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Title: Deposition and material characterisation of alternative high-K gate oxides
Author: Chen, B. P.-T.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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This thesis investigates the relation between the growth process, structure and properties of three potential high dielectric constant (high-K) gate oxides as replacements for silicon dioxide (SiO2) in Complementary Metal-Oxide-Semiconductor (CMOS) process. Production of high quality high-K gate oxides requires optimisation of the deposition conditions. Zirconium dioxide (ZrO2), yttria-stabilised ZrO2 (YSZ) and hafnium oxide (HfO2) films have been deposited using reactive radio-frequency (RF) magnetron sputtering in an Oxygen (O2)/ Argon (Ar) mixture at room temperature. The as-deposited film properties are quite comparable to those reported in the literature. ZrO2 exhibits a refractive index (R.I.) of 2.03, a bandgap of 5.8 eV, a dielectric constant of 26.2 and average breakdown field strength of 5.2 MV/cm. YSZ has a R.I. of 2.19, a bandgap of 5.6 eV, a dielectric constant of 27 and average breakdown field strength of 5.4 MV/cm. HfO2 possesses a R.I. of 2.1, a bandgap of 6 eV, a dielectric constant of 25 and average breakdown field strength of 5.4 MV/cm. Although the film qualities of all three oxide systems are similar, the research demonstrated that HfO2 is a better candidate to succeed thermal oxide as alternative gate dielectrics because the leakage current of HfO2 is at least seven orders in magnitude lower than that of using pure silicon oxide with identical equivalent oxide thickness (EOT). Electron Spin Resonance (ESR) studies of ZrO2 and YSZ films showed that defect trapping centres existed in the dielectrics. Initial investigation on potential metal nitride electrodes showed that surface oxidation is a major concern. This may be caused by exposure to air during the transfer to X-ray Photoelectron Spectroscopy (XPS) system or problems in the deposition procedure. The Ultraviolet Photoelectron Spectroscopy (UPS) analysis of the metal nitride reflects the material dependence of the work function and may be used as a guide in the future development of a suitable metal electrode.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available