Hf-based high-K gate dielectric and metal gate stack for advanced CMOS devices

Abstract

In this thesis, firstly, a high quality MOCVD HfAlO dielectric film using a single cocktail liquid source as a new high-K fabrication method is demonstrated. The HfAlO film with 90% HfO2, which has minimum sacrifice of K value, shows a great improvement in thermal stability and the significant reduction of leakage current compared to pure HfO2 film. Secondly, it is found that the presence of silicon and its location at the interface plays a major role in thermal instability of effective work function of metal/high-K gate stack. Thirdly, it is found using the combination of semi-empirical approach and MIGS theory that FUSI gate has effectively MSi2 configuration at the gate dielectric interface. Lastly, it is found that there is a critical composition ratio (Ccrit) of Ni to Si in Ni-FUSI gate which starts to show a strong Fermi-level pinning and the Ccrit is dependent on the underlying gate dielectric material.