Particle growth and transport in silane plasma chemical vapour deposition

Abstract

The model equations for particle formation, growth and transport were proposed for silane plasma chemical vapour deposition and were solved numerically. We included the plasma chemistry of silane, particle nucleation by cluster formation, aerosol dynamics and transport of chemical species and particles. The evolutions of gaseous species and particles along the reactor were presented for several conditions of process variables such as reactor pressure, total gas flow rate and electric field strength. To reduce the CPU time in numerical simulation, we used lower values of electric field strength in the sheath region then the actual values and analysed the effects of electric field strength qualitatively. It was found that the concentration profiles of positive ions show peaks at the centre of the plasma reactor, whereas most of the negative ions are located in the bulk plasma region owing to the electrostatic repulsion from the sheath region. Most of the particles in the plasma reactor are located around the sheath boundaries, owing to the balance of the electrostatic force and the ion drag force. As the reactor pressure increases, the contaminant concentration and diameter increase in the plasma reactor. The lower the total gas flow rate the higher the particle concentration and the larger the particle diameter. The particle concentration and diameter in the plasma reactor increase abruptly as the electric field strength in the sheath region increases.