The electrical and materials properties of～20nm nickel silicide films, formed at 300℃, on n+/p and p+/n junctions are investigated. The sheet resistance of the silicide on p+/n junctions is found to be more than twice as high as that of the silicide on n+/p junctions. Cross section transmission electron microscopy, Rutherford backscattering spectroscopy, and x-ray photoelectron energy spectroscopy reveal that a pure Ni2Si layer forms on n+/p junctions while a thicker Ni2Si/NiSi double layer (～60% Ni2Si) forms on p+/n junctions. But the electrical differences are found to correlate only with differences in grain size and dopant concentration in the silicide.

The temperature-dependent current-voltage (I-V-T) technique has been used to study the Ni/Si solid phase reaction by measuring the Schottky barrier height (SBH) inhomogeneity of Ni-silicide/Si Schottky diodes. The experimental results show the strong dependence of SBH inhomogeneity on the Ni/Si solid phase reaction. The SBH distribution of the diodes annealed at 500 and 600℃ can be described by a single-Gaussian function and the diode annealed at 500℃ is found to have the best homogeneity and the smallest leakage current. The SBH distribution of the diodes annealed at 400, 700, and 800℃ can be described by a double-Gaussian function in which the mean value of the second Gaussian function is substantially smaller than that of the dominant Gaussian function. The variation of SBH inhomogeneity, an interface property, is related to the phase evolution process in the Ni/Si solid phase reaction, and verified by reverse I-V measurements. Our results indicate that the I-V-T technique may be developed as a wafer-level testing tool to monitor the silicidation process in the complementary metal-oxide-semiconductor device fabrication.

The Schottky contact of Co, its silicide and germanosilicide on n-poly-Si0.84Ge0.16 layer, was investigated. Amorphous Si0.84Ge0.16 layer was deposited on n-Si (100) substrate by ion beam sputtering (IBS). The layer was doped through thermal diffusion of phosphorus to fabricate n-poly-Si0.84Ge0.16 thin film. The Schottky diodes were formed by deposition of Co on n-poly-Si0.84Ge0.16 by the IBS technique. Solid-phase reaction between Co and n-poly-Si0.84Ge0.16 by rapid thermal annealing (RTA) as a function of temperature was studied. Phase identification and atomic depth profile were characterized by x-ray diffraction and Auger electron spectroscopy, respectively. The current-voltage and capacitance-voltage characteristics of both as-deposited and annealed Co/n-poly-Si0.84Ge0.16 Schottky diodes were investigated. The results reveal that the Schottky barrier height (SBH) keeps nearly constant with the annealing temperature between 300 and 600℃. The constancy of the SBH confirms the fact that Co and its silicides contacting with the same semiconductor have the close Schottky barrier height.

Thermal stability, phase and interface uniformity of Ni-silicide are some key issues for NiSi Salicide technology. The improved stability of NiSi was achieved by Ni/Pt/Si and Ni/Pd/Si reaction. The increase of thermal stability can be explained by classical nucleation theory. The phase and interface uniformity of Ni-silicides formed by Ni-Si solid-state reaction were characterized by X-ray diffraction (XRD) and temperature-dependent current-voltage (I-V-T) techniques. Results show that the Schottky barrier height (SBH) inhomogeneity characteristic has strong dependence on annealing temperature for Ni-silicide formation. Deep level transient spectroscopy (DLTS) measurement shows that annealing at relatively low temperature may cause electrically active deep level defects in the film. These results show that choosing a proper annealing temperature for Ni/Si silicidation will be very important for device performance.

Reaction characteristics of ultra-thin Ni films (5nm and 10nm) on undoped and highly doped (As-doped and B-doped) Si (100) substrates are investigated in this work. The sheet resistance (Rs) measurements confirm the existence of a NiSi salicidation process window with low Rs values within a certain annealing temperature range for all the samples except the one of Ni (5nm) on P+-Si (100) substrate (abnormal sample). The experimental results also show that the transition reaction to low resistivity phase NiSi is retarded on highly doped Si substrates regardless of the initial Ni film thickness. Micro-Raman and x-ray diffraction (XRD) measurement show that NiSi forms in the process window and NiSi2 forms in a higher temperature annealing process for all normal substrates. Auger electron spectroscopy (AES) results for the abnormal sample show that the high resistivity of the formation film is due to the formation of NiSi2.