Contamination is a very serious issue and can cause:
Damage to the MFC
Perforation of valve bellows and diaphragms
Destruction of filters
Loss of regulator control
Loss of sensors
Causes of contamination can be varied but may include:
Air in the gas system
Moisture in the gas system
Inadvertent connection of the wrong type of gas bottle
Corrupted gas in the bottle
Pinholes or micro cracks in valve diaphragms or bellows
Inadvertent opening of the gas system to atmosphere
Incorrect gas line heating
Incorrect gas line installation
Installation of components that were either improperly cleaned or not cleaned
Dusting of Silane or Silane based gas systems
Perforated flex lines
Installing new components in an improperly cleaned, contaminated system.
Normal use can also cause contamination as many gases leave residues.
Things to remember to prevent contamination:
When changing a gas bottle, the CGA fitting will be exposed to air and any
residual gas in that fitting will react and form a contaminate which will stay in
the system unless cleaned out or prevented. This contaminate will then enter
the gas stream and travel to the process chamber. The CGA fitting has a
bottle side as well.
If a component such as a valve or MFC is removed and it shows signs of
contamination, corrosion, etc. then the rest of the system is most likely also
contaminated the same way.
If new or refurbished components are installed in this system then they will
immediately become re-contaminated. Your work will be wasted.
Filters will trap contamination, when cleaning a contaminated
system…replace the filter .
If you have a system that is having flow problems after cleaning, did you
replace the filter ?
Always double check the gas bottle you are installing to ensure it is correct.
Never assume someone else has done something that was supposed to be
done, always check. Verify, Verify, Verify.
Always leak check a system prior to turning on the gas supply.
Always leak check a system after work is performed on the system.
Always purge and evacuate a gas system from the gas bottle to the chamber
prior to turning on the gas.
Use O-rings and seals that are compatible with the gas and the process.
Use MFC’s that are calibrated for the gas in use