Contribution à la modélisation et à l’optimisation des effets d’auto- échauffement dans les TBHs Si/SiGe.

Abstract

The subject of this thesis is the 2D numerical modeling of an SiGe HBT (Heterojunction Bipolar Transistor) using the SILVACO-TCAD software. A simulation of the technological process was first adapted and carried out, and then we were interested in the electrical simulation. For this, we considered three electrical models: the DDM model (Drift Diffusion Model), the isothermal Energy Balance model (EB) and the Non-isothermal Energy Balance model (NEB). Due to the carrier’s overshoot and the non-isothermal effects present in the considered HBT, the NEB model was retained. In addition, the HBT SiGe produced in advanced technologies uses the Superficial and Deep Trenches Isolation (STI and DTI) as isolation between the different devices existing on the same chip. We have studied their impacts on the self-heating phenomenon and the static and dynamic performance of TBH SiGe. The results obtained showed that the self-heating phenomenon is accentuated in this case. In order to improve the electrical and thermal performance of the device, we were interested in analyzing other technological variants.Thus,we start by observing the beneficial effect of the ‘scaling’and the type of Si or SOI (Silicon On Insulate) substrate on the performances of the SiGe heterojunction bipolar transistor. Their effect is very significant on the improvement of electrical performances but an increase of the lattice temperature of the device is also observed. A technological solution to reduce this self-heating phenomenon is ""multi-emitter"" or multi-finger technology. An analysis of this solution was carried out and optimized and its benefit proven.