Abstract
When the channel length of the MOSFET is scaled below 0.1 μm and SiO2 gate oxide thickness below 1.5 nm, tunneling current will increase significantly. Zirconium oxide (ZrO2) is considered as a potential replacement of SiO2. In this thesis, metal-insulator-semiconductor (MIS) capacitors, and MOSFETs with ZrO2 gate dielectrics were fabricated. The temperature dependence of the conduction current for Al/ZrO2/p-Si MIS capacitors was studied. With the Al electrode biased negative, the conduction mechanisms are found to be: (1) modified Schottky emission; (2) modified Poole-Frenkel emission; (3) Fowler-Nordheim tunneling; and (4) tunnel emission of trapped electrons under different temperature and electric field regions. The related electrical parameters are extracted from the I-V characteristics. The transistor properties were characterized. The IDS-VDS and IDS-VGS characteristics were measured. The degradation of electron mobility was studied. The temperature dependence of the electron mobility on vertical field reveals that Coulomb scattering, surface roughness scattering and phonon scattering of ZrO2-gated n-MOSFETs are more severe than that of SiO2-gated n-MOSFETs in the temperature range from 300 K to 420 K. Transverse soft optical phonons was used to explain the extra source of phonon scattering in ZrO2-gated n-MOSFETs. The interface trapped charge density, the surface recombination velocity, and the minority carrier lifetime in the field-induced depletion region measured from gated diodes were 5.79×1012 cm-2-eV-1, 941 cm/s, and 1.32×10-6 sec, respectively. A comparison with MOSFETs using SiO2 and Ta2O5 gate oxides was made. In summary, the conduction mechanisms in ZrO2 thin films were analyzed. The degradation of electron mobility was studied. The parameters in the field-induced depletion region of the ZrO2 gated diodes were obtained.