PhD Defense of Fabio GONCALVES PEREIRA

One of the most important device for semiconductor industry nowadays is the Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) which is hugely applied in the development of a vast number of electronic applications. The downscaling of MOSFET geometry has been a very successful process to improve the performances of Complementary Metal-Oxide Semiconductor (CMOS) devices.
The scaling of transistors dimensions according to scaling rules enabled the performance improvements up to the 90 nm technology node, but the continuous shrinking of MOSFET dimensions faces both physical and economical limitations. In order to overcome these limitations and achieve the performance requirement, several “boosters” have been explored by the semiconductor industries, notably the use of alternative device structures such as “Fully Depleted Silicon On Insulator” (FDSOI), whose architecture has been chosen to be explored in this work.
For advanced CMOS technology, robust and predictive electronic transport modeling is a major concern. This PhD work intended to improve the device modeling for ultimate FDSOI devices, with a particular focus on carrier transport. In this scenario, Technological Computer-Aided Design (TCAD) based on Density-Gradient and Drift-Diffusion models arise as a fast and powerful tool to support the technological development within the industry, however we have shown that their accuracy for predicting advanced nodes is often doubtful. In order to overcome this issue, we presented a two-dimensional simulation tool (UTOXPP) based on physical models which makes use of state of the art C++ architecture and accounts for a complete and friendly GUI. By means of Finite-Difference method, we describe a complete modeling strategy for the most important parts of the solver, namely 1.5D Poisson-Schrödinger, Quantum Drift-Diffusion and the mobility models from Kubo-Greenwood formulation and Nonequilibrium Green’s function (NEGF). Simulation results showed the efficiency of UTOXPP for solving electrostatics and the quantum effects for both carrier distribution and transport for the given devices. The objective of this PhD work has been achieved as UTOXPP delivers reliable results for advanced nodes in a timely manner, being an excellent choice for the industrial daily use.

Members of the jury :

• Mr. Gérard GHIBAUDO, DR, CNRS Alpes: President
• Mr. Arnaud BOURNEL, PR, Université Paris-Sud: Rapporteur
• Mr. Marc BESCOND, CR, CNRS Marseille: Rapporteur
• Mr. Raphael CLERC, CR, Université Jean Monnet: Examiner
• Mr. Denis RIDEAU, ING, STMicroelectronics: Co-supervisor
• Mr. François TRIOZON, ING, CEA-Grenoble: Co-supervisor
• Mr. Marco PALA, CR, CNRS Alpes: Supervisor