Plasma flood system-physics of low energy electron generation, plasma coupling, electron transport and surface charge neutralization on wafer

Plasma Flood System (PFS) was developed for the Precision Implant 9500 to achieve the most advanced charging control on wafer surface for high throughput implant processes over a wide range of beam current. A novel configuration of plasma discharge chamber made it possible to generate primary electrons at between 0 eV and 5 eV while maintaining a high emission current of over 100 mA. Space charge limit in generating low energy electrons was overcome by combining the arc discharge chamber at the anode potential with a negatively biased confinement tube via a potential shielding. Magnetic field from the plasma source coupled with a filament induced field plays an important role in transporting low energy electrons out of the chamber. The system also has a feature to increase the emission by one order of magnitude by offsetting a reference potential of the plasma source. This paper discusses the physics of the PFS describing how the electrons are generated at below 5 eV and transported at a high flux into the guide tube held typically at -10 V