Time-resolved optical emission spectroscopy of modulated plasmas for amorphous silicon deposition

Data from time-resolved optical emission spectroscopy (TROES) are presented from experiments on plasma modulation in a typical parallel-plate reactor used for the deposition of amorphous-silicon-based materials. The SiH4-H2, GeH4. SiF4, and SiF4-H2 systems have been investigated by varying the modulation parameters (period and duty cycle) and RF power. The mechanisms of excited species formation have been elucidated as well as their decay in the afterglow region. It has been found that SiH*, Si*, GeH* and Ge* originate from a dissociation-excitation process of the parent molecule, while SiFx* (x = 3,2,1) are formed by a direct excitation of the same species in the ground state. In addition, SiF2 radicals in SiF4-H2 plasmas exhibit the highest stability in the late afterglow region.