question on the power network in floorplan

[jackson_peng]

when draw the power supply network in floorplan,
why should we use the top two metal?
can anyone give the reason.

 

[jliang]

when draw the power supply network in floorplan,
why should we use the top two metal?
can anyone give the reason.

Less resistance? In cmos process, top metal layers have less sheet resistance. Correct me if I am wrong.

 

[anjali]

there should not be any volage swing for the cells/macros, if so they may go to metastable state or transistion delay problems etc.

so power network should have very less resistance. so we prefer the top 2 metals for power routing.

 

[nmtr]

when draw the power supply network in floorplan,
why should we use the top two metal?
can anyone give the reason.

really??? In our lab the top metal is used to route gobal and critical net and only the second and third level from top is used to power. any comments???