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Saving Internal Junction Temperature of VBIC Bipolar Transistor Model

I'm working with a SiGe BiCMOS technology where the PDK desribes the HBTs with a VBIC 1.15 model. To assess self-heating of transistors, I would like to save the internal junction temperature (or the temperature rise above ambient).

Do you know how to do this, in particular what's the name of the variable inside the model?

Looking at https://designers-guide.org/vbic/release1.2/vbic1.2.va.html, it seems dT or Tdev would be useful, but using a Spectre save statement for this (save Q10:Tdev Q10:dT) does not work (No such output parameter, terminal, or internal node name.). But then the above Verilog-A model is much older than 1.15.

Any ideas? Thanks very much.

Frank Wiedmann over 1 year ago

At https://support.cadence.com/apex/techpubDocViewerPage?path=spectremod/spectremod23.1/Chap9_re_Component_Statements.html#pgfId-1036746 the output parameter tempeff is mentioned.
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sgcad over 1 year ago in reply to Frank Wiedmann

Thank you for your reply. Unfortunately, I still didn't find a way to save the junction temperature. I'm waiting for a reply from the foundry, hopefully they can point me into the right direction.
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sgcad over 1 year ago

After some more researching, I've found that

save Q0:trise

is accepted by Spectre. But the resulting output is just zero, even though the transistor under test clearly shows self-heating effects, visible as a slow increase in collector current when a pulse is applied to the base of a common-emitter configuration.

I'll submit a support case, hopefully this will shed some more light.
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Frank Wiedmann over 1 year ago in reply to sgcad

I suggest you try
save Q0:tempeff
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sgcad over 1 year ago

Brief update on this topic: Using saveOptions options save=all shows the temperature rise from self-heating as Q0:dt. But save Q0:dt does not work to save this node with saveOptions options save=allpub. This seems to be a "missing feature" of Spectre; support is still looking into it.
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