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在微波等离子CVD设备中 ,微波电磁场的不均匀分布将导致等离子球和基片的温度不均匀 ,从而降低CVD金刚石的质量 ,因而基片加热是需要的。材料的吸收微波能的能力同微波频率、电场强度、材料的介电常数和介电损耗及材料体积相关 ,材料的介电常数、介电损耗、导热率又同温度相关。基于热力学理论 ,本文用强吸收微波能的SiC材料作为了基片加热材料 ,放在微波等离子腔的基片下 ,研究三维轴对称温度场模型 ,该模型的基片加热材料的介电常数、介电损耗和体积随温度变化 ,获得了温度分布的解析式 ,计算结果显示该模型能得到直径 76 .2mm的均匀温度分布 ,温度变化少于 10℃ ,因而可用于基片加热。
In a microwave plasma CVD apparatus, the uneven distribution of the microwave electromagnetic field will result in a non-uniform plasma ball and substrate temperature, thereby reducing the quality of the CVD diamond, so substrate heating is required. The ability of the material to absorb microwave energy is related to the microwave frequency, the electric field strength, the dielectric constant and the dielectric loss of the material, and the volume of the material. The dielectric constant, the dielectric loss and the thermal conductivity of the material are related to the temperature. Based on the theory of thermodynamics, SiC material with strong absorption of microwave energy is taken as the substrate heating material and placed under the substrate of the microwave plasma chamber. The three-dimensional axisymmetric temperature field model is studied. The dielectric constant of the substrate heating material, The dielectric loss and volume change with temperature were obtained analytically for the temperature distribution. The calculated results show that the model can obtain a uniform temperature distribution of 76. 2mm in diameter with temperature less than 10 ℃, which can be used for substrate heating.