Plasma-sheath expansion around trenches in plasma immersion ion implantation

Plasma immersion ion implantation (PIII) has been developed as a fast and efficient surface modification technique of complex shaped three-dimensional objects. The temporal evolution of the potential surrounding the two-dimensional trenches during the PIII process is studied by a particle-in-cell simulation. The numerical procedure is based on the solution of the Poisson equation on a triangular grid and the determination of the movement of ions through the grid. A multi-level grid method is used for the solution of partial differential equation. The sheath evolution can be roughly divided into an ion-matrix phase (ions which are initially inside the trench are implanted) and a quasi-static expansion phase (ions enter the trench from the surrounding plasma starting at the receding sheath edge). The temporal potential evolution and the ion trajectories around trenches during the voltage pulse are demonstrated. This procedure leads to laterally resolved concentration distributions and implantation profiles, showing good agreement with experimental results