Which metal layer is preferred for clock routing?

[prithivikumars]

Hi,

In 7 metal layer process which metal layer is preferred for clock routing? What is reason?

Prithivi.

 

[master_picengineer]

Clock Routing

Hi,
I think that the 7 layer is the better to reduce delay and power consumed in the clock tree.

 

[prithivikumars]

Re: Clock Routing

Hi,

If we route in 7th metal layer we will be having more capacitive effect. It will give more delay right.

Correct me if I am wrong.

Prithivi.

 

[master_picengineer]

Clock Routing

I 'm not expert in this field. Perhaps I am wrong. There is a compromise. You know that Delays are function of C and R. If we route the 7 th layer we'll have more capcitive effect and less resistif one.

 

[jedy206]

Re: Clock Routing

sometimes top layer are thicker... so just use standard layer and let the router do the stuff for you.
Fred

 

[vlsitechnology]

Clock Routing

first preference goes for power
metal 7 and metal 6 goes for power and remaining higher layers will go for clock routing bcz for higher layers the resistance is less so less ir drop

Bye take care

 

[iwpia50s]

Clock Routing

Middle routing layers such as 4, 5, and 6 tend to have the same characteristics so the clock can be more predictable on those layers. Also, fewer vias are required to connect to the metal 2 clock pins on the flops. As stated by jedy206, the top layers are sometimes thicker, and as stated by vlsitechnology, the top layers are usually reserved for power.

 

[kpec1988]

hi
To route the click signal it is better to route it through inner layer e.g.layer 2 or 4 because it will readiate small amount of electromagnetics wave so it will not create any EMC/EMI issue