface gradually changes from the edge low center high to the edge high center low. The inlet flow rate has the greatest influence on the instantaneous growth rate distribution in the parameter range investigated.

Key words: silicon carbide; epitaxy; chemical vapor deposition; heat-mass transport; numerical model

CLC Number:

TQ163⁺.4

LU Runlin, ZHENG Lili, ZHANG Hui, WANG Rensong, HU Dongli. Impacts of Hot Wall CVD Process Conditions on Thickness Uniformity of 8-Inch SiC Epitaxial Layer[J]. Journal of Synthetic Crystals, 2025, 54(9): 1509-1524.

Figures/Tables 20

Fig.1 Schematic diagram of the epitaxial system. （a） Longitudinal x-z section；（b） y-z section of hot zone structure；（c） x-y section of the reaction chamber

Fig.2 Schematic diagram of the computational domain and boundary conditions of the epitaxial system （not to scale）. Only the x-z section of the three-dimensional computational domain is presented

Table 1 Thermophysical of materials used in simulations， with temperature T in K unit

Parameter	Material	Value
Density/ （kg·m^-3）	Susceptor^［16］	1 740
	Insulation^［17］	170
	Quartz glass^［18-19］	2 200
Thermal conductivity/ （W·m^-1·K^-1）	Susceptor^［16］	128.595-0.126 895T+6.884 01×10^-5T²-1.799 46×10^-8T³+1.791 50×10^-12T⁴
	Insulation^［17］	-0.067 92+0.177 2exp（3.348×10^-12T）+0.135 5exp（9.048×10^-4T）
	Quartz glass^［20］	-0.985 470+0.018 209 1T-5.290 51×10^-5T²+7.552 53×10^-8T³-5.008 12×10^-11T⁴+1.311 32×10^-14T⁵
Heat capacity/ （J·kg^-1·K^-1）	Susceptor^［16］	-159.879+3.655 02T-2.380 56×10^-3T²+7.382 78×10^-7T³-8.797 87×10^-11T⁴
	Insulation^［17］	600
	Quartz glass^［21］	931.7+0.256T-5.90×10⁷/T²

Fig.3 Distributions of temperature on the lower surface of reaction chamber with substrate rotation speed of 0 （a） and 50 r/min （b）， and gas flows from left to right

Fig.4 Mole fraction versus susceptor coordinate along the center line of the lower surface of reaction chamber. （a） C-H species and organosilicon species；（b） Si-H-Cl species

Fig.5 Temperature and mole fraction of growth species versus susceptor coordinate along the center line of the lower surface of the reaction chamber （solid line） and a plane 11 mm above the lower surface （dashed line）， including temperature （a）， mole fraction of C2H2 （b）， mole fraction of SiCl （c）， mole fraction of Si （d）

Fig.6 Instantaneous growth rate distribution in the reaction zone in the baseline case （unit： μm·h-1）. （a） Lower surface of the reaction zone；（b） upper surface of the reaction zone， and gas flows from left to right

Fig.7 Instantaneous growth rate （a） and temperature （b） change along the flow direction at the lower surface （solid line） and the upper surface （dotted line） of the reaction chamber

Fig.8 Schematic diagram of the rotating substrate

Fig.9 Distribution of instantaneous and actual growth rate versus radial coordinate. （a） Instantaneous growth rate of θ=0° （solid line）， θ=180°（dash line） and their average value （dash-dot line）；（b） the actual growth rate （solid line） and its approximation （dotted line）

Table 2 Range of operating conditions in parametric analyses

Operating condition	Range
Growth temperature/K	1 823~2 023
Gas flow rate/slm	50~150
Si/H₂ ratio/%	0.05~0.15

Fig.10 For growth temperatures of 1 823 （circle）， 1 923 （triangle） and 2 023 K （square）， temperature and mole fraction along the flow direction at the center line of the lower surface of the reaction chamber （solid line） and a plane 11 mm above the lower surface （dashed line）， including temperature （a）， mole fraction of C2H2 （b）， mole fraction of SiCl （c）， and mole fraction of Si （d）

Fig.11 For growth temperatures of 1 823 （circle）， 1 923 （triangle） and 2 023 K （square），（a） the instantaneous growth rate along the flow direction，（b） the normalized actual growth rate （solid line） and its approximation （dotted line） along the radial direction of the substrate

Fig.12 Influence of growth temperatures on the average growth rate （circle） and the non-uniformity of growth rate distribution （triangle）

Fig.13 For inlet flow rates of 50 （circle）， 100 （triangle） and 150 slm （square）， temperature and mole fraction along the flow direction at the center line of the lower surface of the reaction chamber （solid line） and a plane 11 mm above the lower surface （dashed line）， including temperature （a）， mole fraction of C2H2 （b）， mole fraction of SiCl （c）， and mole fraction of Si （d）

Fig.14 For inlet flow rates of 50 （circle）， 100 （triangle） and 150 slm （square）， the instantaneous growth rate along the flow direction （a），the normalized actual growth rate （solid line） and its approximation （dotted line） along the radial direction of the substrate （b）

Fig.15 Influences of gas flow rates on average growth rate （circle） and non-uniformity of growth rate distribution （triangle）

Fig.16 For inlet Si/H2 ratio of 0.05% （circle）， 0.15% （triangle） and 0.25% （square）， temperature and mole fraction along the flow direction at the center line of the lower surface of the reaction chamber （solid line） and a plane 11 mm above the lower surface （dashed line）， including temperature （a）， mole fraction of C2H2 （b）， mole fraction of SiCl （c）， and mole fraction of Si （d）

Fig.17 For inlet Si/H2 ratio of 0.05% （circle）， 0.15% （triangle） and 0.25% （square）， the instantaneous growth rate along the flow direction （a）， the normalized actual growth rate （solid line） and its approximation （dotted line） along the radial direction of the substrate （b）

Fig.18 Influence of Si/H2 ratio on the average growth rate （circle） and the non-uniformity of growth rate distribution （triangle）

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