粉粒在等离子体中纯化的理论与工艺参数

Theory and technology parameters for particulate purity in plasma

针对反应室的情况,建立了硅粉的运动学模型和粉粒收集判据.应用该模型和判据,选择进气流速为5～2 0cm3 /min(标准状态下) ,抽气比例为0 .1.由于等离子区内只存在表面反应,钝化作用会使纯化效应消失.在鞘层内存在大量高能离子,除表面反应外,离子还能对粉粒表面进行刻蚀,因此钝化效应将消失.按此新的纯化概念,鞘层应尽量增厚.基于鞘尽模型考虑,在适中的压力、电流密度和直流自偏压下,选定鞘层厚度为1.5cm .刻蚀提纯的实验结果表明,硅的纯度可由99.0 0 % .提高到99.97% .

According to our chamber condition, the kinematic model and the collective criterion were established for Silicon particulates. The particulate diameters of 50～100?μm, gas flow rates from 5 to 20?cm3/min under standard stuation, and pump ratio of 0.1 were chosen with the model and criterion. The passivation effect made the purity phenomena elimilated, because there was surface reaction only in the plasma area. There were a lot of high energy ions in the sheath area, beside the surface reactions, the surface of particulates could be etched by the ions, and the passivation effect would be eliminated. From this new purity conception, the sheath should be as thick as possible. A sheath thickness of 1.5?cm was chosen to follow the moderate degree of pressure, current density, and DC self-bias voltage on the basis of the sheath model. The experimental results of etching purity show that the purity of silicon can be increased from ~99.00?% to 99.97?%.