Inficon Transpector CPM, Руководство по эксплуатации

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4 – 8
Transpector CPM Operating Manual
4.4 Application
The pumping system reduces the pressure of process gas to a pressure at the ion
source which optimizes partial pressure measurements. The pressure reduction
orifices produce 2x10
-4
Torr pressure in the closed ion source (CIS). The flow rate
of gas that produces this pressure is:
Q(T-L/s)= P
CIS
S
CIS
= 2x10
-4
(Torr) x 0.7 (L/s)
= 1.4x10
-4
(T-L/s)
P
CIS
= the pressure at the CIS ion source within the CPM tee region
S
CIS
= the pumping speed of the closed ion source
Q
= throughput of the CIS ion source
This flow rate produced by process gas flowing through the process gas orifice is:
Q(T-L/s) = (P
Process
- P
CIS
) * C
Process Orifice
~1.4x10
-4
(T-L/s)
where the conductance C
Process Orifice
determines the orifice diameters needed to
produce this flow for each process pressure.
A selection of orifice diameters are available for reducing pressure for a
multi-decade range of (maximum) process pressures ranging 0.001–100 Torr.
For example, a 10 Torr orifice has a 20 micron diameter hole to produce
approximately 2x10
-4
Torr at the CIS when the process has 10 Torr of nitrogen.
Since process pressures can vary within the operating range of the process,
different pressure reductions may be needed. The CPM system has a variety of
inlet orifices that allow pressure range sampling which typically covers
measurement of the base pressure of the process chamber (for leak detection and
base vacuum analysis) with a high conductance port and two orifices for process
pressures. Various inlet systems are described with their typical use in
section 4.5 .