Spatiotemporal evolution of silicon particles in silane plasma was investigated with and/or without a crossed magnetic field using the laser light scattering method (Mie scattering) and scanning electron microscopy (SEM). Silicon particles were excluded from the discharge space in the opposite direction to the E x B drift, and then could be collected at about 1.5 x 10(10).cm(-2) on the upper substrate, in the opposite direction to the force of gravity. On the other hand, silicon particles were collected at about 6 x 10(10) cm(-2) on the bottom substrate, in the direction of gravity. Uniform a-Si:H thin film could be prepared by using the modulated electromagnetic field with the same frequency, f(EB) = 0.5 Hz. A possible mechanism is discussed to prepare large-area uniform a-Si:H thin film under the particle-for conditions using the modulated electromagnetic field and multielectrodes.