Particle-in-Cell/Monte Carlo Collision Simulations of Striations in Inductively Coupled Plasmas

Striations in inductively coupled plasmas (ICPs) appear as a series of cocoons beneath a coil through which a source current is driven. In this study, we have simulated striations in ICPs using the particle-in-cell/Monte Carlo collision method. The simulated effects of pressure on striation characteristics are in good agreement with experimental observations. It is found that the discharge structure and electron heating mechanism of striated ICPs are markedly different from those of normal ICPs. In particular, electron heating occurs once in one rf cycle in striated ICPs but twice in normal ICPs. Electron heating in striated ICPs may be ascribed to a strong self-excited electric field induced by the oscillating motion of the electron density at approximately the ion density, resulting in a high electron temperature. Furthermore, the relationship between the spatial period of the striation and the discharge space is put forward as a generation criterion for striations in rf discharges. Striations tend to occur when the region of plasma generation due to ionization is adjacent to walls where plasma is lost. (C) 2012 The Japan Society of Applied Physics