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C 00
Safety recommendations
for harsh processes
G 04128 - Edition 02 - July 12
SPECIFIC adixen RECOMMENDATIONS for processes using SiH
4
and H
2
For these applications, using SiH
4
or H
2
, adixen recommends:
1) To avoid O
2
in process vacuum line after process chamber maintenance : O
2
may likely react with
trapped gases and deposited dusts & polymers.
Preferred solution:
adixen Vacuum Products strongly advise to use separated ‘load lock & transfer’ (clean) pump in order
to evacuate process chamber from atmospheric pressure down to 60 hPa (or less), using a soft pumping
step to limit particle transportation.
Alternative solution:
End User may flush process chamber and piping installation with nitrogen in order to decrease oxygen
concentration below MOC/LOC level with safety margin (ie [O
2
] < 2 % for hydrogen or 0.84 % for
Silane).
2) To avoid air inrush in vacuum line: a sudden air inrush could shake the fore line strong enough to make
powders fall and release pyrophoric gases. It could also lead to cloud creation which can be ignited
easily with very low energy.
Avoid ports on the fore line between process chamber and process pump, or secure them (i.e. a valve
must be equipped with a blank-off flange and a clamp which cannot be opened without a tool)
Use a main isolation valve which cannot be opened if the differential pressure is too high, meaning
that only a soft pumping valve can be used to evacuate the chamber from atmosphere
To use an efficient flow restriction (i.e. soft pumping) for chamber evacuating from Atmosphere
down to 60 hPa : In order to avoid cloud formation within flammable range of common species
3) To stop Roots blowers interlocked when chamber pressure is higher than safety level of 6 hPa, to avoid:
Si particles removal from pipe inner surfaces (generating Si dust cloud)
Generating Si dusts cloud due to high turbulences created at rotating parts contact.
Possible Roots exhaust overpressure which could increase effects of a possible explosion by
increasing the initial pressure.
4) To interface pumps with the tool: N
2
warning has to be considered as a safety issue (see interface
recommendations) with immediate interlock action on process gases inlet.
5) To flush the pump with N
2
(pump running) during at least 20 mn before to exchange it
6) To install additional protections to avoid projections if any component of the entire system cannot
withstand the pressure of an eventual explosion.
7) To minimize or secure quantity of inlets ports in the exhaust line which can become undesired leak
sources or sudden, air inrush.
8) To respect a safety area around the pump of 4 m minimum. This will prevent any damage on operators
ears due to overpressure shock wave propagation, as well as little fragments ejection - if any.
adixen Vacuum Products – A3H Series Operating instructions
