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Other CAD Tools >> Physical Verification, Extraction and Analysis >> Running LVS after extraction in Assura?
https://designers-guide.org/forum/YaBB.pl?num=1154500047

Message started by ah_bhong on Aug 1^st, 2006, 11:27pm

Title: Running LVS after extraction in Assura?
Post by ah_bhong on Aug 1^st, 2006, 11:27pm

Hi,
Can we run a LVS again after we do our extraction using assura ?
The purpose is to double check the extracted netlist with the original schematic netlist.
Because when you happen to use a "ill-written" extraction rule deck, you will find yourselves
at a loss when you start to do the post-layout simulation and all the simulation results look funny.

cheers
bhong

Title: Re: Running LVS after extraction in Assura?
Post by bernd on Aug 2^nd, 2006, 1:34am

Two reasons why I think that it won't work, if talk about
an extracted view, extracted netlist after parasicit extraction.

- Schematic vs. Extracted Layout

1. Your extracted view, extracted netlist contains additional
paristic elements which originates form the layout, but which
are not included in the schematic.

2.a. If you use a extracted view the interconnects are usually drawn
on the layer purpose 'net', whereas the extraction rules consider
most of the time the layer purpose 'drawing', like used in the layout
view.

2.b. If you use a extracted view not sure if the it contains all layers at
all which are necessary for device extraction defined in the extraction
rules.

Bernd

Title: Re: Running LVS after extraction in Assura?
Post by ah_bhong on Aug 2^nd, 2006, 2:23am

Hi Bernd,
Thanks for the discussion.
I can understand that the extracted view has the parasitic components,
What if the LVS engine can exclude the parasitic components and just
pick up the main components to do LVS in the extracted view?

cheers
bhong

Title: Re: Running LVS after extraction in Assura?
Post by bernd on Aug 2^nd, 2006, 2:40am

Quote:

What if the LVS engine can exclude the parasitic components and just
pick up the main components to do LVS in the extracted view?

Indeed that can be done by selecting
Output 'LVS Extracted View' only in the Assura RXC GUI
or by using '?lvsExtracted “t”' in the RSF file.

But then there are still 2.a, 2.b to worry about, but you can try
it.

What do you exactly want to check the LVS command rules
or the parasitic extraction?
And why do you doubt there are not correct?
Who does provide you with the rules?

Bernd

Title: Re: Running LVS after extraction in Assura?
Post by ah_bhong on Aug 2^nd, 2006, 3:06am

thanks bernd
i will try what u have suggested.
Ya, i was running my post layout simulation recently,
and realised that the DC runs are all wrong.
I spent quite sometime to debug my cct before i realised
that the problem lies with the poorly written RCX file.
The extracted netlist have some short-cct and open-cct somewhere,
although the i have passed the LVS using calibre before i do the assura RCX.
Anyway, the rules are provided by one of the largest foundry around .. :)

cheers
bhong

Title: Re: Running LVS after extraction in Assura?
Post by bernd on Aug 2^nd, 2006, 4:59am

In general an RCX run is based on a clean LVS run,
because the tools are using their LVS database for
parasitic extraction.

Assura uses a so called 'procfile' where the process
topology is defined and the resulting files
'RCXspiceINIT', 'paxfile_coeff' and 'cap_coeff.dat'
as run scripts and capacitance models.
So the parasitic results have nothing to do with
the SKILL like exctract.rul file.

The shorts and open caps can be possibly removed by
changing the run specific setting in Assura e.g.
?excludeFloatingNets.

Did you run an Assura LVS?
Did the Assura LVS pass and is it clean?

It's not a good idea to use two different tools
one for LVS and the next for RXC!

Quote:

Anyway, the rules are provided by one of the largest foundry around

So the should be correct, I assume other customers are also using them.

I would suggest to check you Assura RCX run settings rather than try
debugging the command rules and related files.

Bernd