Actually most polishers do use a vacuum  on their outer sealing of cassettes.
Normal procedure is to tape seal the cassette, poly bag seal with vacuum and
then outer seal a second poly or 'foil' poly bag under vacuum. Sometimes an
inert gas is used as well - but vacuum is the preferred way.
Releasing the vacuum in a class 100 or class 10 flow hood  will not flood the
cassette with particles as the cassette is tape sealed.

The internet has several companies that sell the bag sealers- I have a simple
one without the integrated vacuum and use a small vacuum pump with a hyperdemic
needle if I need to seal. I do not have a clean room so I never seal polished
wafers.

Here is one google search I did:
 http://www.google.com/search?hl=en&rlz=1C1CHMB_enUS291US304&q=bag+sealing+equip
ment+vacuum&aq=f&oq=&aqi=

Good luck
Cheers
Ken Smith

-----Original Message-----
>From: Shay Kaplan 
>Sent: Dec 2, 2009 7:47 AM
>To: mazzolari@fe.infn.it, 'General MEMS discussion' 
>Subject: Re: [mems-talk] shipping wafers
>
>Andrea,
>
>Many supermarkets have bags sealing with vacuum for packing food before
>freezing.
>
>By the way, I don't think wafers are packed under vacuum - more probably
>inert gas. This is because in vacuum packing, when you break the vacuum, the
>air + particles rush in.
>
>Shay

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