A compact, efficient electrical dual-circuit topology for the representation of transient thermal coupling is presented. Based on controlled sources, the method allows an arbitrary level of complexity to be used for each self and coupled response. Two possible variations on the circuit form, and the resulting requirements for model extraction, are developed. The method is applied to the modeling of transient thermal self-heating and coupling data for a pair of thermal sources representative of integrated device structures in semi-infinite homogeneous as well as trench-isolated substrates.

The prediction of a simple lumped representation of heat sharing through emitter interconnect in high-power multiemitter bipolar devices is compared to numerical thermal simulation and found to exhibit nonphysical results. Using numerical simulation, interfinger metal heat flow is characterized qualitatively in three dimensions and the requirements for a more accurate model are determined. A new modeling approach based on these insights, using segmented emitters and a coarse representation of the metal structure, yields results within 2% of those obtained from numerical thermal simulation for a wide variety of device geometries and substrate materials, with a simulation time reduction of more than an order of magnitude. Using the new model, an extensive series of simulations is performed for devices fabricated in Si, GaAs, and InP substrates using Al and Au for metallization. Reduction in maximum temperature due to the presence of emitter interconnect in these structures is found to be in the range of 5%-15%.