Optimization of treatment conditions for industrial gears in plasma immersion ion implantation (PIII) using particle-in-cell (PIC) simulation

Conventional line-of-sight ion implantation of industrial gears suffers from dose non-uniformity, and plasma immersion ion implantation (PIII) is an excellent alternative. The technique has attracted the interests of engineers and scientists and been applied to the treatment of three-dimensional samples such as ball bearings, oil pumps, and biomedical products. In this paper, we employ particle-in-cell (PIC) simulation to configure the optimal treatment conditions for industrial gears. Owing to the periodic structure of the sawteeth, we need only to examine one tooth using a 2-dimensional model. The particle impact angle and local incident dose along the (r-theta) plane change during each implantation pulse. Therefore, it is important to determine the potential, electric field, and ion density distribution around the gear in order to optimize the implant uniformity and dose. Our simulation results show that most ions are accelerated at a normal angle towards the bottom of the tooth when the plasma sheath thickness is larger than the outer radius of the gear. Our model allows the determination of a suitable range of implantation pulse for different gear dimensions in order to attain better implant dose and energy uniformity on the sidewalls of the tooth.