[SOLVED] p diffusion guard ring around pmos

[preethi19]

Hi i need to make a guard ring around pmos. I need a p diffusion guard ring. So is there a specific way to create the guard ring. I mean i wasnt able to find a particular layer in the LSW window for guard ring so i searched online and i saw some places they were mentioning some layers that i can't even find in cadence. Can someone pls help me. by p diffusion guard ring do they simply mean by the normal nplus and pplus diffusion layers in the LSW??? Becoz i doubt its that because i dont think i can just place a pplus layer on top of a pmos.... Can anyone please help how to do this... Thank you!!!

 

[jebaspaul]

Is there anything like 'ntap' or 'ptap'.

 

[starinspace]

Preethi,


P diffusion guard ring means the ring with active layer, p+ diffusion layer, metal1 and contacts i.e basically its a P+ substrate pick up in the form of ring.
You can get diffusion rings by using create--> multipath part or create--> guard rings in the cadence virtuoso/icfb. Press F3 and change the type of ring that you want to create.

There is no particular kind of guard ring layer in LSW that can be used as far as my experience goes so far for 3 yrs.

Note: when you create multipath part ( multiple paths will come together when you draw once i.e diffusion,met1 with contacts,active layers) you can also create your own path with double contacts for the ring or wider guard ring or guard ring with some other layer with it etc.

 

[preethi19]

no there is nothing as ptap or ntap.... Oh i get it now thank you!!! So rather than multipart can i just form a ring around the pmos using simple rectangles that we use to make like wire connections. Like so i have to have the following layers in order from the LSW...
1.pplus
2.active layer
2.metal1
3.contact.

Also say i make a ring around my pmos and then place the first 3 like a full ring... But can i just place one contact for the overall ring and give it to vss??? becoz i saw using multipart will place contacts all around the ring?? Is that really necessary when we can just have one contact... Also They have asked me to connect it to groud. But i am using Vss in my layout and i am getting an error when i use both vss and gnd together.. So will it be right to connect it to vss. I think it wont matter right becoz all we want is to bring the potential of the guard ring low... where all the injected current to the substrate are taken to the ring and pulled by vss. This is what i read too. pls let me know if i am doing the right way.. Thank you!!!!

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But now i also am confused if we should use pplus for pmos or nplus. Because the substrate for pmos is n-well right so shouldn't we use nplus. Becoz pls check this link **broken link removed**... For NSUB (n substrate) the guard ring formed of nplus.... and this site
https://iccustomlayout.blogspot.ca/
had the following
"(ii) PMOS in the N-well should be surrounded with P-diffusion guard ring.
P-diffusion guard ring should be tied to ground. P-diffusions from the
PMOS inject stray holes into the N-well. These stray holes could be
collected efficiently by the P-diffusion guard ring that is biased to ground to attract the holes."

Please help!!!!