How to remove Gaurd rings in SBC18 process of Jazz - RF Cafe Forums

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ashishbondia
Post subject: How to remove Gaurd rings in SBC18 process of Jazz Posted: Thu Sep 28, 2006 6:37 am

Captain

Joined: Wed Aug 16, 2006 8:20 am
Posts: 23
Location: India
Hi!
I am trying to make a layout using Jazz SBC18 Process. I realized a BJT with multiplicity=10. Now when I am trying to generate a layout for the device, all 10 devices are sorrounded by gaurd rings. In order to connect these devices I have to remove the guard rings. But I don't find any way to do it. Can you help me with this

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Ashish Bondia,
Design Engineer- RF

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Stephen
Post subject: Posted: Thu Sep 28, 2006 1:20 pm

Captain

Joined: Wed Jun 21, 2006 8:33 pm
Posts: 21
Location: Queen Creek, Arizona
What do you mean by you can't remove them:

Do you mean that you can not physically change the layouts in a layout editor, because the guardrings are included with the BJT as part of a P-Cell or macro cell? If this is the case, you can flatten the instance of each BJT and then remove the guardring poly's. Note that this will break any library links (models, symbols, etc).

Or do you mean that design rules are not allowing you to remove the guardrings because of a DRC violation? In this case it is not a good idea to remove the guardings unless you have a buddy in the foundary process devlopment team who can vouch for what your are trying to accomplish.

Beyond this:
My next question is how is it that the guardrings are not allowing you to connect up the BJT's. Typically guardrings are only M1, so connectivity should be asily accomplished with M2? If these are RF BJT's, it may be that you do not want to remove the guardrings as they may have been included in the modeling and to remove them from the P-Cell will invalidate your model (or at least degrade the accuracy).

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CMOS RF and Analog ESD Specialist!
www.srftechnologies.com

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ashishbondia
Post subject: Posted: Fri Sep 29, 2006 12:32 am

Captain

Joined: Wed Aug 16, 2006 8:20 am
Posts: 23
Location: India
Thank you for your comments.
I wanted to remove the gaurd rings because I was tring to arrange the BJTs in a fashion so that I could use Both M1 and M2 for connections. the Base terminal of the BJT does not has M2. I also didn't want to use any M1 to M2 via.
While working with a different foundry I encountered a similar situation, However there the foundry manual provided enough informations on how to remove the rings and replace it with a larger one when I have connected all the BJTs and FETs

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Ashish Bondia,
Design Engineer- RF

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Stephen
Post subject: Posted: Fri Sep 29, 2006 1:29 am

Captain

Joined: Wed Jun 21, 2006 8:33 pm
Posts: 21
Location: Queen Creek, Arizona
Sounds like your set then, and yes it is a common practice to guardring the multiple legs/instances of a device, assuming they are all connected, with one large guardring as opposed to every leg individually.

Good luck.
-Stephen

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CMOS RF and Analog ESD Specialist!
www.srftechnologies.com

Posted 11/12/2012