Atomic Layer Deposition of Al2O3 Thin Films for Metal Insulator Semiconductor Applications on 4H-SiC

This work reports on the growth and characterization of Al2O3 films on 4H-SiC, by Plasma Enhanced-Atomic Layer Deposition (PE-ALD). Different techniques were used to investigate the morphological, structural and electrical features of the Al2O3 films, both with and without the presence of a thin SiO2 layer, thermally grown on the 4H-SiC before ALD. Capacitance-voltage measurements on MOS structures resulted in a higher dielectric constant (e~8.4) for the Al2O3/SiO2/SiC stack, with respect to that of the Al2O3/SiC sample (e~ 6.7). Moreover, Current density-Electric Field measurements demonstrated a reduction of the leakage current and an improvement of the breakdown behaviour in the presence of the interfacial thermally grown SiO2. Basing on these preliminary results, possible applications of ALD-Al2O3 as gate insulator in 4H-SiC MOSFETs can be envisaged.