Abstract
In this part, we propose a step-by-step strategy to model the static thermal coupling factors between the fingers in a silicon based multifinger bipolar transistor structure. First we provide a physics-based formulation to find out the coupling factors in a multifinger structure having no-trench isolation (cij,nt). As a second step, using the value of cij,nt, we propose a formulation to estimate the coupling factor in a multifinger structure having only shallow trench isolations (cij,st). Finally, the coupling factor model for a deep and shallow trench isolated multifinger device (cij,dt) is presented. The proposed modeling technique takes as inputs the dimensions of emitter fingers, shallow and deep trench isolations, their relative locations and the temperature dependent material thermal conductivity. Coupling coefficients obtained from the model are validated against 3D TCAD simulations of multifinger bipolar transistors with and without trench isolations. Geometry scalability of the model is also demonstrated.
Highlights
State-of-the-art silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) are popularly used in the front-end applications of communication circuits such as low noise amplifiers operating at sub-THz frequencies [1,2,3]
We have developed a scalable model for static thermal coupling factor in trench-isolated multifinger bipolar transistors including the temperature dependence of thermal conductivity of the semiconductor
The model is extended to predict the thermal coupling effect in multifinger device structures where each finger is surrounded by shallow trench isolation
Summary
State-of-the-art silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) are popularly used in the front-end applications of communication circuits such as low noise amplifiers operating at sub-THz frequencies [1,2,3]. The work provides an important insight that the coupling effect can be predicted from the modeling framework of self-heating, the application of the approach is limited only to structures without any trench isolation (see Figure 1). The model inaccuracy increases for a smaller heat source area as shown, with maximum error of around 22%, where we compared the cij model of [19] with the corresponding 3D TCAD simulation data for multifinger HBTs having different emitter geometries but no-trench isolation between the fingers. To the best of the authors’ knowledge, a physics-based analytic model for thermal coupling coefficients considering the temperature dependent thermal conductivity for trench isolated multifinger transistors is still missing in the literature.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
