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Which metal layer is suitable for power routing around chip?

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skyismylimit

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Routing Power

Which metal Layer is suitable for power routing around the chip and which metal for the POWER MESH???
 

Re: Routing Power

top metal due to its low resistance. but you need to use many layers of metal to deliver your power, there is trade-off between your IR drop budget, your signal routing area and EM limit.
 

Re: Routing Power

can anyone explain the calculations behind to find that which metal layers are suitable for power routing?

if there is any materials pls upload it
 

Re: Routing Power

But in some books they try to use metal 3 and metal 4 (5 metal layer process) for power ring and power mesh and not the top metal??? why is it so??
 

Re: Routing Power

There is too little information to say why. Can you give more information like what kind of package the circuit is use, is this an ASIC digital chip or analog chip, do they use laser pad..? In general you try to use higher level metal to deliver your power and provide shielding for important signals, but you also need to consider your manufacturing and testing technologies.
 

Re: Routing Power

Because you should think every gate can work under certain voltage, The same, we shouldn't think that IR is affect work of circuit and try to small IR. Power should routing on top met.
 

Routing Power

Wide metal on top
Narrow metal on bottom
 

Routing Power

If you access to the technology file, you can find the sheet resistance on each layer of the metal. Those numbers are different on each layer.

Picking the top layer of metal for the power truck, designers are considering the low resistance / low IR drop (the top layers are thicker than the lower layer in most of the processes)

Picking the middle layer, designers are considering the routing resources. For example, using power mesh from the top layer, you can imagine the routing will not be that easy.
 
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