柱面天线射频感性耦合等离子体放电模式特性的实验研究

Experimental studies on the properties of the discharge modes in a cylindrical radio frequency inductively coupled plasma

利用Z-scan、电流、电压探头,通过测量等离子体吸收功率、天线电流、电压、等离子体直流悬浮电位等多种参数,研究了匹配网络、天线耦合强度、导电地面积、气压等多种因素对E,H放电模式特性及模式转化行为的影响.基于Γ型阻抗匹配网络中串联电容对射频电源输出功率的影响,提出了E—H放电模式转化的正负反馈区概念.研究发现:在相同的其他放电条件下,处于正反馈区时等离子体放电易于产生跳变型模式转化,而且模式跳变的临界天线电流、回滞宽度、跳变临界功率、跳变功率差等参数均随阻抗匹配网络参数产生明显变化;在负反馈区内,模式转化过程趋于连续.由于阻抗匹配网络的影响,E—H模式的跳变电流并不是总大于H—E模式的跳变电流.在不同导电地面积、阻抗匹配网络、气压下,模式转化过程中等离子体直流悬浮电位的变化呈现多样性.

In this paper, Z-scan, current and voltage probe were used to measure rf discharge power, coupling coil rf current, voltage and dc plasma floating voltage in RF inductive dischargr, and the effects of impedance matching network, coil coupling intensity and the source ground area on the properties of E, H mode and the mode transition are investigated. The positive and negative feedback regions are put forth on the basis of the influence of the series capacitance in a F-type impedance matching network on RF output power of the RF power source. It is experimentally founded that under identical experimental parameters, the discharge mode evolution is apt to be discontinuous and continuous in the positive and negative feedback regions, respectively. In addition, the threshold coil RF current （or plasma absorbed power） corresponding to the mode transition, the hysteresis loop width, the difference in plasma absorbed power during the discharge mode transition vary evidently with the series capacitance of the impedance matching network. The threshold coil RF current of E-H mode transition is not necessarily higher than that of H- E mode transition. In combination with the influences of impedance matching network and discharge pressure, the modes of transition are diversified for different ground areas.