You do need it 1" larger.  The mask sits on a little ledge, so a 4" wafer
could would not fit under a four inch mask - it would run into the edge.

David Nemeth
Senior Engineer
Sophia Wireless, Inc.
14225-C Sullyfield Circle
Chantilly, VA


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Tom Fan
Sent: Wednesday, July 16, 2003 1:27 AM
To: [email protected]
Subject: [mems-talk] Mask size



Hi all,

Whats the typical correlation between the sizes of photomasks and wafers in
MEMS fabrication? If I were to fabricate microdevices on 4" wafers, do I
need
4" or 5" photomasks? I learned from an Internet site that the masks should
be
1" larger than the wafers to be used. Is this customary or masks of the same
size as wafers can also be used? Anybody can clarify this issue for me?

Thanks,
Tom Fan


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