Contact & Via layout

[pawan_nayal]

Hi All,

I am new to deal with IC layout stuff. I am just wondering why contact and Via layout look like square whereas they are circular in actual. how we measure CD in layout?

what we see in GDSII layout printed in same way on mask ?

Thanks a lot

 

[renwl]

Hi All,

I am new to deal with IC layout stuff. I am just wondering why contact and Via layout look like square whereas they are circular in actual. how we measure CD in layout?

what we see in GDSII layout printed in same way on mask ?

Thanks a lot

completely square can not be implemented.

 

[leeenghan]

Hi,

Do you see that we can have DRC error when it is a square compare to if we draw a circule (e.g. a square cover more area than the circle).

The GDS might not be exactly the same as mask, but not in the way we discuss here. OPC might be performed. Also, there is also some sizing for different layer (e.g. it is difficult to draw 0.101 poly, but easy to draw 0.1 poly). Lastly, the mask might be 4x larger, but this does not affect the final chip.

Regards,
Eng Han

 

[srivatsan]

You can never get prefect square as the "input data", ie photolithography step does not contain all frequency spectrum to do "square".

GDSII could very well be altered to get what you "see" in GDSII, ie, after alteration you see the "actual" GDSII data!

Srivats