Preparation of uniform contact-interface applying nanocrystalline silicide with controlled crystalline grain size

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We have examined the formation of a uniform NiSi/Si contact-interface by reducing its crystalline grain size under the appropriate preparation conditions. It is revealed that the temperature during Ni sputter-deposition on the heated Si substrate and that during the following annealing process are important to reduce the crystalline grain size. Under a certain temperature, the growth of NiSi2, a high temperature phase, occurs at a lower temperature, resulting in the degradation of the uniform interface. It is speculated that the low temperature formation of NiSi2 is owing to the formation of an interdiffused Ni-Si layer with a concentration gradient of Ni, in which NiSi2 will nucleate from an alloy region in a Si-rich composition. We confirm the NiSi2 formation in the system of Ni on SiO2/Si, in which the Ni diffusion through a thin SiO2 layer reduces the diffusivity of Ni species, resulting in the formation of a Si-rich Ni-Si alloy from which NiSi2 will nucleate.