Comment lampoly SNF 2008-07-18 18:34:08: Process Qual

mtang at mtang at
Fri Jul 18 18:34:08 PDT 2008

Here are the results for resist and silicon etch rates in nm:
T = 124/488
C = 138/494
B = 111/489
L = 126/490
R = 122/479
Silicon etched is 4850 A with 1% uniformity and selectivity to resist of 3.8.
Expected is 4470 A with less than 5% uniformity and selectivity 3-4.5.
So, the etch rate results look good, though 8% higher than expected -- BUT -- the resist on the edges was observed to have been burnt or reticulated -- about 5 mm in from where the wafer is clamped.  This may be because of inadequate chamber conditioning done following the chamber clean.
Ran additional clean using recipe 99 - 10 wafers.  Ran another etch rate wafer.  The resist is still reticulated about 5-10 mm in from the edge.
I'll put this back up, but with a yellow warning as I'm not sure what is wrong at this point.  Again, the etch rate, uniformity, and selectivity are good, but the resist reticulation is not normal.  If you have a critical etch, then please confirm your own process before committing critical wafers.
Will continue to troubleshoot on Monday.

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