Abstract
Abstract N-channel metal-oxide-semiconductor field effect transistors (MOSFETs) using HfO2 gate oxide were fabricated successfully. The HfO2 films were deposited by RF magnetron sputtering. The C-V, ID-VD and ID–VG characteristics are measured. The minimum threshold voltage was 0.67 V~0.74V. The minimum subthreshold swing was 71.6 mV/dec. The ION/IOFF ratio is about 106 at VD=0.05 V, which indicates that the HfO2 MOSFETs have good current switch capability. Since St=2.3(kT/q)[1+(CD+Cit)/Cox], the interface trapped charge density Dit is extracted to be about 2.61x1012 cm-2-eV-1. The dielectric constant measured from a separate metal-HfO2-silicon capacitor is 19.31. Al/HfO2/p-Si metal-insulator-silicon (MIS) capacitors were also fabricated to characterize the electrical properties of the HfO2 dielectric. The electrical conduction mechanisms of HfO2 thin film as functions of temperature were studied. The temperature range is from 300 to 578O K. The leakage current density is -9.96×10-6A/cm2 when the applied voltage is -1 V and the HfO2 thickness is 20.2 nm. At more high electrical field (0.6MV/cm~1.1MV/cm) and High temperature (>513OK) with the Al electrode biased both at negative and positive, the conduction mechanism of Al/HfO2 and HfO2/Si interface is Schottky Emission. The A.E.S, SIMS, XRD, SEM, AFM analyses were made. 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 1.6x1013 cm-2-eV-1, 2568 cm/s, and 1.63x10-8 sec, respectively. A comparison with MOSFETs using SiO2 and Ta2O5 gate oxides was made. The HfO2/Si interface is generally inferior compared with that of the SiO2/Si interface. But the HfO2/Si interface is comparable to that of the Ta2O5/Si interface. The thermodynamic stability of HfO2 gate oxide is much better than that of Ta2O5 date oxide. In the future, MOSFETs with HfO2 gate oxide will be a promising candidate for sub-0.1 um MOSFETs.