Validation of Thermal Resistance Extracted From Measurements on Stripe Geometry SiGe HBTs

Abstract

In this paper, we present a straightforward methodology to validate the consistency of thermal resistance (RT H) measurements for a set of stripe geometry silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). The proposed approach is based on the behavior of frequency-dependent thermal impedance (ZT H) of HBTs. The key advantage of this method is its simplicity and ease of applicability because it requires no additional measurements than the conventional approaches to extract the electrothermal parameters. First we provide a physics based formulation to extract ZT H as a function of RT H. As a next step, we propose different normalization methods for ZT H in stripe emitter SiGe HBTs to validate the RT H used in our ZT H formulation. Finally, we substantiate our validation technique across stripe emitter SiGe HBTs having different emitter dimensions corresponding to STMicroelectronics B55 technology.

A Critical Review of Techniques for the Experimental Extraction of the Thermal Resistance of Bipolar Transistors from DC Measurements—Part I: Thermometer-Based Approaches

“…In gallium arsenide (GaAs)-based heterojunction bipolar transistors (HBTs) like InGaP/GaAs and AlGaAs/GaAs, considered the dominant technology for handset power amplifier design, the high thermal resistances are a consequence of (i) the low thermal conductivity of the GaAs substrate (one third of that of silicon), (ii) the lateral heat confinement due to mesa isolation, and (iii) the interlevel dielectric films [9,10,[12][13][14][15]. In silicon/silicongermanium (Si/SiGe) HBTs for mm-wave and near-THz applications, namely, wireless and optical communication, medical equipment, and automotive radars, the increase in thermal resistances is due to technology strategies devised to boost the frequency performance, like (i) adoption of oxide-based shallow/deep trenches and reduction of the spacing between intrinsic transistor and trenches, which hinder the lateral heat propagation from the power dissipation region, and (ii) horizontal scaling of the emitter, which drives higher current (and power) density; such factors have contributed to push the thermal resistances of single-finger HBTs into the thousands of K/W [16][17][18][19][20][21][22].…”