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Do I need dummy resistor when I draw well resistor?

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020170

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Dummy resistors maybe be needed to get good matching property.

In general, when I draw poly resistor, I always draw dummy resistor next to poly resistor.

1. When I draw "well resistor", however, do I need dummy resistor?

2. If dummy resistors are needed or not, what is the reason to support them?

Thanks
 

I think it is good to put a dummy resistor if its an array of resistor like two diamentional or you can put a well ring because these resistor may produce a high stress region
 

It's not needed, I think
 

020170 said:
...
2. If dummy resistors are needed or not, what is the reason to support them?
Click to expand...
You need dummy resistors if you have more than 1 active (= used) resistor and want to rely on a good matching of their ratio. The dummies make sure to provide a matching physical environment at the outer edges of the active devices.

If dummies are needed - or not - doesn't depend on which device is considered, or where it/they is/are positoned; only the matching requirement determines its need.
So you wouldn't need dummies for a single resistor (or any other device), as it doesn't have to match another one.
 

There are two effects which impact the border resistors in a WELL resistor array.

1. Lateral diffusion interaction
So the doping concentration is little higher if there is a neigborhood WELL

2. Implant mask scattering
The implants get scattered at the edge of the mask. So there are some scattered dopants from neighborhood mask.

The problem is that to my knowledge there is no fab which offers foundry service and deliver data for this effect. They measure typical matching with dummy but do not compare that to a nondummy. On the other side for layout organization it is better to have the dummy as spacing element so nothing harmful could be placed near the WELL resistor.
 

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