60MHz电容耦合等离子体中电子能量分布函数特性研究

甚高频(频率大于30 MHz)耦合放电源由于能产生大面积高密度的等离子体而受到了人们的广泛关注. 采用电流、电压探针以及朗缪尔探针诊断技术对60MHz射频激发产生的容性耦合等离子体的放电特性及电子行为进行了研究. 实验结果表明，等离子体的等效电阻/电容随着射频输入功率的增加而减小/增加；等离子体中电子行为不仅依赖于射频输入功率，还与放电气压密切相关；放电气压的增加导致电子能量概率分布函数(EEPF)从双温Maxwellian分布向Druyvesteyn分布转变，而且转变气压远低于文献所报道的数值，这主要是由于在60MHz容性耦合等离子体中电子反弹共振加热效率大为降低. 关键词： 甚高频容性耦合等离子体 朗缪尔探针诊断 电子加热模式

Characteristics of electron energy distribution function of capacitively coupled plasma excited by 60MHz RF source

Capacitively coupled plasma (CCP) source excited by very-high-frequency (VHF) source has attracted much attention in semiconductor industry due to its ability to generate high density plasma with a large area. The electron behavior and discharge properties of capacitively coupled plasma excited by 60MHz RF source were investigated by using current and voltage probe and Langmuir probe techniques. The experimental results show that equivalent resistance or capacitance of capacitively coupled plasma decreases or increases, respectively, with the increment of input RF power. It is also shown that the electron behavior in the plasma is related not only with RF input power but also discharge pressure. Increase in pressure causes the transition of electron energy distribution function from Bi-Maxwellian type to Druyvesteyn type, with its transition pressure much lower than that reported by others, which is due to a great decrease in efficiency of electron bounced resonance heating in CCP driven by 60MHz.