Numerical simulation of plasma immersion ion implantation on the inner surface of a cylindrical dielectric target

Plasma immersion ion implantation of a cylindrical dielectric substrate target is simulated by a two-dimensional collisionless hybrid simulation (particle ions and Boltzmann electrons). In the model, the boundary between the dielectric substrates and plasma is handled by Gaussʹ law, and the potential of the internal area of the dielectric substrates is solved by Laplaceʹs equation. Using the model, the potential and the ion density distributions in the sheath are obtained. The spatiotemporal evolution of the surface potential and the incident dose along the inner surface of the cylindrical dielectric target are also calculated. The numerical results demonstrate that the surface potential on dielectric was greatly decreased owing to the charging effects and the capacitance of the dielectric. The incident dose is nonuniform. The dose peak is near the top of the bore. At the later stage of the pulse, another dose peak was created at about 0.8D (D is the ion-matrix overlap length) from the top of the bore. In order to get better implantation uniformity, it is helpful to end the pulse before the ions in the bore were consumed.