number of gates in layout under diva

Hello,
i have layouted a transistor with 6 gates , i.e. number of gates=6
How to tell diva extractor that the layout is for one transistor with 6 gates
NOT 6 transistors in parallel???????
should i define a variable for my schematic or what???

thanx
MohamedAbouzied

Now, how do you have a transistor with 6 gates and they are not 6 parallel mos...?

Are your gates separated? you need one gate with six fingers.

The general way is to extract it as 6 parallel transistors and use "pruneDevice" rule in "divaLVS.rul" . If you insist on extract it as a single transistor with six fingers, you can use diffusion as recognition layer. However, it will fail if two transistors share a diffusion.

for malizevzek:
i have layouted one transistor with 6 fingers as u say not 6 transistors

for Hughes:
"The general way is to extract it as 6 parallel transistors and use "pruneDevice" rule in "divaLVS.rul" . If you insist on extract it as a single transistor with six fingers, you can use diffusion as recognition layer. However, it will fail if two transistors share a diffusion."

can u be more clear?
well, i don't understand what is "pruneDevice".
and that is only for LVS
but i want to do post layout simulations and i want it to be one transistor with 6 fingers not 6 transistors in parallel,
so if i put this diffusion layer on the big transistor with the 6 fingers, will it work?

and what u mean by two transistors share diffusion?

and thanx a lot
MohamedAbouzied

Is it possible for you to add a capture from your layout...?

Hughes, malizevzek and my questions are becuase Nr. of gates=6, Fingers=6 are ways to talk about parallel devices.
If not, (gates not connected each other) you do not have ONE transistor as you put in your initial question, you have 6.

In other words, if you want 6 transistors you can't use the #of gates parameter (or qty. of fingers, or multiplicity, etc) because all of them will be considered parallel devies.

Hi layoutmaster
I don't want 6 parallel transistors
i want a big one transistor

But when i do extraction, it is in the netlist as 6 parallel transistors which the case that i don't want.
Am i clear or not?

and thank you for your help
MohamedAbouzied

Added after 7 minutes:

and that is an image of my transistor:

I guess now understand it...

The important thing is that transistor's effective area is generating the BIG transistor you want nowhere you'll find it extracted as an UNIQUE huge transistor when it's drawed like this...

Nr. of Fingers, nr. of gates or Multiplicity = 6 always is related to 6 transistors is parallel, which are actually generating the big one you want but, again, extraction won't show you the effective one but the 6 in parallel...

Hope this helps.

so,
in post layout simulations, i simulate with 6 transistors in parallel?
That affects the simulations and degrades the quality of simulations.

so, no way to have one big transistor for the post layout simulations??

thanx again
MohamedAbouzied

If parameters ps, pd, as, ad are extracted properly, it will not degrade the precision of simulation. Anyway, it IS six transistors in parallel. Usually, a transistor with 6 fingers in schematic will be netlisted to a transistor with "m=6".

But if your mosfet model is a subckt with a parameter 'finger', then you may need to extract this way.

In diva extraction rule file, there is a statement like this:
You may modify it as this:
Then you use function "measureParameter" with keyword "fig_count" (or the like, please refer to Cadence Documents) to find out the finger count.

I don't have a diva reference at hand, the exact statement syntax above may be wrong. Please check it. To use "diff" as recognition layer, you need keyword "samenet" in the statement "extractDevice". Otherwise, you will get a device with 8 terminals ( for 6 fingers).

I agree with Hughes... I do not see a reason why it should degrade your sims...

By the other hand, under the layout point of view, what you posted in the picture is the correct way to layout these transistors.

I have checked "Diva Reference" and found some mistake in my previous post.

If you want to use diff as a recognition layer, you can't include keyword "physical" in the "extractDevice" statement. (No "samenet" keyword).

To count the fingers:

Still I don't think it necessary to extract a mosfet with a "finger" parameter.