
36
Table 4.7: Electron back-streaming occurs at an accelerator voltage of 50 V. Optimized is 100V.
Source
Gas
Pressure Cathode Discharge
Beam
Accelerator
Neutralizer
X
10
-4
Heater
I
V
I
V
I
V
Heater Emission
(Torr)
(A)
(A) (V) (mA) (V) (mA) (V)
(A)
(mA)
8 cm
5 sccm Ar
2.6
3.96
0.33
55
100
1250
5
150
3.6
125
5 sccm Ar
2.6
3.96
0.33
55
100
1250
4
100
3.6
125
5 sccm Ar
2.6
3.96
0.33
55
100
1250
4
75
3.6
125
5 sccm Ar
2.6
3.96
0.35
55
110
1250
4
50
3.6
125
The accelerator to beam current (A/B) ratio in the power supply may require adjustment. The ratio
is entered into the power supply and will induce an alarm if the A/B ratio is exceeded. A typical
A/B ratio is 10% and at this condition, the power supply will alarm if the accelerator current is
greater than 10% of the beam current.
Step 8)
Neutralizer operation
When the BEAM button is pressed, the neutralizer emission current should increase. If the power
supply is in MANUAL mode, the emission current is determined by the given neutralizer heater
current. If the power supply is in LOCAL mode, the emission current will adjust to the E/B ratio
where the E/B ratio is emission current to beam current ratio. For typical applications, E/B is set
to 125% or greater. At this condition, the emission of electrons from the neutralizer is more than
the beam current. This will assist with the downstream conditions and minimize surface charging
and arcing.
Step 9)
Turning the source off and cool down.
The beam and source are shut off by pressing the source button. The power supply can be then
turned off. It is recommended to leave the process gas running while the source cools for
10 minutes. It is recommended cooling the source about 20 minutes before the vacuum chamber is
vented.