AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThA

Invited Paper EM2-ThA1
Ab Initio Study of High-k Gate Stack

Thursday, November 16, 2006, 2:00 pm, Room 2003

Session: Electronic Properties of High-k Dielectrics, Ferroelectrics, and Their Interfaces
Presenter: K. Cho, UT Dallas
Authors: J. Ha, Stanford University
B. Magyari-Kope, Stanford University
P.C. McIntyre, Stanford University
K. Cho, UT Dallas
Correspondent: Click to Email
At nanometer scale, materials behave differently from their bulk properties. Material properties become a function of their size and shape at 1-100 nm scale due to strong quantum mechanical effects and surface effects.  In this talk, we will apply quantum simulations to study high-k gate stack materials.  We will focus the main discussion on the modeling study of high-k gate stack system with emphasis on two interface problems: silicon/high-k oxide and high-k oxide/metal gate electrode interfaces. For the silicon/high-k oxide interface, we examine the effects of interlayer SiO2 between silicon substrate and high-k oxide (HfO2 or ZrO2). The driving force for SiO2 formation at the silicon/high-k oxide interface is identified and the correlation between the interface atomic structure and the band offsets is elucidated.  Furthermore, the internal SiO2-HfO2 interface is investigated to understand the source of fixed charge problems of high-k oxides. Our modeling study has identified the source of fixed charges, and we have proposed a practical solution to passivate the fixed charge source at the interface. For the high-k oxide/metal gate interface, we have studied the work function of candidate metal gate electrodes and identified the key mechanisms which control the work function of different metals at the interface. Our study has shown that the interface work function is determine by 1-3 monolayers of metal at the interface and that the work function control requires a direct control of atomic structures at the interface rather than the overall structure of electrode materials.