FORMATION OF NI SILICIDE FROM NI(AU) FILMS ON (111)SI

The solid state reaction between a Ni (7 at. % Au) film and a Si subst rate at temperatures ranging from 250 to 800 degrees C is examined by scanning electron microscopy, x-ray diffraction, and Rutherford backsc attering spectrometry. Compared to the usual features for thin film re action of Ni with Si, we observed the following. (i) The simultaneous growth of Ni2Si and NiSi, and the growth of NiSi at the expense of bot h Ni2Si and Ni. This is related to Au accumulation in the metal layer. (ii) Au precipitation at 300 degrees C followed by the dissolution of the clusters thus created above the Au-Si eutectic temperature (370 d egrees C). (iii) A decrease of the temperature of formation of NiSi2 a nd the appearance of thickness oscillations that are characteristic of nucleation. These different effects are interpreted by taking into ac count the metallurgy of the system: segregation of Au in the Ni film, Au solubility in the different silicides, change in surface and interf ace energies, and chemical interactions with Si. (C) 1996 American Ins titute of Physics.