AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM+AS-ThM

Paper EM+AS-ThM5
Band Offsets Measurements of Metal/High-k/Semiconductor Structures

Thursday, November 16, 2006, 9:20 am, Room 2003

Session: High-k Dielectric Characterization
Presenter: S. Rangan, Rutgers University
Authors: S. Rangan, Rutgers University
E. Bersch, Rutgers University
R.A. Bartynski, Rutgers University
E. Garfunkel, Rutgers University
Correspondent: Click to Email
The study of high-k dielectrics and metal gate electrodes has been ongoing in order to thoroughly understand the properties of these materials and to contribute to their implementation in Metal/Oxide/Semiconductor Field Effect Transistors. The band offsets are an important property of Metal/Oxide/Semiconductor (MOS) stacks in that the leakage current depends directly on them. An understanding of the band offsets, particularly the role played by the interface dipole, may enable the development of tunable band offsets at the interfaces. We have used in situ photoemission and inverse photoemission as well as synchrotron photoemission to measure the band offsets between the layers of MOS stacks. UV, X-ray, and inverse photoemissions give us a direct measurement of the bandgap of the dielectric and offsets between dielectric and semiconductor bands. With sequential metallization (Al, Ru, Ti) shifts of the band edges are measured as a function of metal coverage. The band offsets we measure for the metal/oxide and oxide/semiconductor interfaces are, to first order, in good agreement with the modified Schottky Mott model which treats the interface with bare bulk (metal, oxide or semiconductor) properties. But as expected, photoemission reveals much more complicated interfaces, and in particular strong effects on the chemistry of the entire stacks upon metal deposition. We report here the energy gap and band offsets of several HfxSi1-xO2 oxides on a Si substrate, as well as the effect of Ru (high work function metal) and Al (low workfunction metal) deposition on theses dielectrics. Both Ru and Al induce an energy shift of the core levels (Hf4f, Si2p), the valence and conduction bands â?" the shift depends both on the oxide and on the metal choice. Ru stays metallic upon deposition on the oxide, whereas Al is shown to be oxidized even at room temperature. We will show that the source of oxygen can be the dielectric or the interface layer between the substrate and the oxide.