Grain boundary reactive diffusion during Ni2Si formation in thin films andits dependence on the grain boundary angle

The process of reactive diffusion of Ni in thin films is studied during the low temperature (250 degrees C < 300 degrees C) growth of Ni2Si on Si(100) and Si(111) substrates. The silicide on the Si(lll) substrates presents te xtured structures which probably involves mainly low-angle(< 15 degrees) gr ain boundaries, whereas the grains of the silicide on the Si(100) substrate s do not show texture correspondingly presenting a random predominantly hig h-angle grain boundary distribution. Assuming Ni grain boundary diffusion b eing the dominant limiting process of the solid-state reaction, the corresp onding grain boundary reactive diffusion coefficient is determined from the kinetics of the silicide formation. It is observed that the coefficient be longing to low-angle boundaries is smaller than that measured in randomly d istributed high-angle boundaries and they are determined to be D-gb =1.74 X 10(-2) exp (- 1.22/kT) cm(2)/s and D-gb = 7.45 X 10(-1) exp(-1.35/kT) cm(2 )/s, respectively. The results indicate similarity between normal and react ive diffusion processes. (C) 1999 Elsevier Science B.V. All rights reserved .