Study On The Preparation And Characteristics Of HfAlO/SiC MOS Structure

Silicon carbide,the third generation wide bandgap semiconductor material, has many excellent properties,such as wide bandgap,high critical breakdown electric field and high thermal conductivity. SiC can be used to manufacture high-voltage and high-power devices.According to Gauss theorem(ksicESiC=koxideEOxide),the electric field in gate dielectric layer is inversely proportional to its dielectric constant.For SiO2gate dielectricis, the value of electric field in SiO2is as2.5times as SiC.So,the high-k matterials as gate dielectric material in SiC MOS power devices, such as HfO2, AL2O3, HfAlO or ZrO2, have atracted more and more atttention receently.In this paper, the4H-SiC MOS structures with HfO2, A12O3, HfAlO high-k dielectrics have been studied in detail. The influences of the Hf and A1component on the4H-SiC MOS structures are also discussed. The samples were tested with ellipsometer,XPS and high-frequency C-V.Dielectric constants,Interface states,boundary trap densities and conduction band offset are extracted. Research shows that the dielectric constant, interface state densities and conduction band offset reduce as Hf component down,and boundary trap densities increase while Hf component get down.The reasons are analysed based on the size of Al-O, Hf-O binding energy.The influences of annealing have been researched.Testing results show that the surface gets smooth and consistent. Because of reduction of Si unsaturated bond and oxygen vacancies,the samples have lower interface state densities and lower boundary trap densities.However, the conduction band offset of HfAlO gets down,It can be improved with buffer layer.