Numerical simulation of plasma sheath of non-uniformly biased target in plasma ion implantation

Summary form only given. Plasma ion implantation - deposition in an immersion configuration possesses excellent prospects in industrial applications. The biggest advantage is to treat objects with an irregular shape without complicated target manipulation or beam scanning. Experimental results have demonstrated its effectiveness to treat various types of conducting or semiconducting materials. However, the implantation dynamics of non-conducting materials is quite different due to the sample charging. When insulating samples are being implanted, the ion bombarding energy may diminish substantially due to capacitance effects. Our investigation shows that when charging occurs, the potential on the insulator surface decreases very quickly beginning at the initial time stage. The potential decreases gradually and slowly during the pulse plateau. The non-uniformity of surface potential on the target surface consisting of both the insulating sample and target holder distorts the plasma sheath in the vicinity and the implantation dynamics is consequently altered. We have conducted numerical simulation to investigate the different potential distributions for an insulating sample on a conducting target holder. A two-dimensional particle-in-cell (PIC) program is used in the work. The simulation conditions are: bias potential V/sub applied/ = -40kV, plasma density n = 3/spl times/10/sup 9/ cm/sup -3/, and electron temperature T/sub e/ = 4eV. The surface potential on the sample is assumed to be 0, 115, 3/5 and 5/5 of the applied bias, respectively. Our simulation results indicate that the plasma sheath configuration changes considerably and a low potential in the central zone leads to a lower ion dose. However, ion concentration happens within the rounded zone between the insulator and target edge.