I'm getting some quite large custom devices made on standard silicon wafers-- what kind of variation can I expect from wafer to wafer as far as *thickness* goes? How about flatness and parallelism?
The specs I have are very loose (tens of microns, IIRC), and I suspect it's not a very important parameter for most users.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Should be around 600=B5m +/- 10=B5m to 20=B5m. Depends on what you order,
300=B5m wafers are also possible.And why do you care about a few =B5m?
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Is the actual (typical) variation that bad from wafer to wafer? How much will the thickness typically vary across the wafer?
It does happen to matter in my application.
r,
It really depends on the wafer manufacturer and how much you are wiling to pay. I have seen 10=B5m spec from wafer to wafer. If you pay extra, I am sure they can screen and select the uniform one.
Okay, I hoped someone might know what the *typical* numbers are.
Come to think of it, maybe I have a couple of blank 200mm wafers kicking around somewhere that I can measure.
Whether they know it or not, it's important - wafers get back-ground to order depending on the package. Most packaging requirements are looser than yours, but there are lots of requirements for very thin grinds these days (like smartcards and such), which require correspondingly tight tolerances. Here's a datasheet from Corwil, who do this sort of thing:
They can hold the thickness variation across a wafer to +/-1.5u, and wafer to wafer variation within a lot to +/-3u.
-- Mike --
an
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rI'm amazed they can do backgrinding after dicing.
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