Characteristics of HfO2 Dielectric in Planar and Trench Structured SiC Capacitors

Silicon carbide (SiC) is extensively utilized in the power electronics industry due to its superior characteristics, such as high breakdown field strength, excellent thermal conductivity, and high electron saturation drift velocity. In particular, SiC MOSFETs, as a crucial power device, are progressively transitioning to trench structure designs to mitigate the impact of the JFET effect. Nonetheless, the critical breakdown field strength of SiC is higher than that of silicon, and the electric field concentration at the trench gate corner is more severe, raising concerns about the reliability of the gate oxide layer. This study delves into the suitability of $\text{HfO}_{2}$ as the gate oxide material in trench-structured SiC capacitors, aiming to promote its application in SiC trench MOSFETs. HfO2 films were successfully deposited on SiC epitaxial layers using atomic layer deposition (ALD) technology, and $\text{Al}/\text{HfO}_2/\text{SiC}/\text{Al}$ capacitors were constructed with aluminum serving as the top and bottom electrodes. The film growth on the silicon carbide surface was characterized in detail using Atomic Force Microscopy (AFM), spectroscopic ellipsometry (SE), and X-ray photoelectron spectroscopy (XPS). Comprehensive electrical testing was conducted, including capaci tance- vo ltage (C- V) and current-voltage (1-V) measurements, to evaluate leakage current, breakdown voltage, and interface trap density (Dit), thereby gaining a deeper understanding of the device's performance. In addition, this study also investigated the changes in HfO2 as the channel gate dielectric after rapid thermal annealing treatment at $300^{\circ} \mathrm{C}, 400^{\circ} \mathrm{C}$, and $500^{\circ} \mathrm{C}$ to explore the impact of this process on device characteristics. The objective of this research is to thoroughly investigate the applicability of HfO2 as the gate oxide material for trench-structured SiC capacitors, with the goal of advancing its real-world utilization in SiC trench MOSFET technology.