NEW APPROACHES TO CHARGING CONTROL

In space charge neutralised beams a plasma exists. In a 20 mA, 50 keV arsenic beam used for source drain implants the Debye length is around 0.5 mm. Understanding and exploitation of this plasma is necessary in the control of wafer charging levels within each die, as opposed to wafer-scale control, so as to prevent current passing through thin gate oxides. This approach allows electrons of very low energy to be used for charge control. Many existing flood gun systems produce electron energy distributions with high energy tails. Exploiting the properties of the beam plasma allows true low energy (< 20 eV) electron guns to be used.