Question: How to find out the order of the thermal network needed for self heating assessment?
In order to model self heating in SOI MOSFETs, an RC equivalent has been made of the thermal network where thermal resistance and the thermal capacitance have been described. (Refer to Zhang et al 'On the Formulation of Self-Heating Models for Circuit Simulation')
Given this basic assumption, some other papers have used an n-th order thermal network for self heating assessments. In [1], a 4th order thermal nework has been used while in [2] a 3rd order is taken.
How do we know what should be the right order and why should a simple one stage RC network not be good enough?
[1] Scholten et al ‘Experimental Assessment of Self-Heating in SOI FinFETs’
[2] Karim et al ‘Extraction of Isothermal Condition and Thermal Network in UTBB SOI MOSFETs’
The thermal energy is transmitted through material differently depending on the volume thermal capacity and the cross-section where the thermal energy is flushed away. For some more details on this, please take a look at
http://www.ecs.csun.edu/~nhuttho/me584/Chapter%206%20Thermal%20Systems.pdf
Thanks Aparna Sathya Murthy and Ionel Marius Vladan for the materials. They do provide some insight into the background but somehow my initial query still persists. How to determine what would be say the best way to analyze a given network (here an SOI MOSFET). Thanks again for your advice.
Dear Arka,
Adding to the colleagues above, The heat is generated in the active layer of the device. This heat will be stored and conducted by the different layers of the device including the active layer. Every layer can be modeled by a capacitance representing the heat storage in it similar to electrical capacitance storing electric charge in addition to thermal resistance accounting for the heat flow in this layer similar to the flow the electric current. The question now how many layers we have in the SOI; the silicon layer which is the active layer, the buried SiO2 layer, the silicon substrate layer, encapsulation layer. The encapsulation may have multiple layers. So the order of the equivalent circuit which is the number of capacitors in it will be equal to the number of the different layers in the path of the heat from the source layer to the desalination layer.
Best wishes
Abdelhalim abdelnaby Zekry Thank you so much for the explanation, that does clear my basic query! I am personally looking further into this as well.
Dear Arka Halder,
The order of the equivalent circuit is given by the number of used layers (number of interfaces). A simple one stage RC network describe only one interface (two layers).
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