Preparation Of Ni-based 4H-SiC Contact With Uniform Schottky Barrier

Silicon carbide(SiC),as a third-generation semiconductor material,is considered to be one of the indispensable materials for the development of devices suitable for extreme environments due to its excellent properties of high temperature resistance and high voltage resistance in the future.The quality of metal-semiconductor contact directly affects the application of the device,where the barrier non-uniformity presented in the Schottky contact hinders the widespread use of related devices such as Schottky diodes.In recent years,researchers have explored the mechanism of SiC Schottky barrier inhomogeneity from the surface and interface,and proposed ways to improve.In this paper,the formation mechanism of Ni/SiC SBH heterogeneity is studied from the interface microscopic point of view,and corresponding improvement schemes are proposed.The main research results are as follows:The experimental results showed that the deposited Ni/4H-SiC SBD has a uniform barrier height,but the barrier was not uniform after annealing at different temperatures,especially the barrier inhomogeneity of the 600?C annealed SBD was most obvious.The difference between the low barrier and the high barrier was 0.52 eV.After removing the Schottky contact layer,scanning electron microscopy(SEM)and atomic force microscopy(AFM)showed the SBD had hexagonal pits in the interface,which the lateral dimension were between 290 nm and 540 nm and the longitudinal(along the c-axis)is in the range of 24 nm to 45 nm.This indicate that the interfacial reaction has obvious non-uniform characteristics.The results from conductive atomic force microscopy(CAFM)have shown that the hexagonal pits had a lower barrier height than other regions.Therefore,the Ni/SiC barrier inhomogeneity is related to the non-uniform interfacial reaction,which provides theoretical guidance for improving the barrier non-uniformity.Based on the mechanism of barrier heterogeneity,the Ni/SiC barrier inhomogeneity was improved by W/Ni bimetal structure and intercalation Si,respectively.The study found that both effectively improved the barrier uniformity of Ni/SiC SBD.The effects of W and intercalated Si were characterized by SEM,AFM,transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).When annealing,W(Si)and part of Ni interdiffused(reacted)reducing the degree of reaction between Ni and SiC,improving surfacial and interfacial roughness of the sample.Therefore,both methods can eliminate the non-uniformity of Ni-based SiC barrier and have important application value.