why seal ring use a via bar instead of small square via?

[wcheow]

hi,

i am working on seal ring now and found that foundry does allow a long via bar between metal ring instead of conventional small square via. Anyone know the reason? thanks

 

[erikl]

The dimensions of "usual" vias are critical -- not so for the seal ring opening.

Standard vias must have unique dimensions in order to facilitate an optimized OPC shaping procedure (realized during "Data Prep" for mask generation), which is rather CPU-expensive. So with only one via size, only one figure must be optimized for OPC.

 

[michael eng]

The dimensions of "usual" vias are critical -- not so for the seal ring opening.

Standard vias must have unique dimensions in order to facilitate an optimized OPC shaping procedure (realized during "Data Prep" for mask generation), which is rather CPU-expensive. So with only one via size, only one figure must be optimized for OPC.

Critical rectangular vias are being used now. But other than putting in via bar by hand, are there tools for replacing square vias with via bars or implementing them in the P&R flow?

 

[erikl]

But other than putting in via bar by hand, are there tools for replacing square vias with via bars or implementing them in the P&R flow?

Within C@dence Virtuoso, you can put any x-y-arrays of structures, hence also via bars or fields -- admittedly only manually.
With the help of skill (or DRC) scripts, you could change rectangular vias into (bars of) square vias.