Ion implantation system

A method of operating a plasma flood gun, comprising:

• supplying an inert gas into an arc plasma chamber;
• inducing, at a first time, a first filament current in a filament to heat the filament to a first temperature and emit first electrons from the filament for interaction with the inert gas to generate a first plasma in the arc plasma chamber at the first time;
• and
• measuring a first filament resistance of the filament, in-situ, during generation of the first plasma at the first time.

An ion implantation system, comprising:

• an ion beam source to supply an ion beam for ion implantation into a semiconductor wafer;
• a plasma flood gun to generate a plasma through interaction of electrons emitted from a filament with an inert gas, wherein the plasma interacts with the ion beam to neutralize at least some of a positive charge buildup on the semiconductor wafer from the ion implantation;
• and
• a controller, electrically coupled to the filament of the plasma flood gun, the controller configured to:
• calculate, in-situ, a filament resistance of the filament from a filament voltage across the filament and a filament current induced in the filament during generation of the plasma.