Electrical characterization of HfO₂/4H-SiC and HfO₂/Si MOS structures

As the device size continues to shrink, the gate oxygen layer in MOS devices continues to become thinner, which leads to problems such as increased leakage current in conventional Si MOS devices. SiC, an important semiconductor material used in high-power devices, is not immune to the problem of premature breakdown due to the gate oxygen layer. Based on this, this paper adopts the innovative approach of replacing the conventional SiO2 as the gate oxygen layer with the high-k material, hafnium dioxide (HfO2), and continues the in-depth study on the electrical characteristics of the gate oxygen structure. In this paper, hafnium dioxide (HfO2) thin films were deposited on SiC and Si substrates using the atomic layer deposition(ALD) method. The metal-insulated semiconductor (MIS) structures with Al as the upper and lower electrodes were prepared, and the leakage currents and breakdown voltage characteristics of the MOS capacitors on the two different substrates were investigated. The leakage current density of the MOS capacitor structure with SiC substrate is 10-11 A/cm2,and the breakdown voltage is about 32 V. Based on the capacitance-voltage (C-V) measurements, the frequency dependence of the movable charge at the interface of the MOS capacitor structure is investigated. The lowest interfacial defect density (Dit) of the MOS capacitive structure with SiC substrate is only of the order of 1010 eV-1cm-2, while the movable charge Neff of the oxide layer of this sample is also controlled to the order of 1013 cm-2. It is worth mentioning that the HfO2/SiC structure performs better than the HfO2/Si structure in these electrical parameters, and the sample designed in this paper also performs better in electrical parameters than previous studies. These results undoubtedly demonstrate that the combination of High-k material (HfO2) and SiC in the MOS gate oxygen layer is a promising research topic.