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Effects of more VIA in electromigration

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meeyaw

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Hi all,

I am new to electromigration analysis and currently studying it.

About the number of vias to be used connecting two metal, does it mean the more VIA, the more electromigration resistant is the wire?

Consider the image below...

VIA_em_analysis.png

That VIA colored purple is VIA to M3, and the blue line is the Metal2.
I used that VIA with the intention of fix ground debounce on vss on Metal2
But I don't know if that kind of VIA will affect the electromigration on that part.

Thanks for the answers :)
 

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Increasing the number of VIAs reduces the current density inside each VIA. This helps mitigating the effect of Electromigration in your circuit.
 
AdvaRes said:
Increasing the number of VIAs reduces the current density inside each VIA. This helps mitigating the effect of Electromigration in your circuit.
Click to expand...

Thanks for the answer.

Follow-up question: But how can I know if the number of VIA is enough or too much on those affected areas by electromigration?
 

A tungsten plug via helps little, or not at all - it is a metal
flow barrier and prevents "makeup" metal from traversing
the via to help out. So metal piles up before, and depletes
after, the via in direction of current flow. In an all-aluminum
system without barrier layers, the constant migration has
some beneficial effect, extending the wearout time.

A tungsten plug will never wear out, but the abutting soft
metal will. And more vias help none, if they're tungsten.
You still will see the metal line recede from the last rank
with no replenishment. Only more width will help you. And
you can fill that width with more vias, because why not?
But expecting the count to help, is misplaced hope.
 

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