| Summary: | 碩士 === 國立清華大學 === 物理學系 === 94 === Inelastic electron tunneling spectroscopy (IETS) in silicon metal-oxide-semiconductor systems with SiO2, pure HfO2, pure Y2O3, stacked Y2O3/HfO2, and stacked HfO2/Y2O3 as gate dielectrics have all been studied in this work. Information of electrode phonons, dielectric phonons, chemical bonding, and trap-related states in MOS structures has been able to be revealed by IETS. The bias polarity dependence of IETS has enabled the distinguishability to analyze microstructures either near the metal gate interface or near the silicon substrate interface. IETS results from HfO2 MOS tunnel junctions are consistent with published experimental and theoretical works relevant to Raman- and Infrared- active HfO2 phonon modes in monoclinic and tetragonal phases. IETS results of stacked Y2O3/HfO2 gate dielectrics, compared to pure HfO2, show less formation of hafnium silicate and less HfO2 and Y2O3 phonon peaks that can be detected with energies close to silicon phonons. Both phenomena observed are probably associated with less charge trapping and less ionic polarization of HfO2 and Y2O3 or intrinsically smaller ionic polarization of Y2O3 which may contribute to the improvement of channel carrier mobility due to suppressed coulomb scattering and reduced remote phonon scattering, respectively.
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