Theoretical Study on Dose Distributions of the Ball Bearing Treated by Plasma Immersion Ion Implantation

A two-dimensional (2-D) particle-in-cell (PIC) model was used to study plasma immersion ion implantation (PIII) process of the ball bearing. In the simulation, distributions of the normalized potential and the accumulated incident dose were calculated. In addition, the relationship among the minimum distance between neighboring ball bearings without sheath overlap, the implantation voltage, the plasma density, and the pulsewidth was obtained. When the voltage is -10 kV, the plasma density is 2.95times10⁸ cm^-3 and the pulsewidth is 10 mus; the minimum distance without sheath overlap is 38.0 cm. To evaluate the model, the potential in the sheath was measured using a probe. Experimental results are in agreement with the calculated values. The simulation results reveal that a large number of ions are implanted into the top part of the ball bearing, which shows bad dose uniformity. When the ball bearing is revolved during PIII treatment, the dose uniformity can be improved to 91.25% at least