HRTEM CHARACTERIZATION OF THE NISI2 GROWTH INTO THE SI(111) SURFACE

Metal-semiconductor junctions have been fabricated by a solid state re action in a Ni-Ti-Si layered system with the Ti interlayer acting as a diffusion barrier controlling the silicide forming reaction [1]. it h as been shown, that annealing between 450 and 475 degrees 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 wi dely extended cross-section TEM samples providing electron transparenc y over more than 100 mu m which allows imaging and analysis of the gro wing phases. Obviously, the extension of the epitaxially grown NiSi2 p latelets is dependent on the exact orientation of the silicon waver su rface. The position of the initial wafer surface is marked by an about 15 nm thick amorphous layer in ail investigated samples. The composit ion of this layer was determined to be Ti with a low concentration of silicon and a shortage of nickel as compared with the neighboring crys talline TixNiy and NixSiy layers. This composition suggests that this amorphous interlayer should play an important role for controlling the nickel silicide growth rate.