Phase transformations at a nickel–silicon interface under transient annealing

We use intense incoherent light pulses of ~60 μs duration to induce reactions at a Ni–Si interface. Changes in morphology, composition, and electrical characteristics of the interfaces are studied. The diagnostics include scanning electron microscopy, Auger spectroscopy, X-ray analysis, and diffusion analysis. After annealing for a total of ~1 ms, the Si surface is found to support an intermixed and disordered Ni–Si layer consisting of mixed islands and flat structures. On further irradiation, after a certain threshold Ni density is reached in the Si, silicide growth takes place at the interface through an amorphous-to-crystalline transformation of this intermixed layer. The first phase to nucleate is mononickel silicide with a (200) orientation. This is attributed to kinetic effects, which optimize the heat of formation in the presence of excess Si.