Can single top metal be used for power/gnd ring?

[chris_li]

Hi Guys, in general, designer selects top and top-1 metal for power/gnd ring, one is for vertical direction and other is for horizontal direction.

However, can single top metal be used for power/gnd ring instead top 2 metals alternative? Any other concern or risk?

Thanks.

 

[rca]

No special risk, just like you mention the preferred routing direction will not be respected and will created some constraints for the STD cell router.

 

[ic_qiand]

hi, if u chose only one metal for PG rings, that means you will lay at least 4, long, fat, wires whose direction is different from the preferred routing direction, and APR tools can lay no wire to cross them.

 

[chris_li]

hi, if u chose only one metal for PG rings, that means you will lay at least 4, long, fat, wires whose direction is different from the preferred routing direction, and APR tools can lay no wire to cross them.

I see, thanks. But is it common and feasible?

 

[ic_qiand]

Yes! for example, sometimes we lay a analog macro cell, we only use a metal lyer for the PG rings.

I see, thanks. But is it common and feasible?