max-current annotations from RC extraction tools?

Does anybody know if there is a way to get LVS or RC extraction tools to inject max-current checks (electromigration limits) into the output SPICE deck? My preferred tool is Star-RCX.

Here's what I mean: every foundry publishes recommended electromigration limits for each layer of metal, usually in mA per um of line width. Once LVS has been performed the LVS+RCX tools both know which metal polygons comprise each net in the input netlist, so its possible for them to back-annotate the SPICE netlist with these limits.

It's probably better for the RCX tool to do this, since before RCX each net is just a single node even if it consists of multiple polygons of different widths on different layers. After RCX the netlist contains multiple nodes in a resistor network, and these can each be assigned the appropriate current limit. The RCX tools also usually do some sort of parallel/series reduction on this resistor network to keep the netlist size manageable, but the max-current limits can be propagated through this reduction pretty easily.

Ideally I'd like to wind up with HSIM's ".pcheck" directives in the output netlist so it will be watching my nodes for max-current violations during simulation. But for a general-purpose RCX tool you probably have to tell it "here's the template for the code I want you to inject for max-current annotations".

Anyways, it sounds like what I've described above would be really useful to a lot of designers, so I suspect it exists already. But I can't find anything about it in the Star-RCXT manual. Are there other RCX tools that offer this?

Thanks!

quantized said:

... for a general-purpose RCX tool you probably have to tell it "here's the template for the code I want you to inject for max-current annotations".

Click to expand...

Right: All what is done by the extraction tools is controlled by the corresponding extraction rules file. So if you study its syntax, you could possibly add yourself the rules for calculation and back-annotation of the electromigration limits. Formerly I've successfully done this with Assura & Diva extraction & drc rules for similar tasks (e.g. check for single contacts/vias). RCX extraction rules' syntax I don't know, however.

Some fab/foundry PDKs may already have included those EM rules, most of them didn't.

erikl said:

Right: All what is done by the extraction tools is controlled by the corresponding extraction rules file. So if you study its syntax, you could possibly add yourself the rules for calculation and back-annotation of the electromigration limits.

Click to expand...

I'm pretty sure this is not true for Star-RCXT. Let me know if you have evidence to the contrary.