氢气甚高频与高频容性耦合放电等离子体特征的比较

Comparison between capacitively coupled VHF and high frequency discharge in H_2

开发了氢气甚高频(60MHz)容性耦合放电的PIC/MC模型。在模型中考虑了带电粒子(e,H+,H2+,H3+)与H2的21种碰撞反应过程,模拟了氢气甚高频放电射频电场和电势分布以及电子和氢离子(H+,H2+,H3+)粒子密度和平均能量分布,并与频率为13.56MHz的放电结果进行了比较。结果表明,相对于频率13.56MHz的放电,氢气甚高频放电等离子体电势增高,导致两电极附近的电场增强;另外,两鞘层厚度变窄并且电子和H3+离子平均能量减小,其总密度却增加。H3+离子为氢气甚高频放电空间的主要离子,H2+离子密度比H3+离子小约2～3个数量级。

This paper presents PIC/MC model of capacitively coupled very-high-frequency discharge in hydrogen. We take into account 21 kinds of collisions of charged particles （e, H＋,H2＋, H3＋） with H2. have simulated the electric field distribution, potential distribution, density and mean energy distribution of electrons and hydrogen ions （ H＋, H2＋, H3＋）, and have compared with those of the frequency of 13.56MHz. The simulation results show that the plasma space potential is enhanced with the increase of driving frequency, which results in the increase of electric field near the two electrodes. Besides, rf sheath thickness becomes thin and the mean energy of electron and H3＋ is decreased, while their total density is increased with the increase of frequency. H3＋ is the dominant ion in the H2 very-high-frequency discharge, its density being two or three orders of magnitude higher than that of H2＋.