Performance Comparison of Al2O3 Gate Dielectric Grown on 4H-SiC Substrates via Thermal and Plasma-Enhanced Atomic Layer Deposition Methods

This study systematically compared the material and electrical properties of Al2O3 films deposited on n-type 4H-SiC substrates using thermal and plasma-enhanced atomic layer deposition (ALD), referred to as PE-Al2O3 and T-Al2O3, respectively. Atomic force microscopy data indicates that the roughness of Al2O3 deposited on SiC substrates by both ALD procedures is low. X-ray photoelectron spectroscopy analysis suggests that the proportion of hydroxides on T-Al2O3 surfaces is greater than that on PE-Al2O3. Based on O 1s energy loss spectra and fitting of absorption spectra, the bandgap of Al2O3 films ranges from 6.1 to 6.2 eV, with PE-Al2O3 exhibiting a slightly higher bandgap. As for C-V data analysis of MOS capacitors, PE-Al2O3/SiC possesses a lower interface defect density and border traps in oxide layer than T-Al2O3/SiC. Further I-V testing demonstrates that the breakdown field of PE-Al2O3 is 8.7 MV cm-1, with leakage current maintained at the order of 10-8 A cm-2. In contrast, T-Al2O3 displays a breakdown field of 7.2 MV cm-1 and a significant "soft" breakdown. The effective barrier height of PE-Al2O3/SiC is determined to be 1.10 eV based on Fowler-Nordheim tunneling mechanism fitting, which is greater than 0.952 eV for T-Al2O3. These results confirm the advantages of using the PEALD method.