IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Dielectrics Tuesday Sessions
       Session DI-TuM

Invited Paper DI-TuM1
Vibrational and Band-Gap Engineering of Transition Metal Oxides for High-k Gate Applications

Tuesday, October 30, 2001, 8:20 am, Room 130

Session: High K Dielectrics II
Presenter: S. Zollner, Motorola SPS
Authors: S. Zollner, Motorola SPS
R. Liu, Motorola SPS
Correspondent: Click to Email
CMOS devices will change around 2005, when the SiO2 thickness reaches 15-20 A and the gate length 0.1 um. Beyond that, the physical thickness of the gate oxide can no longer shrink, since the leakage currents due to tunneling render the devices useless. Instead of reducing the physical thickness, scaling the gate length is accompanied by increasing the low-frequency dielectric constant k of the gate oxide. Apart from a number of requirements related to stability under CMOS processing, new gate oxide materials need to have properties that can be engineered by changing the electronic band structure and the vibrational properties: (1) A large band gap with reasonable band offsets compared to the valence and conduction bands of Si. (2) A large lattice polarizability, which can be associated with a soft phonon driving a transition between two crystalline phases. In a way, engineering of the band gaps and band offsets of high-k gate oxides is not too different from band-engineered semiconductors, such as SiGe:C or InGaP for heterostructure bipolar transistors. Optical spectroscopies (spectroscopic ellipsometry from 300 um to 9 eV, FTIR transmission and reflection, UV Raman scattering) and x-ray structural analysis are ideally suited for a rapid screening of a large class of materials for potential high-k applications, since they do not require processing for electrical measurements. Ab initio band structure calculations can assist in the interpretation of experimental results. This talk will describe recent work on SrTiO3 and various transition metal oxides (TiO2, ZrO2, and HfO2). Specifically, we will show how the band gap of SrTiO3 can be increased by 0.5 eV or more through changing the composition, which reduces the leakage currents of metal-gate CMOS devices. @FootnoteText@ Collaborators: R. Gregory, P. Fejes, A. Demkov, J. Curless, Z. Yu, J. Ramdani, R. Droopad, K. Reid, B.-Y. Nguyen, T.E. Tiwald, J.N. Hilfiker, J.A. Woollam.