Litho Process Check Fail

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Prashanthanilm

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Hi

When does Litho Process Check (Litho Friendly Check) Fails?
I am running on 40nm node layout (Standard Cells) for which I get all the cells passed for the LFD.

I want to make a test case for which LFD fails.
In pdk there is Hot Spot fix mentioned, I have tried few combination but all of these passes for LFD.

Any help is appreciated.

Regards,
Prashanth M
 

in the DRC deck there are rules which are "good to have" and "must have"..... the idea is to follow only "must have" rules ....and then when you create complex layout scenarios then you might get Litho process check fail. You can always go through the Litho process checks and create layout scenarios that fail but it might not happen in case of a conservative standard cell layout which is clean to all the Litho process checks by construction.
 

I've never seen this (I have yet to go below 180nm on
any real design job) but I would suggest you open up the
rules deck and see what they're after, if the docs don't
give you enough to go on.

I could conjecture about things like non-ortho geometries,
lonely vias and the like, but it's really your foundry's call
and I'm sure they're not mine.
 
Thanks Artmalik.

To understand better, Can you tell me a scenario where LFD fails (SC-> Does not fail?, What about Memory/IO).

- - - Updated - - -

Freebird,

LFD checks will be more severe in lower nodes. At 180nm, there should not be any LFD check error.
 

Hi,
In the standard cell layouts we usually do LFD(litho friendly design) for a single cell and FLFD(fast litho friendly design) when abutted with many cells.The DRC may be clean in a single cell but when the cell is abutted with many number of cells these LFD errors arise.Try to fix only the hot spots and recommended fixes.It is ok to wave the weak risk spots.Try to abutt ur cells with different libraries and then u can see whether ur cell is fully litho clean. .
 

Hi Anand,

Does it mean that LFD does not fail for a Standard Cell (Not Abutted).
 

Hi Prashanthanilm,
Yes the chances of LFD failing in standard cell(not abutted) is very very less.If your cell is clean for DRC,DFM and pattern check than it hardly fails in LFD wen not abutted.
 
Thanks Anand.

How does the LFD check work then?. Whether the LFD Check is "off" for Standard Cell and "On" during Abutment?

From the PDF, foundry have mentioned the Hot fixes, which are clearly drawn on Standard Cell Layout, as mentioned LFD is clean.

Can you pass a small test case (Image of Abutment) where the LFD Fails?.
Whether any Switch needs to be turned on/off?
Eg: Design_type CELL/CHIP or something else?
 

Hi Prashanthanilm,
See the standard cells libraries which we do will be used in various places in the top level so in the top level we dont know actually wher our cell is going to be used.If in the top level our cell fails the DRC we should again modify the cell.One more thing the Litho friendly design is usually taken care more in the lower nodes.In double patterning there are chances that we get hot spots wen we abut with different variety of cells.As mention before if the single cell is clean foe DRC,DFM and pattern check then getting hot spots in tat cell possibilities are very very less.if the cell has metal notches in the corner and wen abutted with other cell then getting risk hot spots is more.
 

Yes, Understand.
Eager to create test case for LFD Failure.

Thanks for the Info
 

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