Optimization of two-dimensional grid electrode geometry for ballistic-mode plasma immersion ion implantation

Plasma immersion ion implantation (PIII) is a well-established technique for modification of surface properties of materials. Recently, the ballistic-mode PIII using grid electrodes was reported to modify the surface properties of insulating film¹. The ballistic-mode PIII can prevent arcing problem on the surface of film due to charging effect, and adequate to roll-to-roll process. Although the ballistic-mode PIII was demonstrated experimentally, the system has not been optimized. In this paper, the optimization of two-dimensional (2-D) grid electrodes is conducted to increase the dose of high-energy ballistic-mode ions. An analytic model was developed for the sheath expansion and ion distribution around 2-D grid electrodes, and used with PIC simulations to optimize the grid geometry effectively. The diameter of cylindrical electrode which consists of the grid electrodes and distance between cylindrical electrodes were chosen as optimization variables. The optimized geometry of the grid electrodes and the resulting ion dose of high-energy ballistic-mode ions is presented.