Wafer floating potential for a high current serial ion implantation system

In situ wafer floating potential measurements were made during high current high dose ion implants. Implants were performed on a ribbon beam implanter, the Varian VIISta 80, that uses a plasma flood gun (PFG) for charge control. Real time potential variations were monitored simultaneously from different areas of the implanted wafer. The effect of plasma flood gun current was measured for different currents and beam energies. Results show that, even with the low beam density in VIISta 80, the Varian´s unique plasma flood gun, is still necessary to maintain device potentials below 5 volts