Development of High Energy Photoelectron Spectroscopy and Its Application to Analyses of Chemical States at High-κ dielectric/Silicon Interface

Electron energy analyzer (R4000-10 keV, Gammadata Scienta Co.) dedicated for hard X-ray photoelectron spectroscopy (HX-PES) was developed. Using this analyzer with energy resolution of 45 meV and X-ray with photon energy by of 5.95 keV at undulator beam line BL29XU and BL47XU, which has full width half maximum of 60 meV, photoelectron spectroscopy can be achieved with total resolution of 75 meV (E/ΔE=79,000). Then, the following problems were found : 1)Analyzer could not be used for HXPES excited by 8 keV photons, 2)Power supply was unstable, etc. After these problems were solved, HX-PES with total energy resolution of 75 meV was achieved at hv=8 keV and 90 meV at hv=10 keV. Using this HX-PES system, the thermal stability of LaO_x/Si interface, which will be used as gate insulator in future generation of CMOS devices, was studied by measuring 5.95 keV photons' excited angle-resolved La 3d, Si 1s and O is photoelectron spectra at BL47XU. Si 1s spectra arising from La silicate formed at LaO_x/Si interface were found to appear if this interface was annealed in nitrogen gas under atmospheric pressure at temperature above 400℃. The depth profile of composition and chemical structures of LaO_x/Si structure were determined by applying maximum entropy concept to angle-resolved La 3d, Si 1s and O 1s spectra. Here, the compositional depth profile determined by high resolution Rutherford backscattering was used as a starting compositional depth profile. From these analyses, the thickness of LaO_x/Si interfacial transition layer was found to increase by annealing this interface above 400℃.