3D imaging of backside metallization of SiC-SBD influenced by annealing

Abstract

In this study, the influence of annealing at 250 °C for 500 h on Ohmic contact of backside electrode of Silicon Carbide Schottky-Barrier-Diode (SiC-SBD) was investigated. Considering the prevalence status of the SiC-SBD as power device applications, the experiment was implemented on a commercial based SiC-SBD device. The annealing has brought remarkable transition in the structure and the impurity profile at the surface and the Ag/Ni interface of the device as a result of oxidation. For these evaluations, dual-beam Time-of-flight Secondary Ion Mass Spectrometry is regarded as an available analytical technique on the high sensitivity and imaging ability. In the deeper region of the backside electrode, an amorphous Ni–Ti alloy layer was found between the Ni/Ti interface of the annealed sample, which is also considered the result of diffusion due to the annealing. On the other hands, some nuggets of glassy-carbon and Ti cubic structures were observed in the Ni(Si)–C layer of both the non-annealed and the annealed samples. These structures are deduced to be formed during the fabrication process of the backside electrode and to be stable against the annealing. For these evaluations, Transmission Electron Microscopy (TEM) and Scanning TEM (STEM)—Energy Dispersion X-ray analysis were optimized with the high lateral resolution.