HRTEM characterization of the NiSi2 growth into the Si(111) surface

Metal-semiconductor junctions have been fabricated by a solid state reaction in a NiTiSi layered system with the Ti interlayer acting as a diffusion barrier controlling the silicide forming reaction [1]. It has been shown, that annealing between 450 and 475°C for about 30 min leads to laterally extended about 60 nm thick epitaxially grown NiSi2 with low contact resistivity. We have succeeded in preparing widely extended cross-section TEM samples providing electron transparency over more than 100 μm which allows imaging and analysis of the growing phases. Obviously, the extension of the epitaxially grown NiSi2 platelets is dependent on the exact orientation of the silicon waver surface. The position of the initial wafer surface is marked by an about 15 nm thick amorphous layer in all investigated samples. The composition of this layer was determined to be Ti with a low concentration of silicon and a shortage of nickel as compared with the neighboring crystalline TixNiy and NixSiy layers. This composition suggests that this amorphous interlayer should play an important role for controlling the nickel silicide growth rate.