Ta_2Si Thermal Oxidation: A Simple Route to a High-k Gate Dielectric on 4H-SiC

摘要

This work investigates the bulk properties, the surface morphology, and the electrical interfacial characteristics of the Ta_2O_5-based high-t dielectric (epsilon_r ~ 20) produced by Ta_2Si deposition and subsequent oxidation directly on 4H-SiC substrates in the oxidation temperature range 750-1050 deg C. Electron microscopy measurements show that this insulator layer consists of a combination of delta-Ta_2O_5 grains and amorphous SiO_2 intergrain channels. An interfacial SiO_2 based layer is also evidenced. The surface roughness of the insulator diminishes when oxidation temperature increases. Annealing in N_2 the dielectric layers improves the interface characteristics for samples oxidized at 850 and 950 deg C where 4H-SiC substrate oxidation is negligible.