Abstract
The stability and composition of the Ni–germanosilicided films formed on relaxed
Si
1−x
Ge
x
alloy has been studied in the temperature range of 400–900 °C. During the solid phase thermal reaction between Ni and
Si
1−x
Ge
x
,
a nickel–germanosilicide
Ni
y
(
Si
1−w
Ge
w
)
1−y
ternary phase
(w⩽x
and
y≈0.5)
and a Ge-rich
Si
1−z
Ge
z
phase
(z>x)
have been found. In the lower annealing temperature range of
500 °
C
,
the Ge composition in the nickel–germanosilicide phase is similar to that of the
Si
0.75
Ge
0.25
substrate. At the same time, germination of
Si
1−z
Ge
z
(z>x)
takes place within the germanosilicide film. At higher annealing temperatures, Ni thermodynamically prefers to react with Si compared to Ge, and as a result, Ge segregates out from the germanosilicide grains to enrich Ge in the formed
Si
1−z
Ge
z
(z>x)
grains in between the germanosilicide grains. On the other hand, the size of the germanosilicide grains increases almost linearly with annealing temperature while that for the
Si
1−z
Ge
z
grains remains almost constant up to an annealing temperature of
700 °
C
,
and above which it increases sharply. As a result, the Ge-rich
Si
1−z
Ge
z
grains make the germanosilicide film discontinuous, leading to an increase in the sheet resistance of the germanosilicide film.