The Factors Affecting the Particle Distributions Inside the Silane PCVD Reactor for Semiconductor Processing

The distributions of particles inside the silane plasma chemical vapor deposition (PCVD) reactor were theoretically investigated by analyzing the transport phenomena of particles for various plasma conditions. We included the effects of fluid convection, particle diffusion, and external forces (ion drag, electro static, and gravitational forces) onto the particles to analyze the movements of particles inside the plasma reactor. Initially, we assumed that the particles are uniformly distributed inside the plasma reactor and showed how these particles move and how they are distributed for various plasma conditions. The dominant force for the particle movement is the electrostatic force in the sheath region and the ion drag force in the bulk plasma region. Both the electrostatic and ion drag forces are towards the sheath boundaries and most of the particles are concentrated in the regions near the sheath boundaries by the balance of both forces, but the particle concentrations in the sheath region and in the bulk plasma region are almost 0. The particle concentrations at the down stream sheath boundary become higher than at the upstream sheath boundary by the effect of fluid convection. As the electric field strength increases, the particles are pushed more strongly towards the bulk plasma region and the peaks of particle concentrations are shifted more away from the electrodes. As the particle diameter increases from 0.1 mu m to 10 mu m, the relative importance of fluid convection on the particle movement becomes more significant than those of particle diffusion, ion drag force, and electrostatic force and the particle concentrations at the down stream sheath boundary increase, while those at the upstream sheath boundary decrease. It is found that the movements of negative ions as well as the positive ions are also important for determining the ion drag force onto the particles in silane PCVD.