Numerical modeling of the influences of the duty cycle on plasma immersion ion implantation

The low pressure non-steady diffusion fluid model and the sheath collision fluid model are built to describe the dynamic behaviors of multiple pulses sheath in the process of plasma immersion ion implantation (PIII) planar target. The influences of duty cycle are obtained by solving the fluid models numerically. It is found that plasma diffusion can accelerate the sheath expanding. The process of plasma recovery is quick initially, and gradually tends to the steady state in the pulse-off time. The main consequence of a short pulse-off time corresponding large duty cycle is that an incomplete plasma recovery can be produced between the pulses. The maximal implanted ion current is decreased substantially, but the average implanted ion current is increased, and is maximal for the optimum duty cycle. Therefore, the appropriate duty cycle is favorable to modification processing for practical application.