Reasons for following low and high densities in layout

[chandra Rao]

Hi,
I want to know about reasons for following low and high densities in layout(like for metals)
So please explain me

Thanks inadvance

 

[safwatonline]

Regensity

reliability wise, u need a uniform metal distribution among the die so that during CMP all parts on the die is equally affected .
i guess from yield point of view u need a small gradient of metal change (i.e. the metal concentration should change with a small rate among the die.

 

[PaloAlto]

Regensity

If you have an area with too low metal density, the covering oxide bends down and the vias connecting metals get disconnected.

 

[protonixs]

Re: Regensity

planarization of layers is required to ensure a flat surface. if a certain layer doesn't have a flat surface, there is a tendency of the succeeding layers to have a curvature leading to breaks(microfracture). this is the reason why there is a minimum density of a certain layer.
hope it helps...
regards

 

[chandra Rao]

Re: Regensity

Hi all,
Thanks for the reply.

According to all messages I understand that at the low density areas oxide layer over the metals gets bend down and succedding layers are effected ,
Please explain me how exactly it gets bend or give me any pdf on this.

Regards,
Chandra