Detection of particles in rf silane plasmas using photoemission method

Abstract

Nucleation and subsequent initial growth processes of particles in rf silane plasmas are investigated using a newly developed photoemission method. In this method, electrons produced due to interactions of particles with photons (photodetachment, photoionization) are measured. Since threshold energies for the interactions are dependent on particle size, size ranges of the detected particles are determined by wavelengths of the irradiated light. Using this method, small particles such as SinHx (n≲10), SinHx (n≲200) and SinHx (n≳20) can be detected. The experiments show that even in a very early phase of their growth, particles nucleate and grow principally around the plasma/sheath boundary near the rf electrode, where short lifetime radicals are produced actively. This suggests that the short lifetime radicals are the key species contributing to the particle nucleation and its subsequent initial growth processes. Moreover, it is found that small particles exist even in the bulk plasma. Since some of them are considered to be neutral, they are likely to be transported to the substrate on the grounded electrode.