悬浮型微波共振探针在电负性容性耦合等离子体中电子密度的测量

本文首先利用悬浮型微波共振探针测量了Ar等离子体的电子密度,并与朗缪尔双探针的测量结果进行了比较,表明了微波共振探针在低密度等离子体测量的可行性.对40.68 MHz单射频容性耦合Ar/SF₆和SF₆/O₂等离子体的测量结果表明:电负性气体SF₆掺入Ar等离子体显著降低了等离子体电子密度,但随着增加SF₆的流量,电子密度表现为缓慢下降;而O₂掺入SF₆等离子体中,电子密度则随着O₂流量的增加表现为持续的下降.另外,40.68 MHz/13.56 MHz双频激发的SF₆/O₂容性耦合离子体的电子密度并不随低频功率的变化而变化.本文对上述的实验现象进行了初步的解释.

Application of floating microwave resonator probe to the measurement of electron density in electronegative capacitively coupled plasma

In electronegative or reactive plasmas, the problems such as negative ions floating near the sheath edge or deposition contamination cause more challenges for the diagnosis of conventional Langmiur probe. The electron density measured by microwave resonance probe is only a function of dielectric constant of plasma, there should be less or no influence of electronegative or reactive plasma. In this paper, a floating microwave resonator probe is proposed to measure electron density of capacitively coupled Ar plasma. A comparison with Langmuir double probe measurement shows that microwave resonance probe is applicable for measuring low electron density of plasma. The experimental results from the measurements of Ar/SF₆ and SF₆/O₂ capacitively discharge driven by 40.68 MHz show that addition of SF₆ into Ar plasma reduces the electron density significantly, with further increase of SF₆ flow rate, electron density shows a gradual decrease. While for the addition ofO₂ into SF₆ discharge, the electron density continuously decreases with the increase ofO₂ flow rate. Additionally, the electron density does not vary with lower frequency input power for SF₆/O₂ capacitively discharge driven by 40.68 MHz/13.56 MHz. The preliminary interpretations of the above experimental phenomena are presented.