In Situ Observation of Particle Behavior in rf Silane Plasmas

In situ observation of growth and behavior of particles formed in rf discharges of silane gas is carried out by using a Mie scattering method together with an rf modulation method, in which the applied voltage is modulated by a low-frequency square wave. The observation reveals that particles have a growth time quite longer than their extinction time and also are charged up negatively to be trapped in the discharging space. The drastic suppression of the particle growth realized in square-wave-amplitude-modulated rf discharges can be explained by taking into account the above features and further falloff of time-averaged densities of short lifetime species by the rf modulation.