Enhancement of integrated circuits performance : metal gate electrodes and strained silicon MOSFETs



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Enhancement of the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) device performance has been achieved by work function engineering of Metal gates (controlling and lowering threshold Voltage (VTH)) and incorporating Strained Silicon as a substrate (higher mobility of the carriers). However there has not been any report on successful demonstration of low work function MOS Metal Gate Electrode and reliability of MOS Strained SOI devices. The thesis investigates a novel approach of tuning the work function of thermally stable Tantalum Nitride (TaN) metal gate using a Gadolinium buffer layer on Hafnium based high-k gate dielectrics. An NMOS compatible low work function metal gate resulting in lower VTH, has been successfully demonstrated. The thesis also explores the Bias Temperature Instability (BTI reliability) of the Strained Silicon on Insulator (S-SOI) MOSFETs for the first time. Degraded Reliability has been observed on strained devices and a plausible mechanism has been proposed.