Nitrogen Doping and Thermal Stability in HfSiOxNy Studied by Photoemission and X-ray Absorption Spectroscopy Page: 3 of 11

                                
investigate these problems from the viewpoint of chemical bonding states. In the
previous report, we found that it is possible to detect the silicidation8 and
crystallization9 separately in HfO2/Si by photoemission and XAS. In this letter, we
discuss chemical bonding states of nitrogen atoms in HfSiOXNy fabricated by
N2-plasma nitridation of HfSiOX and their thermal stability in terms of silicidation and
crystallization.
HfSiOx films were grown on the chemical and ozone oxidized Si(001) substrates
in Ar/02 atmosphere using atomic-layer-deposition (ALD) techniques. HfSiOXNy films
were prepared by nitridation treatment of HfSiOX using N2-plasma at room
temperature. Details about the sample growth procedures were reported in ref. 10. The
thicknesses of these films were measured as double-layer structures with the top
HfSiOx(Ny) layer of 1.4 nm and the interfacial Si02 layer of 2.6 nm by cross-sectional
transmission electron microscope (TEM). We prepared two films of HfSiOXNy with y=0
and 0.2 in order to investigate the N2-plasma nitridation effects.
Photoemission and x-ray absorption spectroscopy (XAS) were carried out at
beam line 10.1 of Stanford Synchrotron Radiation Laboratory (SSRL) in the Stanford
Linear Accelerator Center (SLAC) with photon energies ranging from 200 to 1000 eV.
The total energy resolutions were estimated to be 0.5 and 1.2 eV at the photon energies
(h ) of 210 and 640 eV, respectively, by Gaussian widths of Hf 4f photoemission spectra
in a metallic Hf silicide. The total-electron-yield method was used for N K-edge XAS.
Annealing was performed in ultrahigh vacuum by radiative heating from the backside
of the samples. The temperature at sample surfaces was monitored by a pyrometer.
Annealing was performed for 10 min at each temperature. Curve fittings for core-level

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