Solid-state reactions in Ti/Ni thin film system on silicon single crystal

Solid-state reactions in 200 nm Ti/200 nm Ni thin film system on (001) Si wafer have been investigated by X-ray diffraction, cross-sectional transmission electron microscopy (XTEM), and electrical resistance measurement. The purpose of work is to find out the influence of a superficial layer of Ti on the stability of NiSi formation. Samples were annealed at the temperature range from 470 to 1270K for 1 hour. X-ray diffraction was used for phase identification. XTEM, transmission electron microscopy (TEM) and four-point probe electrical resistance measurements were used to study morphology and microstructure changes. We found that after annealing at 470K, the amorphous particles having size of 200 nm appear. At annealing up to 670K they begin to crystallize into the NiSi phase. At the same time the intermetallic Ni₃Ti is formed. After annealing at 1070K for 1 hour the NiSi persists without transition to NiSi₂. The low resistivity of NiSi (9 μΩ·cm) does not change even after annealing at 1070K for 2 hours and demonstrated the stability of NiSi. After annealing at 1270K for 1 hour, both NiSi and NiSi₂ can be observed with the aid of X-ray diffraction. Nevertheless, electrical resistivity of the sample has only slightly increased to about 11 μΩ·cm, showing that NiSi is still the predominant phase.