Ion beam generation from sheath field of grid electrode and its application to surface treatment

As plasma immersion ion implantation using a conducting grid is very useful to reduce the effect of capacitance and charging in surface modification, it is broadly applied in the fields of insulating material implantation. On the other hand, there have been only few attempts to analyze the sheath dynamics including the conducting grid. If the bias voltage applied to the conducting grid is in the range of hundreds of volts for sputtering, or the energy for local restructuring of the atomic arrangement is much lower than voltage for implantation, the surface charge and space charge substantially affect the incident ion energy and ion current to the surface. The formation of the space and surface charges during one bias pulse period are thus analyzed through a one-dimensional and a two-dimensional particle-in-cell simulation. Experiment with the optimally designed grid on the basis of the simulation results is conducted, and the results of both cases with grid and without grid are compared. The improvement of adhesion is yielded by increasing surface roughness and chemical change in the polyurethane treatment using the conducting grid. (c) 2006 American Institute of Physics.