Merging Vias in ADS/Momentum

I am doing EM simulation using Momentum in ADS 2011. I also use Dynamic Link between Cadence and Momentum.

I am running into problems of being able to EM simulate a large via array in Momentum and would like to merge the vias into a "via bar" to enable faster EM simulation.

How can I do this in either Cadence layout or ADS/Momentum - again I am using Dynamic Link.

I have heard this was changed after ADS 2012, but I have ADS 2011.

Thanks.

The basic idea is: oversize - merge - undersize

Okay, thanks, not sure what that means.

In the Momentum Layout selection -> Via Simplification, we get this dialogue:

If I want to merge the vias on all layers in a "via bar" which selections do I choose from this dialogue ?

Should I do it all on layers ?

Thanks. See attached.

This was the generic recipe how to build a script for via merging: select via polygons, use oversize function so that they overlap, merge, undersize by the same amount.

But I see that your Momentum interface already has the via simplification feature.
- Local via arrays is ok.
- Merge vias keeping area and boundary means you wil get a merged via at the array bounding box, i.e. the effective cross section area will grow and total resistance is reduced accordingly. There are also settings to keep the cross section area. Try it, it's quite easy to understand what goes on.
- Max distance is the distance how far vias can be spaced to be recognized as a via array. In the technologies that I work with, via spacing between the layers is quite different, so this "one size fits all" might now work for you. If you use a large value, independent vias on lower layers in transistors etc. might be merged unintendedly. If your layout has no such critical cases, you can use large distance values from the largest via spacing.

Via bar:
When you do via simplification, make sure your merged vias don't behave as a regular metal with x-y current flow. Don't forget to change the physical via model from 3D to 2D , to avoid horizontal current flow in the merge via (via arrays have only vertical currents). In ADS emSetup, that setting is in Options > Physical model, not sure where the setting is in your Cadence interface.

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