Also i noticed that the DRC rule for p-tap only kicks in the moment i try to add a substrate contact.
If i didn’t have one to begin with i no get DRC errors but once i add it i see a ton of DRC errors on p-tap for transistors that are relatively far away .
So is there some sort of global substrate bias im over ridding?
Nikhil M
12/23/2021, 2:18 PM
I know i can use a deep Nwell to isolate some of the nmos but my entire circuit has a fixed body bias.
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Tim Edwards
12/23/2021, 9:48 PM
I assume you meant to say that the rule is that n-diff to p-tap distance must be less than 15um, not 0.15um.
Tim Edwards
12/23/2021, 9:50 PM
By default, the layout will have a single substrate bias of ground, if you have all nFET devices, or whatever the nwell is connected to if you have all pFET devices. If you want a body bias on nFETs that is not ground, then you need to have all those nFETs in deep nwell. In your case, it sounds like you want to drop a deep nwell structure under your entire circuit.
Tim Edwards
12/23/2021, 9:57 PM
The DRC rule for tap distance is always present but only if you have the DRC style set to "drc(full)", since the tap spacing computation is compute-intensive, and is not something that you normally want running interactively.
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