ANALYTICAL MODELING OF PLASMA IMMERSION ION-IMPLANTATION TARGET CURRENT USING THE SPICE CIRCUIT SIMULATOR

Plasma immersion ion implantation applies a series of negative high-vo ltage pulses to a target immersed in a plasma. An analytical model of the currents and potentials induced before, during, and after the nega tive bias in a planar geometry is presented. The effect of multiple pu lses on the results is also studied. The model determines the time-var ying ion current, electron current, total current, total dose, and she ath thickness for a piecewise linear voltage pulse. The sheath collaps e is found to be important for high repetition rate pulses. Implementa tion of the model is done in SPICE, a circuit simulator. Comparison wi th experimental data has demonstrated the accuracy of the model.