6
Recall that the mean ion beam current energy is typically 60 to 80% of the
anode voltage setting. Total output ion beam currents are similarly 20 to
30% of the anode current; this beam current is generally less at low gas
flows (high anode voltages) and greater at high gas flows (low anode
voltages). The output performance depends upon a particular vacuum
system’s actual pumping capacity, because of the interaction between the
source output and the process chamber’s background gases. Stable opera-
tion is generally possible for V
A
typically ranging between 50 to 300V and
for I
A
between 1 to 15A, depending on gas chemistry and the local pro-
cess chamber’s vacuum pressure.
Mark series Controller output is limited to 3kW. Refer to “Specifi-
cations” on page 63.
Additional information and reference performance curves for routine
operation appear in“Source Performance” on page 65.
Low vacuum pressures (less than 1.33 x10
-1
Pa/1.0 x10
-3
Torr) are gen-
erally necessary for stable source operation at high anode voltages
(greater than 200V); as a result, vacuum systems with marginal pumping
capacity may not support high voltage operation. A pumping capacity
greater than or equal to roughly 700
/s should be adequate for most
applications; this assumes there are no additional gas flows into the pro-
cess chamber other than those of the ion source and HCES.
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