This paper discusses the results of cross-sectional transmission electron microscopy (TEM) based investigation of nickel silicide (NiSi) thin films grown on silicon. Nickel silicide is currently used as the CMOS technology standard for local interconnects and in electrical contacts. In addition to high resolution imaging, the analysis of these films also utilized other TEM-based techniques which consisted of energy filtered imaging, energy dispersive X-ray analysis (EDX), electron energy loss spectroscopy (EELS), selected-area electron diffraction (SAED), and hollow cone illumination (HCI).

The nickel silicide thin films were formed by vacuum annealing thin films of nickel (50 nm) deposited on (100) silicon. The cross-sectional samples indicated a final silicide (metal-silicon reaction product) thickness of about 115 nm. This investigation studied and reports on three aspects of the thermally formed thin films: the uniformity in composition of the film using EDX; the crystalline orientation of the thin films using SAED and HCI; the quality and nature of the interface using a combination of high resolution imaging, SAED, EELS, and EDX.

The analysis highlighted uniform composition in the thin films, which was also substantiated by spectroscopy techniques; desired and preferential crystalline orientation corresponding to stoichiometric NiSi, supported by glancing angle X-ray diffraction results; and an interface exhibiting the desired abrupt transition from silicide to silicon. Analysis was carried out to confirm the absence of oxygen at the interface, as the presence of oxygen affects the electrical conductivity of the films and increases the resistance posed by the silicide-silicon interface to electrical current.

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