AVS 56th International Symposium & Exhibition
    Applied Surface Science Tuesday Sessions
       Session AS-TuP

Paper AS-TuP8
Relationship between In-Depth Profiles and Local Structures in HfSiO Film Studied by Photoemission Spectroscopy and Extended X-Ray Absorption Fine Structure

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Applied Surface Science Poster Session
Presenter: S. Toyoda, The University of Tokyo, Japan
Authors: S. Toyoda, The University of Tokyo, Japan
H. Ohfuchi, JASRI
H. Kamada, The University of Tokyo, Japan
M. Oshima, The University of Tokyo, Japan
G. Liu, STARC
Z. Liu, STARC
T. Sukegawa, STARC
K. Ikeda, STARC
Correspondent: Click to Email
High dielectric (high-k) transition metal oxide materials such as ZrO2, HfO2, and their silicates are widely investigated to reduce the leakage current from channel to gate, because SiON gate dielectrics have reached a physical thickness scaling limit of complementary metal- oxide-semiconductor (CMOS) devices. Among them, HfSiO and nitrided HfSiO are promising candidates due to appropriate band gap, soft reactivity to the Si substrate, and suppression of crystallization. In this study, we have demonstrated annealing effects on in-depth profiles and local structures in the HfSiO films by angle-resolved photoemission spectroscopy and extended x-ray absorption spectroscopy. HfSiO films with thicknesses of 2.0 nm were deposited on 0.7 nm SiON interfacial layers using an atomic layer deposition (ALD) technique. Annealing was performed at 850 °C and 1050 °C for 1 min in a nitrogen gas of 1 atm by the direct current flowing method through the Si substrate. Photoemission measurements were performed at BL-2C of the Photon Factory in High Energy Accelerator Research Organization (KEK). The total energy resolutions were estimated to be 0.20 eV for photon energy of hv = 630 eV. Photoelectron emission angles were changed from the surface normal to 60° for enhancement of surface sensitivity. To analyze in-depth profiles from angle-resolved core-level photoemission spectra measured by tilting the samples, the maximum entropy method, which was coded according to previous reports, was utilized. The validity of the in-depth profiles was confirmed by comparison with Rutherford backscattering spectroscopy (RBS). In-depth profile of the HfSiO film presents a complicated layer structure even at the as-grown stage; Si concentrations are high in both surface and interface regions and nitrogen atoms are slightly distributed at the interfacial layer. Accumulation of Si atoms at the surface is known by the ALD growth and the in-depth profile in the as- grown sample is quantitatively confirmed by RBS measurements. It should be noted that changes in the in-depth profiles suggest that Si oxide components diffuse from the interfacial SiOxNy layer into the HfSiO layer and concentrations of Hf relatively decrease. Coordination number obtained by Fourier transform of the EXAFS spectra decreases with increasing annealing temperature, suggesting that chemical bonding states on nearest neighbor of the Hf atoms in the HfSiO layer change with Si diffusion due to oxidation of the Si substrate.