Effects of gas temperature gradient, pulse discharge modulation, and hydrogen dilution on particle growth in silane RF discharges

The effects of gas temperature gradient, pulse discharge modulation, and hy drogen dilution on the growth of particles below about 10 nm in size in sil ane parallel-plate RF discharges are studied using a high-sensitivity photo n-counting laser-lightscattering (PCLLS) method. Thermophoretic force due t o the gas temperature gradient between the electrodes drives neutral partic les above a few nm in size toward the cool RF electrode which is at room te mperature. Pulse discharge modulation is much more effective in reducing th e particle density when it is combined with the gas temperature gradient, a nd particles above a few nm in size cannot be detected by the PCLLS method even after 2 h. Hydrogen dilution of a high H-2/SiH4 concentration ratio ab ove about 5 is also useful in suppressing particle growth in the radical pr oduction region around the plasma/sheath boundary near the RF electrode.