Can I just used M3 to fill all spaces? also from where I can get the information of how much empty space can be accepted by the technology and MOSIS?
because no such information available in the DRC of the PDK I have, also MOSIS advised that they don't do dummy filling. So, I want to do it manually and I want use only M3 (top metal in my process)
read the DRM carefully, there are density rules for most if not all layers. doing it by hand is laborous, impossible for modern technologies and chip sizes.
DRM? you mean Design Rule Manual?
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So, you think if I use all metal layers as timof suggested would that be OK?
Just read the rules, you will very quickly understand which layers need filling. Sometimes it is all metals and vias, sometimes is all but one, sometimes device layers need filling too. Go read the damn thing.
There is quite likely a rules set for density which will
happily tell you where you've fallen short. May be a
checkbox, may be a separate runset depending on kit
structure. This embodies the DRM's guidance and is
what the foundry will criticize your database to,
directly.
From this design rule manual:
4. Minimum Density Rule
Many fine-featured processes utilize CMP (Chemical-Mechanical Polishing) to achieve
planarity. Currently, for MOSIS, the ON Semi 0.50 micron and all the 0.35 micron (and
smaller) processes are in this category. Effective CMP requires that the variations in
feature density on layer be restricted.
See the following for more details.
But, I do not see any "details" in "the following".
The DRM seems incomplete - what layers should conform to the density rules, what are the minimum and maximum densities, etc.
Usually density filling - at least for process sizes > 0.1µm - is done by the foundry before mask prep.
Suggest to ask MOSIS about the right procedure.
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