13.56 MHz 低频功率对60 MHz射频容性耦合等离子体的电特性的影响

使用补偿朗缪尔探针诊断技术，研究了60MHz/13.56MHz双频激发容性耦合等离子体的空间电子行为，得到了电子能量概率函数(EEPF)随径向位置和低频输入功率的演变行为. 实验结果表明，13.56MHz射频输入功率的变化主要影响低能电子的布居，其影响随气压升高而加大. 在等离子体放电中心以外，EEPF呈现出双峰分布的特性，同时发现从放电中心到极板边缘，次能峰有逐渐向高能区漂移的现象，次能峰的出现显示了中能电子的增强的加热效应. 通过EEPF方法，计算了等离子体的电子温度、电子密度. 讨论了等离子体中的电 关键词： 双频激发容性耦合等离子体 朗缪尔探针诊断 电子加热模式

Effect of 13.56MHz low-frequency power on electrical characteristic of 60MHz radio-frequency capacitively coupled plasma

Dual-frequency capacitively coupled plasma (DF-CCP) driven by two frequencies of 60MHz and 13.56MHz was studied using compensated Langmuir probe technique. The change of EEPF with radial position and low-frequency input power was obtained. The experimental result shows that the input power of 13.56MHz mainly affects the population of low-energy electrons and the effect becomes greater when the gas pressure increases. The EEPF exhibits a structure of bi-energy-peak beyond the centre of discharge. The second energy peak drifts to the region of higher electron energy from the centre to the edge of electrode. The emergence of second energy peak could be attributed to the enhanced heating of middle-energy electrons. The electron density and electron temperature were calculated using EEPF. The plasma electron heating mechanism was discussed.