Electron tunneling spectroscopy of silicon metal-oxide-semiconductor system with thin gate dielectric.

摘要

The objectives of this dissertation research are to demonstrate tunneling spectroscopy as a viable technique for gate dielectric study and to apply this technique to characterize MOS systems with advanced gate dielectrics. The dielectrics studied include thermal silicon oxide (SiO2), silicon nitride (Si3N4) and hafnium oxide HfO2 made by Jet-Vapor-Deposition (JVD) process.; Utilizing this non-invasive technique, we have observed vibrational modes which provide chemical bonding and composition information of thin gate dielectrics. Detailed changes in the MOS material system resulting from different processes are revealed by the variations of the tunneling spectra. The bias polarity dependence of tunneling spectroscopy enables the differentiation of microstructures either near the gate electrode interface or near the silicon substrate interface.; Applying IETS as a method to monitor electron-phonon scattering near the gate dielectric and substrate interface is suggested. Relatively low energy phonons ("soft phonons") of HfO2 observed in IETS spectrum suggest the possibility of electron scattering by HfO2 phonons in the MOS structure, which limits carrier mobility in MOSFET with high-K dielectrics.; Tunneling spectroscopy study of trap-related defects in the gate dielectrics is also reported in the dissertation. Tunneling spectroscopy reveals defect structures not only by detecting electrons interacting with defect vibration modes, but also by detecting electrons tunneling via localized defect states or traps. Using the trap feature appearing in both voltage polarities, a method for determining trap energy and physical location within the dielectric is developed. The tunneling spectroscopy technique is used to characterize trap-related defects for MOS structure with HfO2 as gate dielectric deposited by JVD process.