低气压容性射频放电中电流密度对鞘内离子能量通量的影响

Effect of Current Density on Sheath Ion Energy Flux in Low-pressure Capacitive Radio Frequency Discharges

研究了低气压容性射频放电电流密度与离子到达被加工材料表面的能量通量之间的关系。在Lieberman的射频鞘模型基础上,计算离子从等离子体内部到材料表面所经历的时间平均的总鞘电势差,发展了Lieberman的模型。并利用离子浓度和总鞘电势差的表达式推出到达材料表面时离子的能量通量与射频驱动电流密度的关系式。驱动电流密度对鞘内离子能量通量起激励作用:随驱动电流密度增加,离子能量通量单调增加。时间平均的鞘电势差与驱动电流密度的关系实验与理论模型进行了比较,结果呈现较好的吻合,为理论分析的正确性提供了证据。

The relation between low-pressure capacitive RF （radio frequency） discharge current density and the ion energy flux when reaching the material surface is investigated. Based on Lieberman＇s RF sheath model, the time-average total sheath potential difference from plasma bulk to the material surface is calculated to extend Lieberman＇s model. Using the expressions for ion density and total sheath potential difference the relation between ion energy flux when reaching the material surface and the driving RF current density is derived. The driving current density plays an impelling effect on sheath ion energy flux. With the increasing driving current density, the ion energy flux increases. The analytical model is compared with the experimental data of time-average sheath potential difference versus RF driving current density, which shows agreement and provides evidence for the validity of the analytical model.