Investigation of negative charging with plasma flood gun (PFG) during high current implantation

Implantation of semiconductor devices at very high beam currents can often lead to device damage due to charging. Depending upon the implant conditions, type of charge control system used and the device being implanted, the damaging field can be positive, or of negative polarity. While conventional secondary electron flood guns (EFG) have helped in addressing the concern of positive charging to some degree, the risk of negative charging persists due to the inherent high energy electrons present with this approach. Commercial high current implanters are now being increasingly configured with plasma based flood guns to overcome the concern of negative charging. This paper presents the first account of studies to investigate the negative charging aspect with PFG using charge-sensitive devices. Breakdown Voltage (V_bd) measurements have been made for devices with various gate oxide thicknesses (60 Å~235 Å) on N and P-type substrates implanted on high current implanters with both EFG and PFG systems and the results compared