Capacitively Coupled RF Discharge Breakdown in Gas Mixtures

摘要

The RF (13.56 MHz) gas breakdown in Ne-N_2, Ne-Ar and He-N_2 mixture systems are investigated experimentally in a parallel plate capacitively coupled device with varying the pressure, the mixing ratio and the electrode separation, specifically focussing on the breakdown at the small values of the mixing ratio. The breakdown voltage curves obtained have the V-shaped or L-shaped characteristics. The breakdown voltage decreases with the addition of a small amount of N_2 or Ar in each mixture system, and the ratios of decrease in breakdown voltage to rare gas breakdown voltage in these mixture sysytems are about 22, 32 and 30 % at the maximum, respectively. The decrease of breakdown voltage is observed in a certain restricted pressure range, which is narrower in Ne-N_2 system than in Ne-Ar one. This feature in Ne-N_2 system is probably due to the decrease of electron energy attributed to the vibrational excitation of N_2 by electron impact. Compared with the DC breakdown and the microwave one, the decrease ratio in the RF breakdown is relatively small, suggesting that there exist some competitive ionization processes accompanied by excited particles including the Penning ionization.