Effects of Gas Temperature Gradient, Pulse Discharge Modulation, and Hydrogen Dilution on Particle Growth in Silane RF Discharges

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Abstract
The effects of gas temperature gradient, pulse discharge modulation, and hydrogen dilution on the growth of particles below about 10 nm in size in silane parallel-plate RF discharges are studied using a high-sensitivity photon-counting laser-light-scattering (PCLLS) method. Thermophoretic force due to the gas temperature gradient between the electrodes drives neutral particles above a few nm in size toward the cool RF electrode which is at room temperature. Pulse discharge modulation is much more effective in reducing the particle density when it is combined with the gas temperature gradient, and particles above a few nm in size cannot be detected by the PCLLS method even after 2 h. Hydrogen dilution of a high H2/SiH4 concentration ratio above about 5 is also useful in suppressing particle growth in the radical production region around the plasma/sheath boundary near the RF electrode.