Two-dimensional simulations of a VHF H₂ plasma for different discharge gaps and gas pressures

A two-dimensional simulation on a VHF H₂ plasma (60 MHz) was performed using the plasma hybrid code, and plasma parameters were examined as a function of pressure for different discharge gaps. It was found that as the pressure increased, the H₃ ⁺ and H⁺ densities as well as the electron density had a maximum at a certain pressure, and the maximum shifted to high pressures as the discharge gap decreased. On the other hand, the H₂ ⁺ density decreased with the increase in pressure, independent of the discharge gap. The axial profiles of the H⁺, H₂ ⁺, and H₃ ⁺ densities showed that dominant ions were H₃ ⁺ in our pressure range.