A Nodal Model Dedicated to Self-Heating and Thermal Coupling Simulations

Characterization of the Static Thermal Coupling Between Emitter Fingers of Bipolar Transistors

“…The presented novel r th -ratio method can already be performed if a single-finger and a double-finger transistor are available although a five-finger transistor connected separately or symmetrically allows the more convenient determination. Issues resulting from using the latter test structure being symmetrically contacted as presented in [14] were discussed. Extracted thermal resistances and coupling factors for different emitter finger distances and finger lengths are presented.…”

“…The method can be used to calculate self-heating for other geometries, numbers and locations of emitter fingers and transistors, and allows the geometry scalable generation of self-heating networks within seconds (in contrast to, e.g., 3-D FEM methods [3]). The complete methodology is expected to be also applicable to other calculation methods (see [14], [15]), architectures (DTI [28]), transistor types (FET, HEMT), and material systems (InP-HBTs).…”

“…Each finger is laid out in CBEBC configuration although one common base and one common collector contact pad is used for all fingers. The emitters can be connected separately or, as indicated in the figure, symmetrically (comparable with [14]). While the latter option saves the space for two emitter pads on the wafer, it also may be useful if low thermal coupling is expected, since the according temperature increase at least can be doubled and allows a more sensitive determination of coupling factors.…”

“…An alternative approach using a resistive network is presented in [14], whereas in [15], only a single equivalent thermal resistance is determined, which shows a small-signal solution for an SOI technology. Most aforementioned approaches rely on externally accessible thermal nodes in the electrical device model for realizing a thermal subcircuit.…”

A Scalable Electrothermal Model for Transient Self-Heating Effects in Trench-Isolated SiGe HBTs

“…The dynamic relationship between instantaneous power dissipation and the temperature rise due to self-heating is incorporated inside a compact model using a passive network. A variety of analytical models have been developed to scrutinize self-heating effects by connecting different electrothermal networks such as single-pole, Foster, Nodal, Cauer, and recursive networks at the temperature node of the compact model [11]- [13]. In addition to this, circuit design optimization requires geometry scalable models to get the best tradeoff between circuit speed, noise, and power consumption.…”