Soutenance de thèse de Marine COURET - 15 décembre 2020
Marine COURET soutiendra sa thèse, mardi 15 décembre 2020 à 14h00, dans l'Amphi J-P.DOM du Laboratoire IMS, sur le sujet suivant : "Failure mechanisms implementation into SiGe HBT compact model operating close to safe-operating-area edges"
Abstract : In an ever-growing terahertz market, BiCMOS technologies have reached cut-off frequencies beyond 0.5 THz. These dynamic performances are achieved thanks to the current technological improvements in SiGe hetero-junction bipolar transistors (HBTs). However, these increased performances lead to a shift of the transistors bias point closer to, or even beyond, the conventional safe-operating-area (SOA). As a consequence, several parasitic physical effects are encountered such as impact-ionization or self-heating which can potentially activate failure mechanisms, hence limiting the long-term reliability of the electronic device. In the framework of this thesis, we develop an approach for the description and the modeling of hot carrier degradation occurring in SiGe HBTs when operating near the SOA edges. The study aims to provide an in-depth characterization of transistors operating under static and dynamic operating conditions. Based on these measurements results, a compact model for the impact-ionization and the self-heating has been proposed, ultimately allowing to extend the validity domain of a commercially available compact model (HiCuM). Considering the operation as close as possible to the SOA, an aging campaign was conducted to figure out the physical origin behind such failure mechanism. As a result, it has been demonstrated that hot-carrier degradation leads to the creation of trap densities at the Si/SiO2 interface of the emitter-base spacer which induces an additional recombination current in the base. A compact model integrating aging laws (HiCuM-AL) was developed to predict the evolution of the transistor/circuit electrical parameters through an accelerated aging factor. For ease of use in computer-aided design (CAD) tools, the aging laws have been scaled according to the geometry and architecture of the emitter-base spacer. The model has demonstrated its robustness and its accuracy for different SiGe HBT technologies under various aging conditions. In addition, a study on the reliability of several integrated circuits has been performed leading to a precise location of the most sensitive regions to the hot-carrier degradation mechanism. Thus, the HiCuM-AL model paves the way to perform circuit simulations optimizing the mm-wave circuit design not only in terms of sheer performances but also in terms of long-term reliability.