Need for maximum density limit

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!

annelizabath said:

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

Click to expand...

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).

annelizabath said:

How the maximum/minimum density limit is decided?

Click to expand...

By the foundry and its process management.

erikl said:

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.

Click to expand...

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

annelizabath said:

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

Click to expand...

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.

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.

Abhi Sharma said:

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.

Click to expand...

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