4H-SiC同质外延生长 Grove模型研究

摘要

本文通过对4H-SiC同质外延化学反应和生长条件的分析，建立了4H-SiC同质外延生长的Grove模型，并结合实验结果进行了分析和验证。通过理论分析和实验验证，得到了外延中氢气载气流量和生长温度对4H-SiC同质外延生长速率的影响。研究表明：外延生长速率在衬底直径上为碗型分布，中心的生长速率略低于边缘的生长速率；随着载气流量的增大，生长速率由输运控制转变为反应速率控制，生长速率先增大而后逐渐降低；载气流量的增加，会使高温区会发生漂移，生长速率的理论值和实验出现一定的偏移；随着外延生长温度的升高，化学反应速率和气相转移系数都会增大，提高了外延速率；温度对外延反应速率的影响远大于对生长质量输运的影响，当温度过分升高后，外延生长会进入质量控制区；但过高的生长温度导致源气体在生长区边缘发生反应，生成固体粒子，使实际参与外延生长的粒子数减少，降低了生长速率，且固体粒子会有一定的概率落在外延层上，严重影响外延层的质量。通过调节氢气流量，衬底旋转速度和生长温度，可以有效的控制外延的生长速度和厚度的均匀性。%In this paper, A Grove model on the homoepitaxial growth of 4H-SiC is presented, based on the structure and growth conditions of CVD system. According to the model analysis, the growth rate of 4H-SiC is quiet influenced by carrier gas flow rate and temperature, which is verified by experiments. Growth rate along the substrate has a bowl-shaped distribution, and the growth rate on the center is slightly lower than on the edge. As the carrier gas flow rate increases, the growth rate controlled by the transport changes into the reaction rate control, the growth rate first increases and then decreases. The position of highest temperature in the actor will be drifted with the carrier gas flow increasing. The reaction rate and the mass transport coefficient increase with the rise of growth temperature, which can cause the increase of growth rate. But the effect of temperature on reaction rate is much greater than on the mass transport. When the temperature rises excessively, the epitaxial growth will be determined by the mass transport. But the high reaction temperature results in forming some particles at the edge of reactor, which can reduce the growth rate, and the particles will have a chance to fall on the epitaxial layer, thus seriously affecting the quality of the epitaxial layer. All the above shows that the growth rate and thickness uniformity can effectively controlled by adjusting the flow rate of hydrogen, the rotational speed of the substrate and the growth temperature.