[Libre-silicon-devel] Status

David Lanzendörfer leviathan at libresilicon.com
Sat Jun 29 09:54:53 CEST 2019


Hi everyone
So the test run for increased polysilicon thickness in order to fix the 
leakage has been successful, as least from a visual point of view.
The nitride spacer walls are now visible under the microscope.

It just seems as if some idiot has put the wrong sputter source into the 
Titanium compartment for the NSC3000 which wouldn't have been a problem if the 
Varian sputterer wouldn't have spontaneously broken again on Thursday.

So now, as with mystery meals, I have no idea what exactly is on those wafers.
It's kind of reasonable that the film might be transparent, because of a 
different uniformity, but then again, it didn't dissolve in RCA-1 solution 
after more than 15 minutes, which makes the claim that it's "just a different 
etch rate" pretty much bollocks.

However.
Depositing more polysilicon (~300nm) seems like the way to go.
I don't wanna use more, because the higher the poly-thickness, the bigger the 
resistance between the Poly-TiSi2 and the actual SiO2 dielectric, which 
impairs the frequency behavior of the FETs.

It seems as if the folks have already processed our contract renewal, since I 
was able to log in on the NFF website and I'm able to book from Tuesday on 
upwards.

I'll prepare 10 new wafers on Tuesday, where I'll etch the STI and deposit the 
first LTO load (4 microns), then CMP 15 minutes, BOE until silicon becomes 
visible, again LTO (2 microns), CMP again 10 minutes, which should remove 
parts of the Silicon and leave silicon islands surrounded by LTO.

This way I can have a topology which isn't bigger than 200nm in dz (height 
difference) which will allow nicely connected polysilicon gates, with h=300nm

And this time I take CKs advice and check every sputter source for the 
markings on the back (they scratched the material identifiers on the back he 
said) before depositing

-lev
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: This is a digitally signed message part.
URL: <http://list.libresilicon.com/pipermail/libresilicon-developers/attachments/20190629/f595131d/attachment.sig>


More information about the Libresilicon-developers mailing list