Experimental Characterization and Modeling of the Thermal Behavior of SiGe HBTs

Abstract

International audienceIn this paper, a simple and accurate characterization method of the thermal impedance of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) is proposed. This method relies on low-frequency S-parameter measurements in the 100 Hz-3 GHz frequency range. It is shown that feedback hybrid parameter h12 provides an image of the thermal impedance in the frequency domain, which is independent of the size of the transistor. Very short thermal time constants involved in SiGe HBTs are accurately determined by this method, as well as the temperature dependence of the thermal impedance in a truly simple way as electrical measurements can be performed in dc conditions either on a wafer or on an attached die. Finally, a nonlinear electrical equivalent circuit model is extracted, which can be readily implemented in computer-aided design software for nonlinear simulation of any SiGe HBT circuit

5. Reliability

“…Owing to these considerations, thermal effects can be viewed as an undesired, yet unavoidable, by-product of the technology evolution. Unfortunately, the enhanced heat generation (for a given dissipated power) and the reduction in heat removal have pushed the thermal resistances (R TH ) of SiGe HBTs into the thousands of K/W [ElR12,Has12,Sah12] and even beyond 10 4 K/W for small emitter windows, as evidenced by recent experimental campaigns conducted on transistors fabricated by STMicroelectronics (hereinafter referred to as STM) [dAl10] and IFX [dAl14]. Thermal effects can lead to a severe distortion of the DC device characteristics (e.g., [LaS09]), and also degrade the low-frequency and high-frequency (since the DC bias is altered) behavior; besides the performance penalty, they may also affect the long-term reliability, and even trigger destructive instability phenomena.…”

An approach for determining thermal resistance model parameters of SiGe HBT

“…Before that, we need to be able to accurately estimate the thermal characteristics of the device. There are many methods [4][5][6][7][8][9][10][11][12][13][14] for measuring the self-heating phenomenon.…”

Thermal Penetration Depth Analysis and Impact of the BEOL Metals on the Thermal Impedance of SiGe HBTs

“…Due to the strong relationship between electrical and temperature effects in these components [3], which is worsened by their positive feedback [4], a realistic and physics-based thermal compact modeling is mandatory; a reliable compact model must ensure accurate circuit simulations during the design phase [5], [6], which take into account the operating temperatures of the HBTs. In stateof-the-art SiGe HBTs thermal phenomena arise when a static power dissipation (Pdiss) is applied, but also when the devices are operated in dynamic conditions, since their thermal bandwidth is within few hundreds of MHz [7], [8]. Many works can be found in literature about DC self-heating effects [4], [9]- [11], but less attention is given to dynamic thermal modeling.…”