Regarding Density fixes

[MANOJKUMARPALO]

Hi,

I am currently working as a physical verification engineer.
I have sound knowledge in fixing all kind of DRC and fixing density too.

But,in density itself why max density and min density is there?
Density usually refers to min density,but why max density needed to be fixed?
What will be the negative impact of max density during fabrication?

Please answer me.

Thanks and Regards
Manoj kumar palo

 

[rca]

The drc are here for yield performance.
Then it is better to respect them.
Also for example TSMC rule set have some recommended DRC, which help to improve yield.

 

[MANOJKUMARPALO]

For yield performance ,they could have set only density fix in the rule set.
Why there is a requirement to set min and max density separately?

Thanks
Manoj

 

[rca]

Min and max are for the yield consideration.

 

[artmalik]

There is always a limit for density metal, poly etc. The reason for both are related to amount of dishing that can be taken by the wafer during the chemical mechanical process(cmp) for metals and dopant implant for diffusion.

if the minimum density is not met then the cmp tool might remove more because it will not have enough resistance from wafer because unfiorm metal density will provide uniform resistance and support to the tool. Where the density is high , it will offer more resistance and vice versa. This will cause non-uniform polishing of the wafer leading to different stress on the mosfets.

So you have to have max/min for the density for each of the mask steps.

Min and max are for the yield consideration.