IN-SITU POLARIZATION-SENSITIVE LASER-LIGHT-SCATTERING METHOD FOR SIMULTANEOUS MEASUREMENTS OF 2-DIMENSIONAL SPATIAL SIZE AND DENSITY DISTRIBUTIONS OF PARTICLES IN PLASMAS

An in situ polarization-sensitive laser-light-scattering (PSLLS) metho d is developed to measure simultaneously two-dimensional spatial distr ibutions of size and density of particles in plasmas, in order to reve al growth processes and behavior of particles over a discharge space. The system developed can view the whole discharge area of 50X200 mm(2) illuminated by a sheet laser beam with a spatial resolution of 2X2X2 mm(3) and a time resolution of 33 ms, and measure particles larger tha n 50 nm in size and greater than 10(6) cm(-3) in density. Using the PS LLS method, it is found that particles formed in radio frequency silan e plasmas initially appear principally in an annular region around the plasma/sheath boundary near the powered electrode. Moreover, larger p articles tend to reside nearer to the powered electrode about 10 mm of f the discharge-column axis. The region occupied by particles spreads axially toward the grounded electrode (downstream region) and also rad ially toward both the discharge-column axis and the discharge wall, an d then particles flow out of the discharge space with a gas flow. (C) 1996 American Vacuum Society.