Electronic properties of ZrO2 films fabricated via atomic layer deposition on 4H-SiC and Si substrates

Abstract

Being an important semiconductor material for high power applications, silicon carbide (SiC) faces the problems while used as a gate oxygen layer in traditional Si MOS devices. In view of this, an innovative approach was adopted in the present work to replace the conventional SiO2 with a high-k material (ZrO2) as the gate oxygen layer to investigate its effect on the electrical characteristics of the devices. In particular ZrO2 films were deposited on Si and SiC substrates by atomic layer deposition (ALD), and Al was used as the electrode. The atomic force microscopy (AFM) microregion scan revealed a highly flat surface with Rq < 1 nm after the ALD growth of ZrO2 layer. The sample surface analysis via x-ray photoelectron spectroscopy (XPS) suggested the presence of a small amount of ZrOx components. According to the electron energy loss spectrum (EELS), the band gap width (Eg) of this ALD ZrO2 dielectric was 5.45 eV, which met the requirements for high-quality 4H-SiC-related MOS devices. The electrical properties of the samples were then studied, and the maximum breakdown voltage of the Al/ZrO2/SiC/Al MOS structure was obtained to be 23 V, i.e., nearly twice that of the Si substrate. As for the oxide layer, the interface defect density (Dit) near the conduction band of the Al/ZrO2/SiC/Al MOS structure was only 1012 eV−1 cm−2 orders of magnitude. The Neff value (the movable charge) of the structure was also controlled at 1012 cm−2. Therefore, the overall performance of the ZrO2/SiC structure in terms of electrical properties exceeded that of the ZrO2/Si structure and previously reported counterparts. In this respect, the ZrO2/SiC MOS capacitor structure has great research potential.