Dissociation Processes of SiCl4 and Plasma Parameters measured by Transient Spectroscopy at the Beginning of a SiCl4?Helium dc Discharge

Abstract

We propose that the excitation or the dissociation mechanism and plasma parameters in a discharge can be estimated by. spectroscopic methods, such as the measurement of the transient behaviour of fluorescences at the beginning of a pulsed de discharge. Fluorescences emitted from excited atoms and dissociated fragments from 270 to 640 nm in wavelength are measured as a function of time at the beginning of a discharge of a He-SiCl4 gas mixture. The transient waveform of fluorescence is calculated by considering the experimental results of discharge current and voltage between electrodes measured as a function of time. From a comparison of the experimental and calculated waveforms of fluorescence it is concluded that the fragment emitting the light, SiCb, is excited in a single-step from SiCl4 by electronic collisions and the fluorescence-emitting fragments of SiCI3, SiCI, C12, CI, Si and CI+ in a discharge can never be excited by electronic collisions in a single step. Furthermore, an average electron energy in the plasma at a steady state is simply estimated from a measurement of the transient behaviour of emission lines from helium excited states. The result is in fair agreement with the value measured by using an electric probe.