Possible contamination of wbdiff and wbnonmetal

Amol Ramesh Joshi amol at stanford.edu
Fri Nov 10 09:41:22 PST 2000



	Hi,

	Today I found a user doing nonstandard 'cleaning' on wbdiff and
wbnonmtal. He was etching oxide in 20:1 BOE and 6:1 BOE on wbnonmetal and
H2SO4 dip and HCl dip on wbdiff. He was holding just one wafer with teflon
tipped METAL tweezers, no cassette! As most users know, teflon on green
tipped tweezers tends to wear out after some use. So there is a very high
chance that metal may have entered the pots I mentioned above. I do not
need to mention safety issue, no matter how careful one is. I have
shutdown wbdiff and wbnonmetal.

	- Amol





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