Simulation And Design Of Temperature Field In GaN-MOCVD With The Infrared Heating System

MOCVD (Metal-organic Chemical Vapor Deposition), is a key technology in the manufacturing of semiconductor materials and devices, especially in the GaN-based optical and microwave power devices. The temperature field uniformity of the reaction chamber, as the core component of MOCVD, directly influences the quality and properties of materials. Under the limited cost, the MOCVD model is simulated and designed in computer, which can provide a great help to design and improve actual equipments. In this paper, using the finite element simulation software COMSOL Multiphysics, the temperature field on the MOCVD reaction model with infrared heating system is simulated and analyzed. The major achievements of this paper are as follows:(1) The two-dimensional ax symmetric reaction chamber of the MOCVD heated by infrared mode is established. After the analysis and comparison of filament heating mode and flake heating mode, the results are as follows:firstly, the flake heating mode has a higher efficiency than the filament heating mode; secondly, the heater should appropriately extend to the graphite plate.(2) A method to determine multiple heater location is presented. The simulation shows that, the outer heater has a greater heating power per unit volume than the inner ring in the multiple heaters system.(3) A concept, modulate curve of heaters, and its approximate characterization method is provided. And from the heating power, the position and the width size of the heater, the change of the peak point of the curve is studied, and a reasonable explanation is given. The study shows that:in the conditions permit, the outer heater width should be small or appropriately extend to the graphite plate, to reduce the influence of edge effect.(4) Analysis and comparison of heating rate of four inch wafers on the graphite plate with and without SiC coating conditions; analysis and comparison of the surface temperature uniformity of four inch wafers on the graphite plate with and without baked conditions. The results show that, in the graphite plate material design, it can improve the epitaxial growth uniformity to coat the similar materials with the growth material near the wafer pocket; To have a high emissivity coating is beneficial to improve the graphite plate heat exchange efficiency of the graphite plate in order to achieve rapid heating and cooling purposes.(5) Based on eight inch graphite plate with common Rim structure, with the wafer deformation considered, the improved-Rim structure is put forward and its Rim depth should be below2mm in the actual condition. The improved-Rimmed pocket makes the eight inch wafer within0.5K under a ideally conditions. And its design is more flexible; it can increase or decrease the thermal compensation of the edge through changing the number of the point (line) on the rim ring. Improved-Rim structure has thermal stability.