大尺寸电阻加热式碳化硅晶体生长热场设计与优化

大尺寸低缺陷碳化硅(SiC)单晶体是功率器件和射频(RF)器件的重要基础材料,物理气相传输(physical vapor transport, PVT)法是目前生长大尺寸SiC单晶体的主要方法。获得大尺寸高品质晶体的核心是通过调节组分、温度、压力实现气相组分在晶体生长界面均匀定向结晶,同时尽可能减小晶体的热应力。本文对电阻加热式8英寸(1英寸=2.54 cm)碳化硅大尺寸晶体生长系统展开热场设计研究。首先建立描述碳化硅原料受热分解热质输运及其多孔结构演变、系统热输运的物理和数学模型,进而使用数值模拟方法研究加热器位置、加热器功率和辐射孔径对温度分布的影响及其规律,并优化热场结构。数值模拟结果显示,通过优化散热孔形状、保温棉的结构等设计参数,电阻加热式大尺寸晶体生长系统在晶锭厚度变化、多孔介质原料消耗的情况下均能达到较低的晶体横向温度梯度和较高的纵向温度梯度。

Thermal Field Design and Optimization of Resistance Heated Large-Size SiC Crystal Growth System

Large-size, low-defect silicon carbide single crystal is one of the most important fundamental materials for power and radio frequency (RF) devices. The physical vapor transport (PVT) method is the major technique for growing large-size SiC single crystals currently. The core to obtain large-size and high-quality crystals is to find optimal matching conditions for vapor composition, temperature, and pressure at the crystal growth interface so that the vapor can crystallize evenly, at the same time the thermal stress in crystals is sufficiently small. This paper presents the numerical studies of the thermal field design for 8 inch SiC bulk crystal growth system with resistance heating. Specifically, the influences of heater position, heating power and the radiation aperture’s diameter on thermal field were studied, in conjunction with the optimal system structure. Numerical simulation results show that optimizing design parameters such as the shape of heat dissipation hole and the structure of insulation can achieve thermal fields with low horizontal temperature gradient and high axial temperature gradient desirable for the growth of large-size SiC crystal by resistance heating system while the thickness of grown crystal changes and porous raw material is consumed.