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 Al 2 O 3 films deposited on n-type 4H-SiC substrates using thermal and plasma-enhanced atomic layer deposition (ALD), referred to as PE-Al 2 O 3 and T-Al 2 O 3 , respectively. Atomic force microscopy data indicates that the roughness of Al 2 O 3 deposited on SiC substrates by both ALD procedures is low. X-ray photoelectron spectroscopy analysis suggests that the proportion of hydroxides on T-Al 2 O 3 surfaces is greater than that on PE-Al 2 O 3 . Based on O 1s energy loss spectra and fitting of absorption spectra, the bandgap of Al 2 O 3 films ranges from 6.1 to 6.2 eV, with PE-Al 2 O 3 exhibiting a slightly higher bandgap. As for C–V data analysis of MOS capacitors, PE-Al 2 O 3 /SiC possesses a lower interface defect density and border traps in oxide layer than T-Al 2 O 3 /SiC. Further I–V testing demonstrates that the breakdown field of PE-Al 2 O 3 is 8.7 MV cm −1 , with leakage current maintained at the order of 10 –8 A cm −2 . In contrast, T-Al 2 O 3 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-Al 2 O 3 . These results confirm the advantages of using the PEALD method.