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To: Chas who wrote (43131)	2/19/1999 12:11:00 AM
From: steve kelly	Read Replies (1) \| Respond to of 53903

Chas, The only problem would be with high particulate contamination, this can generally be be cleaned off(at some levels no way). As for the wafers oxidizing, in the early stages of production that is a concern but approximately 60% of the way thru the process it is no longer a concern. So the delay in shipping product is not correct, wafers scrapped early in the process are not that big of a problem since most production lines can make up for loss pretty fast.

To: Chas who wrote (43131)	2/19/1999 1:08:00 AM
From: Fabeyes	Respond to of 53903

>>> I was told they oxidize when left exposed to the air or oxygen too long >>> This is common in wafer processing; you grow a native oxide when exposed to any air. Some locations within the process wafers are run through some kind of etch to remove this oxide. I would think the real problem would be contamination from the wafers sitting in a non-clean room environment. There are many other issues too -- like oxidation of metal (happen if wafers sit post deposition for more than 24-48 hours; is a real reliability issue). Wafers that have be run through a clean sulfuric acid have a tendency to "grow" concentrated sulfur based particles -- this happen at 2-3 hours, so staging to the next operation is mandatory. When some fabs have a shutdown they coat wafer with a thermal oxide to protect critical levels; it is an easy etch. The best thing though is not to expose gates to both oxide and non-clean air. Hope this helps a little. If there are terms that you do not understand let me know -- it is hard to talk to the "public" without getting into too much detail.