压力和转速对垂直热壁CVD外延SiC生长速率和均匀性的影响

doi:10.15541/jim20260067

摘要/Abstract

摘要： 碳化硅(SiC)是制备大功率、高温高频电子器件的核心宽禁带半导体材料,其外延层质量直接关系器件的性能与可靠性。垂直热壁化学气相沉积(Chemical Vapor Deposition, CVD)因具备温度场和流场稳定、生长速率快、有助于提高厚度均匀性等优势,代表了未来SiC外延行业的重要发展方向。反应腔压力和衬底转速作为垂直热壁CVD工艺中两个关键可调参数,通过改变反应腔内流场分布、边界层厚度及前驱体浓度分布,对外延层生长速率和厚度均匀性产生显著影响。因此,本研究探究上述两个关键工艺参数对垂直热壁CVD SiC外延生长过程的影响机理,并确定兼顾高生长速率与均匀性的优化工艺窗口。基于有限体积法,建立了垂直热壁CVD SiC外延过程的传热传质数值模型,采用TCS/C₂H₄/H₂前驱体体系的气相反应和表面反应动力学。设计多组数值模拟算例,系统研究不同反应腔压力和衬底转速对外延过程的影响规律。模拟结果表明,随着反应腔压力从50 mbar(1 mbar=100 Pa)升高到450 mbar,衬底上方CH₄和SiCl₂等主要反应物浓度逐渐升高,同时组分边界层厚度减薄,外延生长速率从35 μm/h升高到65 μm/h,但当压力超过250 mbar时,腔体内流场易产生涡流,导致径向质量输运不均匀,厚度均匀性逐渐恶化。在衬底转速方面,生长速率随转速提高而逐渐上升,在0~500 r/min范围内,转速提升有效优化了径向组分浓度分布,改善了外延层厚度均匀性;而当转速超过500 r/min时,旋转效应加剧衬底边缘组分聚集,形成中心浓度高、边缘浓度低的分布,导致均匀性轻微恶化。上述结果揭示了反应腔压力与衬底转速通过调控边界层厚度和径向浓度分布影响外延生长速率和厚度均匀性的内在机理,确定了腔体压力为250 mbar,衬底转速为500 r/min的工艺参数可实现超过50 μm/h的生长速率和2.5%的厚度均匀性,为优化SiC外延生长工艺参数、推动垂直热壁CVD技术的产业化应用提供了理论依据。

关键词: 垂直热壁CVD, 碳化硅, 数值模拟, 反应腔压力, 衬底转速

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 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 50 mbar (1 mbar=100 Pa) to 450 mbar, 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 250 mbar, 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 250 mbar and a substrate rotation speed of 500 r/min can achieve a growth rate exceeding 50 μm/h and a thickness uniformity of 2.5%, 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

中图分类号:

O782

李晓磊, 齐小方, 马文成, 徐永宽. 压力和转速对垂直热壁CVD外延SiC生长速率和均匀性的影响[J]. 无机材料学报, DOI: 10.15541/jim20260067.

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, DOI: 10.15541/jim20260067.

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