T. Stark et al., Deriving the kinetic parameters for Pt-silicide formation from temperatureramped in situ ellipsometric measurements, THIN SOL FI, 358(1-2), 2000, pp. 73-79
Single-wavelength ellipsometry is employed to monitor in situ the reaction
of 23 nm platinum layers with Si(100) to form platinum silicides during hea
ting at constant rates up to 100 K/min. A previous study showed that by the
use of 'Kissinger' plots the activation energy of the intermediate silicid
e phase Pt2Si and that of the final PtSi can be determined with an accuracy
of 50 meV. It is the purpose of the present paper to extend the study one
step further and obtain also the pre-exponential growth factor by directly
modeling the evolution of the ellipsometric data as they were obtained duri
ng the temperature ramp. To do so, the chemical composition of the reaction
products and the thickness of the formed layers were identified at crucial
stages of the reaction via RES. Additionally, the optical constants of the
constituent phases Pt, Pt2Si and PtSi were calculated from spectroscopic e
llipsometry measurements in the range from 1.5 to 4.5 eV. With this input i
nformation the evolution of the ellipsometric angles during the reaction of
Pt and Si were modeled quantitatively. The analysis yields good fits to th
e data for different ramp rates with activation energies of 1.50 and 1.70 e
V and reaction coefficients of 37 and 27 cm(2)/s for the Pt/Si to Pt2Si and
Pt2Si to PtSi formation, respectively. A significant improvement of the fi
t is obtained when the activation energies are allowed to be distributed ab
out their mean value with a width of 47 meV. This distribution takes inhomo
geneities in the reaction process into account and leads to a broadening of
the reaction fronts. (C) 2000 Elsevier Science S.A. All rights reserved.