Why Density check is required in lower technology nodes(14nm, 22nm etc)

[kishansmiles]

Can anyone explain me about the Density of metals/base layers(wherein we add the dummy/floating metals/base layers). I need some help from you guys, thanks in advance....


Thanks,
Kishan

 

[dick_freebird]

I've seen certain density checks as far back as the '80s,
10um feature size bipolar type stuff. You always have
some tradeoffs between diligence / layout style and
the lithography living up to expectations. The more
uniform the field loading, the more uniform the etch.
The denser the positive data, the more certain the
aligner tool is to find an alignable feature. Little things
that make it all work right.

So take your medicine. Nobody likes the taste. But it's
good for you.

 

[ms_90]

as we are going to lower nodes the fabrication process is getting complicated. so, at lower node we have to follow density rules. these rules dont allow the density below and above of the particular value.
example- for M1 the range is 30-70% at 28nm, means process doesnt allow density of M1 below 30% and above 90%

Now the question is why? what happens if density is below 30% or above 70%

when it is below 30(means min value) there will be chances that the poly in low density region will be etched out during etching due to large area will be exposed to etchant.

when it is above 60 dishing problem will be there...you can read about dishing on internet.