Detection of Negative Ions in a Helium-Silane RF Plasma

Publisher Website
Google Scholar
Abstract
In order to detect negative ions in a helium-silane rf plasma, temporal evolutions of the densities of electrons and ions are observed by square-wave-amplitude modulation of an rf discharge voltage. Densities of electrons and ions are deduced using a microwave interferometer and ion saturation current of a Langmuir probe, respectively. The experiments show that negative ions are formed in the plasma even for a low concentration of 0.5% silane and their density is estimated to be about 109 cm-3 which is comparable to the electron density. The energy of electrons which form negative ions due to attachment is estimated to be below 8.9 eV, that is, below the resonance peak energy of dissociative electron attachment to SiH4.