Development of DC-PFG for a large size ion beam in ion doping system

A compact DC-plasma flood gun (DC-PFG) producing (50 mA) electron flux was developed for neutralization of a large size ion beam in doping process of flat panel displays (FPD). To produce the high current electron flux, this PFG contains a multi-cusp type arc chamber with a tungsten filament cathode, single hole to extract the electron and a drift tube with an axial magnetic field to send the electron into ion beam. The PFG doesn´t have any gas feeding but dopant gas flowing-in from an ion source for the ion beam formation. A real time measurement system of charge-up voltages on the FPD glass sheets in the midst of doping process was also developed. It adopts some thin film electrodes on the backside surface of glass sheet for voltage sensing. Using this system and additional electrostatic probes, it was concluded that the compact PFG could neutralize the large size ion beam and reduce the charge-up on the FPD glass sheets.