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Self-heating simulation

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Dear colleagues!

I deal with SPICE models for SOI MOSFETs. Self-heating effect is one of the most important problems for the designer because it's difficult to obtain the values of cth0 and rth0 parameters.

My objective is to study or create the methodology for the extraction procedure for these parameters.

Unfortunately I actually don't know how this effect is modeled by simulator. BSIMSOI model has a separate pin "t" for the "intrinsic" temperature, but how is this information used by simulator?

I found the following formula:
P=ΔT/rth + cth*δ(ΔT)/δt,
where ΔT is the difference between "intrinsic" temperature and ambient, t is time, P is the power dissipation.

How this "P" is used for recalculation of Ids?
Thanks in advance.
 

I don't know if you have the BSIM SOI manual from Berkeley, but it may help answer your questions:

Keith.

---------- Post added at 19:57 ---------- Previous post was at 19:56 ----------

Or the BSIM 3 version: **broken link removed**
 

Extracting the geometry dependence of these thermal R, C
values for a single device is "interesting". Modeling how it is
modified by what its neighbors are to, ought to be quite a
mess.

Particularly for devices whose X/Y dimensions are less than
BOX and wafer thickness, the thermal spreading is not very
straightforward.
 

keith1200rs said:
I don't know if you have the BSIM SOI manual from Berkeley, but it may help answer your questions:

Keith.

---------- Post added at 19:57 ---------- Previous post was at 19:56 ----------

Or the BSIM 3 version: **broken link removed**
Click to expand...

Thanks, Keith. Yes, sure, we used this manual, but there is only a picture with thermal R and C (I will post it here a little bit later), but it's unclear for me how a simulator solve the equations for SHE. Let's consider the simple example:
1) Ids is calculated.
2) P=Ids*Vds.
3) A simulator "knows" rth and cth.
4) As far as I understand the simulation process, Ids is to be recalculated to obtain a negative output resistance (static IV). The first question is how to recalculate Ids? The second is the following: does "P" is also recalculated after the Ids changing? So, when will the recalculation process stop?

dick_freebird, we need to understand the very basics before we try to develop the models for really interesting things :)
 
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