Influence of Structural Variation of Ni Silicide Thin Films on Electrical Property for Contact Materials

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Abstract
The influence of crystallographic structural variation of Ni silicide thin films on the sheet resistance with annealing has been investigated. The agglomeration of NiSi and the phase transition to NiSi2 which occurred in the polycrystalline NiSi films have been revealed microscopically. It is found that degradation of the sheet resistance characteristic critically depends on the annealing time particularly at temperatures ranging from 650°C to 750°C. The enlargement of the Si-exposed region concomitant with the agglomeration of NiSi grains is a dominant factor responsible for the increase in sheet resistance and the activation energy of this process is estimated to be 2.8±0.4 eV. Furthermore, it is observed that the growth of epitaxial NiSi2 is initiated at the site where the agglomeration of NiSi grains results in the exposure of Si surfaces. The formation of the NiSi2 layer effectively suppresses the degradation of the film above 750°C.