Microstructural Observation of Focused Ion Beam Modification of Ni Silicide/Si Thin Films

Abstract

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 by 4 and 9 by 9 μm were patterned at room temperature with a 25keV 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 several precipitates appear around the treated area. Precipitates was analyzed by energy dispersive X-ray spectroscopy (EDS). Larger amount of Ni than the surrounding matrix was found in precipitates. Selected area diffraction (SAD) patterns of the precipitates and the corresponding dark field images imply the formation of a Ni rich silicide. The relation between the FIB tail and the precipitation is indicated.