Need for maximum density limit

[Amy25]

Hi All,

What is the need for a maximum density limit in DRC/density checks? What is the need for via density checks? How the maximum/minimum density limit is decided?

Thanks!

 

[erikl]

What is the need for a maximum density limit in DRC/density checks? What is the need for via density checks?

Both min. & max. density limits are important for achieving constant and equal layer thickness/smoothness over the full wafer after the CMP processes (done after each insulation layer formation).

How the maximum/minimum density limit is decided?

By the foundry and its process management.

 

[Amy25]

Both min. & max. density limits are important for achieving constant and equal layer thickness/smoothness over the full wafer after the CMP processes (done after each insulation layer formation).


By the foundry and its process management.

Thanks for the reply!

But can you please explain me what is the harm in not meeting minimum/maximum density requirements set by fab? specific to each

 

[erikl]

But can you please explain me what is the harm in not meeting minimum/maximum density requirements set by fab? specific to each

Very simple: the fab wouldn't accept your design. Remember: it's a design rule, you have to adhere to. "A rule is a rule is a rule".

Why? Because the fab couldn't guarantee constant layer thickness(es) versus the die and the whole wafer, and so the yield could collapse considerably.

They simply wouldn't fabricate such a design - at least not on a multi-client wafer. As a well paying wafer customer, you could possibly negotiate a small over-density against a special offer considering the expected yield penalty.

 

[Abhi Sharma]

Hi Amy,

because of uneven density in chip, when CMP is done , in less dense area dishing structures forms, which makes un-uniform subsequent layer formation.

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Hi Amy,

because of uneven density in chip, when CMP is done , in less dense area dishing structures forms, which makes un-uniform subsequent layer formation.

 

[starinspace]

Hi Amy,

because of uneven density in chip, when CMP is done , in less dense area dishing structures forms, which makes un-uniform subsequent layer formation.

- - - Updated - - -

Hi Amy,

because of uneven density in chip, when CMP is done , in less dense area dishing structures forms, which makes un-uniform subsequent layer formation.

You said dish is formed where the density is low. Can you please tell me what happens when the density exceeds the maximum limit? 8-O