A collisional model for plasma immersion ion implantation

Summary form only given, as follows. In plasma immersion ion implantation, a target is immersed in a plasma and a series of negative short pulses is applied to it to implant the ions. A new analytical model is being developed for the high-pressure regimes in which the motion of the ions is highly collisional. The model provides values for ion flux, average ion velocity at the target, and sheath edge motion as a function of time. The model suggests that the transient ion flux at the target scales with J_c=√2eu₀ n₀ (1+ω₀t)^-5/7 , where ω₀ and u₀ are the characteristic frequency and velocity of the ions in the sheath, n ₀ is the density, and t is the time. These values were compared with those obtained from simulation and show good agreement. A review was also carried out (for comparison) of earlier work done at low pressures, where the motion of ions in the sheath is collisionless, also showing good agreement between analysis and simulation. The simulation code is PDP1, which utilizes particle-in-cell techniques and Monte Carlo simulation of electron-neutral and ion-neutral collisions