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为了研究蓝宝石/AlN/GaN外延片表面层热应力分布及影响因素,以直径d为Φ40 mm的外延片为研究对象,利用有限元分析法对其表面热应力分布进行了理论计算和仿真,验证了仿真模型的合理性。分析了外延片生长温度、蓝宝石衬底和AlN过渡层厚度对表面热应力的影响。结果显示:在1 200℃的生长温度下,外延片径向应力比轴向应力大一个量级;在径向(d<Φ32 mm)区域内的热应力分布比较均匀,热应力变化范围为±0.38%;生长温度在600~1 200℃范围内,外延层表面应力与生长温度呈近似正比关系。研究成果可为该类外延片生长工艺研究和低应力外延片的筛选标准制定提供借鉴。
In order to study the thermal stress distribution and its influencing factors on the sapphire / AlN / GaN epitaxial wafers, taking the epitaxial wafer with the diameter d of Φ40 mm as the research object, the surface thermal stress distribution of the sapphire / AlN / GaN epitaxial wafers has been theoretically calculated and simulated by finite element analysis The rationality of the simulation model. The influence of the growth temperature of epitaxial wafer, the thickness of sapphire substrate and AlN transition layer on the surface thermal stress was analyzed. The results show that the radial stress of the epitaxial wafer is one order of magnitude larger than the axial stress at the growth temperature of 1 200 ℃. The distribution of thermal stress in the radial direction (d <Φ32 mm) is relatively uniform and the thermal stress range is ± 0.38%. The growth temperature is in the range of 600 ~ 1200 ℃, and the surface stress of epitaxial layer is approximately proportional to the growth temperature. The research results can provide references for the research of the growth process of such epitaxial wafers and the selection of screening criteria for low-stress epitaxial wafers.