Characterization of fine particle trapping in a plasma-enhanced chemical vapor deposition reactor

The distribution and transport of fine particles trapped in a radio-frequency (rf) plasma-enhanced chemical vapor deposition reactor was investigated using a laser light scattering technique. Structured clouds of particles were observed at localized regions between the holes below the showerhead. Typically, at a high rate of gas flow, particles emerging from the showerhead holes overshoot the equilibrium position of the particle trap, and the particle clouds in the trap were small and thin (winding mode). At a low rate of gas flow, the particles are directly attracted to the trap locations, and large particle clouds (lumping mode) were observed. The particle number concentration of trapped particles tends to increase with increasing rf power and decrease with increasing particle size. When the gas flow rate is increased, a sharp decrease occurs at a certain flow rate.