Abstract
In this work, the electrical properties of HfO2 thin films as function of temperature were investigated. The temperature range is from 77 K to 465 K. Al/HfO2/p-Si metal-oxide-silicon (MOS) capacitors were fabricated. The HfO2 gate dielectrics were deposited by RF magnetron sputtering. The leakage current of Al/HfO2/p-Si MOS capacitors was about 10-6 A/cm2 at 1V in accumulation mode. The dominant conduction mechanism is Schottky emission at high temperatures ( 450 K) and low electric fields ( 2.2 MV/cm). At 77 K, the conduction mechanism is Fowler-Nordheim tunneling at high electric fields ( 2.6 MV/cm). Both the intercept of the fitted Schottky emission line and the slope of the fitted Fowler-Nordheim tunneling line are functions of barrier height and electron effective mass in HfO2. An analysis of self-consistent iteration method was used to show that the extracted Al/HfO2 barrier-height and electron effective mass in the HfO2 film (equivalent oxide thickness=5.33 nm) are about 0.94 eV and 0.4m0, respectively. Secondary ion mass spectrometry (SIMS), X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA) and transmission electron microscope (TEM) images were used to examine the material properties. N-channel metal-oxide-semiconductor field effect transistors using HfO2 gate oxide were also fabricated. The IDS-VDS and IDS-VGS characteristics were measured. The threshold voltage was 1.1 V. The subthreshold swing was 241 mV/dec.. The ION/IOFF is about 104. Since St=2.3(kT/q)[1+(CD+Cit)/Cox], the interface trapped charge density Dit is 1.4 1013 cm-2-eV-1. In the future, MOSFETs with HfO2 gate oxide will be a promising candidate for future generations of MOSFETs.