TEM observation of FIB induced damages in Ni2Si/Si thin films

Focused ion beam (FIB) irradiation of a thin Ni2Si layer deposited on a Si substrate was carried out and studied using an in-situ transmission electron microscope (in-situ TEM). Square areas on sides of 4.5 by 4.5 and 9 by 9 mu m were patterned at room temperature with a 25 keV Ga+-FIB attached to the TEM. The structural changes of the films indicate a uniform milling; sputtering of the Ni2Si layer and the damage introducing to the Si substrate. Annealing at 673 K results in the change of the Ni2Si layer into an epitaxial NiSi2 layer outside the FIB irradiated area, but many dislocations and precipitates appear inside the treated area. Ion beam mixing of Ni into the substrate was shown by energy dispersive X-ray spectroscopy (EDS). A considerable amount of Ni and a small amount of Ga were found in precipitates, while only Si was detected outside the precipitates in the irradiated area. Selected area diffraction (SAD) patterns of the precipitates and the corresponding dark field images imply the formation of a Ni rich silicide which contains a small amount of Ga.