During the process of heteroepitaxial growth, if the lattice constant of the growing film differs from that of the substrate, the wafer surface bows, regardless of whether the lattice mismatch occurs or not. As the growth in large-scale wafers speeds up, bowing effects are becoming more and more important. Wafer bowing has a direct impact on the yield in modern mass-production compound semiconductor industries. By using finite element analysis software, the bowing deformation of the GaN wafer on sapphire substrate can be studied. This paper summarizes the causes of bowing deformation, builds the mathematical model, and deduces the relation equation of the wafer bowing. The results show that epitaxial wafer bowing has a linear relationship with the square of the diameter of the substrate but has little relationship with the thickness of the substrate. Moreover, the relation equation of the wafer bowing is also simplified finally. 1. Introduction Using MOCVD (metal-organic chemical vapor deposition) to analyze the growth of GaN-base photoelectric devices on the sapphire substrate is a common method in the semiconductor lighting industry [1–5]. In recent years, along with the unceasing enhancement of epitaxy technology and related technologies, larger sapphire substrates are needed. The optimization and improvement of MOCVD reaction chamber structure with large-scale epitaxial wafers have been studied by many domestic researchers [6–10]. Li et al. [11, 12] optimized high-frequency heating graphite base groove structure with eight-inch and twelve-inch substrates. Ying-lu et al. [13] studied the heating modulate curve of radiation heating MOCVD and proposed the design principles of the outer heater. To improve the production efficiency, some great MOCVD manufacturers also focus on how to improve and increase the MOCVD cavity and the sapphire substrate size in foreign countries. At present, two-inch and four-inch epitaxial wafers are frequently used, so manufacturers who can produce six-inch SiC and Si substrate epitaxial wafers with high quality in foreign countries would sell chips abroad [14, 15]. With the growth of the III-nitrides, sapphire becomes the most extensively used substrate material [16]. Crystals of sapphire with good quality and low price can be easily got. Besides, sapphire is stable at high temperature and the growth technology of nitrides on sapphire is now fairly mature. However, the problem of wafer bowing, which results from the difference in thermal expansion coefficient between GaN epitaxial layer and sapphire, has become much more
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