Optical emissions from electron-impact-excited tetra-ethoxysilane

The optical emission spectrum in the spectral region 200-800 nm produced by electron impact on tetra-ethoxysilane (TEOS) under controlled single-collision conditions is analyzed. Absolute emission cross sections (at an impact energy of 100 eV) of 0.7±0.2×10^-20 cm² for the Si (3p4s ¹P⁰→3p^{2 1}S) line at 390.6 nm, 2.4±0.5×10^-20 cm² for the CH(A ²Δ→X ²Π) band centered around 430 nm, and cross sections below 0.5×10^-20 cm² for the hydrogen Balmer-α, -β, and -γ lines at, respectively, 656.4, 486.1, and 434.0 nm are measured. Comparatively high onset energies of 56.2±2.0 eV (Si) and 30.7±2.0 eV (CH) were found which when combined with the small cross sections indicate that the single-step dissociative excitation of TEOS by electron impact cannot be expected to play a major role in the collision processes that dominate the plasma chemistry of TEOS-containing processing plasmas.