Why Ar decrease filament current for Ion Implantation?

[wjin]

As we know, filament current is one of the key monitor item for implanter.
Anyone know why Ar decreases filament current while Ge increases filament current for Ion Implantation?
Thanks in advance

 

[54chevy]

Ever heard of a fat filament or sputtering of the filament. If the filament gets thick it is harder to heat up and create a plasma therefore current goes up. If a filament is thin then current goes down, but if too thin and you raise the current for any reason you could open the filament and will need to replace it. Ar sputters the filament, makes it thinner. I belive Ge makes a filament fat which makes it need more current.... not too sure about Ge haven't worked with it.

Horacio