Study of Ni–Si thin-film interfacial reactions by coupling differential scanning calorimetry measurements and transmission electron microscopy analyses

In this paper, the solid-state interactions between a 500 nm thick Ni layer and a Si wafer are studied for temperatures up to 500 °C by coupling Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM). The phase transformation temperatures determined by DSC are about 250, 300, 350 and 410 °C. Dedicated samples were prepared to identify phase transformations occurring during heating up to these temperatures. TEM analyses show that the reaction product always consists of a continuous layer so that the nature of phase(s) formed at the interface can be determined. The reaction layer thickness is about 25, 50 and 150 nm for samples heated to 250, 300 and 350 °C, respectively. Moreover, from TEM diffraction patterns, it is shown that, for such a thick layer of Ni deposited on Si substrate, the first phase forming at the Ni/Si interface is the metastable Ni3Si compound.