Hi

First consideration is whether your system is open-load or load-locked.  It
is not recommended to run chlorine chemistry in open-load systems, as there
will always be chlorine adsorbed on the walls, which will be released when
the chamber is opened.  This will react with moisture from the atmosphere to
create HCl fumes which will affect operators and can cause corrosion in the
chamber.  The only way to avoid this is to use a nitrogen filled glove box
around the chamber.  This is not a problem if the system is load-locked,
except when the process chamber is being opened for cleaning.  Note, gas
(filter) masks should always be used when cleaning plasma process chambers,
due to the potentially hazardous nature of deposits in the chamber.

The other issue is how to deal with exhaust gases.  You will need to check
with the local environmental legislation to find the permitted emission
levels.  If you are only doing a small amount of chlorine work, there may
not be a problem, as some regulations are based on time-weighted emission
levels, so you will not need any exhaust treatment.  If you do need to
reduce the emissions, there are a couple of different techniques.  The
simplest is to use an aqueous scrubbing system.  This passes the exhaust
gases through a spray of either water or some other chemical such as sodium
hypochlorite.  This will dissolve all soluble gases (especially Cl2, HCl
etc.).  Alternatively, there are commercially available adsorption systems
that pass the exhaust gases over heated beds of lime and/or graphite to
remove the reactive species.  The choice will depend on volume of gas, cost
and whether multiple systems need treating.

Regards,  Martin

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