Particle Distributions and Laser-Particle Interactions in an RF Discharge of Silane

We report laser diagnostic studies of capacitively coupled RF discharges containing 0.05-0.45-percent silane in argon. We probed positions between the plane-parallel electrodes by pulsed laser light scattering at several wavelengths. These spatial scans had a resolution of 0.25 mm and they showed unusual particle distributions which varied with silane mole fraction and gas-flow rates. Particle nucleation and growth kinetics were very well demonstrated over this range of discharge parameters. We also studied particle photophysics and demonstrated that ultraviolet pulsed lasers (251.4 and 266 nm) can form silicon atoms from laser-particle interactions. Atoms were formed in both ground and excited states with a concentration that depended linearly on laser energy. However, atoms were not formed by 354- or 532-nm excitation. Particle excitation by 354 nm at energies > 0.5 mJ created a long-time (>0.1 s) perturbation of the discharge chemistry which linearly increased the steady-state (10 Hz) light scattering with increasing 354-nm energy.