PARTICLE AGGLOMERATION STUDY IN RF SILANE PLASMAS - IN-SITU STUDY BY POLARIZATION-SENSITIVE LASER-LIGHT SCATTERING

To determine self-consistently the time evolution of particle size and their number density in situ multi-angle polarization-sensitive laser light scattering was used. Cross-polarization intensities (incident a nd scattered light intensities with opposite polarization) measured at 135 degrees and ex situ transmission electronic microscopy analysis d emonstrate the existence of nonspherical agglomerates during the early phase of agglomeration. Later in the particle time development both t echniques reveal spherical particles again. The presence of strong cro ss-polarization intensities is accompanied by low-frequency instabilit ies detected on the scattered light intensities and plasma emission. I t is found that the particle radius and particle number density during the agglomeration phase can be well described by the Brownian free mo lecule coagulation model. Application of this neutral particle coagula tion model is justified by calculation of the particle charge whereby it is shown that particles of a few tens of nanometer can be considere d as neutral under our experimental conditions. The measured particle dispersion can be well described by a Brownian free molecule coagulati on model including a log-normal particle size distribution. (C) 1996 A merican Institute of Physics.