Following the success of the openEMS simulations, I'm now looking to improve the BEOL model, and I'm looking at the silicon substrate now... Taking a look into the semiconductor criteria subsection at https://skywater-pdk.readthedocs.io/en/main/rules/assumptions.html#process-stack-diagram There's no indication of the P wafer dopant concentration or resistivity, and that's a vital piece of information for simulating inductors and other structures that "see" the naked substrate. I'm taking the substrate information of IHP process (2 S/m for the wafer, 5 S/m for a thin epitaxial P layer), but I'd like to ask: 1) is there a value for the wafer resistivity/conductivity for sky130? 2) does the sky130 feature an epitaxial layer, and if yes, what is its resistivity/conductivity?

From some document I have, I got a value of 4.4kohms/square for the substrate (with no information regarding high/low process corners). There is no epitaxial layer.

Thank you! Now, any information regarding substrate thickness? I mean, before or after thinning.

Do you care if the inductor is placed on top of an isolated pwell inside a deep N-well? It’s kind of like an epi layer. If so there’s more info available here: https://skywater-pdk.readthedocs.io/en/main/rules/assumptions.html It shows pwell depth, pwell doping concentration. Inside the r+c directory of the pdk I can see the pwell sheet resistance varies from 2.8k-4.8k ohm/sq across corners (try to grep rspwres). So the resistivity is about 0.2 to 0.3 ohm-cm based on 0.75um depth. Good luck.

I'm more after precise information to further refine the model I'm using, that's all. And, yes, the substrate plays an important role in determining the losses of basically any device at millimeter waves (even microstrips, because the bottom metals are thinner than the skin depth, and thus doesn't completely shield the signal strip from the substrate). From what Tim Edwards told me, Rsh for the P substrate is 4.4 kOhm/square. For a 750um wafer, that gives 0.3 S/m. Low, but that's actually a good thing for RF :^)

Can you share your your technology file for EM simulation?

@GS I uploaded two test benches to a github repo. You can find it here https://github.com/LeoGalloGomes/openems_on_sky130 But you have to define all the layers manually, that goes for the silicon substrate, dielectrics, metals and air box.

Thank Leonardo. Files looks good. I also have lic for Sonnet golden version , just neet material stack and i can run coil simulations with second tool too.

I pointed the file because inside I put the complete stack with all important parameters (dielectric K, metal conductivity, thicknesses and heights). You can check also the DRM page for sky130 to verify the information. I never worked with sonnet, so I can't help you with the technology file syntax...