Dust particle formation in low pressure Ar/CH4 and Ar/C2H2 discharges used for thin film deposition

This paper deals with the study of the temporal and spatial evolution of the dust formation in two types of capacitively coupled discharges in Ar/C2H2 and Ar/CH4 gas mixtures used for thin film deposition. To initiate the particle growth in the Ar/CH4 discharge it is necessary either to apply transiently high power to the discharge or to inject transiently a pulse Of C2H2. In the Ar/C2H2 discharge, however, the particles are formed spontaneously at constant low power. Due to the different initiation process the further temporal evolution of the dust formation is significantly different for both kind of gas mixtures. In the case of argon/acetylene the formation of dust particles shows a periodical behavior, which is not observed in the argon/methane mixture. The dust particles are detected by means of laser light scattering and by measuring the extinction of the laser after passing the discharge. The chemical nature of the particles was studied in situ by means of a multi pass FTIR-spectrometer. The thin film deposition was measured with an in situ ellipsometer. (C) 2003 Elsevier Science Ltd. All rights reserved.