Direct observation of interfacial reaction of Ni/6H-SiC and carbon redistribution by in situ transmission electron microscopy

Abstract

The interfacial reaction of Ni/SiC has been attracting considerable attention because SiC substrate has excellent chemical and thermal stability and low electrical resistivity, which are essential properties for various device applications. However, research on the initial reaction at low temperature and exact mechanism is currently insufficient. Therefore, we investigated the reaction of Ni films on a 6H-SiC substrate and the behavior of carbon at 550 °C by direct observation with transmission electron microscopy (TEM) during in situ heating. At 550 °C, the Ni31Si12 phase formed during the reaction of Ni and SiC. The Ni silicide layer thickened as the reaction front proceeded toward the 6H-SiC substrate and carbon atoms from decomposed SiC converted into graphite. In addition, carbon existed in three regions. First, carbon existed as graphite on the external surface of Ni silicide layer during initial reaction. Second, graphite formed at the original interface between the Ni film and the 6H-SiC substrate. Finally, carbon existed at the bottom of the Ni silicide region due to its low diffusivity in the silicide. The elemental distribution of Ni, Si, and C was observed in detail through various analytical techniques. We demonstrate the reaction mechanism of Ni and SiC at 550 °C and the distribution of carbon atoms.