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UBC Theses and Dissertations

An investigation of age-causing molecular phenomena at the gate-dielectric channel interface of MOSFET devices Sheikholeslam, S. Arash


Complementary metal-oxide-semiconductor (CMOS) scaling has led to numerous reliability challenges. A major source of such challenges is the molecular phenomena at the channel/dielectric interface in Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET). In this work, MOSFET dielectric/channel interface is investigated, and hydrogen diffusion as the cause behind one of the major MOSFET reliability issues (namely NBTI) is characterized. Within the realm of device simulation, classical molecular dynamics bridges the gap between accurate but complex quantum chemical methods and crude but straightforward statistical/Monte-Carlo methods. In particular, classical molecular dynamics alongside customized forcefield parameters were used to study hydrogen dissociation and diffusion at the silicon/ silicon dioxide interface. Such processes govern BTI-like MOSFET aging. For the first time, a full molecular-level characterization of hydrogen dissociation and diffusion at the gate-dielectric/channel interface was developed. We also showed how some mechanical alterations may improve the MOSFET devices resilience to longterm NBTI aging. Further, new forcefield parameters were developed and used to predict some of the characteristics of high-k dielectrics and their interface with silicon dioxide. This work sets the grounds for a systematic, simulation-driven approach towards engineering reliable nano-scale MOSFET devices.

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