Oxygen '96
Early Stages of Oxygen Precipitation in Silicon
ATOMIC COMPOSITION, STRUCTURE AND VIBRATIONAL EXCITATION OF
SUBSTITUTIONAL CARBON-OXYGEN COMPLEXES IN SILICON
H. Yamada-Kaneta
(a),
Y. Shirakawa (a) and
C. Kaneta
(b)
(a) Process Development Div. Fujitsu Ltd., 1015 Kamikodanaka,
Nakahara-ku, Kawasaki 211, JAPAN
(b) Electron Devices and Materials Laboratories, Fujitsu
Laboratories Ltd., 10-1, Morinosato-wakamiya, Atsugi 243-01,
JAPAN
The complexes of the substitutional carbon (Cs) and the
interstitial oxygen (Oi) are the nuclei that promote the
oxygen precipitation in silicon crystals. We investigated annealing
behaviour of the intensities of the infrared absorption peaks A, B,
B', C, C' and D of the Cs-Oi complexes observed
at 1104, 1052, 1099, 1112, 1026 and 1108 cm-1,
respectively. In the early stage of the annealing, we found a
quasi-thermal-equilibrium state in which the concentration of the
(Cs)m-(Oi)n complexes
(m, n : numbers of the carbon and oxygen atoms) are dominated
by the mass-action law
[(Cs)m-(Oi)n] = kappa(T)
[Cs]m[Oi]n. kappa(T) is an
equilibrium reaction constant for the annealing temperature T. From
the observed correlation between the peak intensities and the obtained
formulas of the mass-action law (i.e. values of n), we found the
following: The peaks A and D are due to the
(Cs)1-(Oi)1 complex(es);
the peaks B and B' are due to the
(Cs)1-(Oi)2 complex; and
the peaks C and C' are due to the
(Cs)1-(Oi)3 complex.
For the peaks A, D, B and C, the measured temperature dependence of
the intensity were somewhat weak, but similar to that of the 1136
cm-1 peak of the isolated Oi. This indicates
that the Oi in the complexes causing these peaks still has
the 2-dimensional low-energy anharmonic excitation (2D LEAE) similar
to that of isolated Oi. The weakened temperature dependence
however suggests the weakened off-axis nature of the Oi
causing these peaks. On the other hand, the intensities of the
lower-energy peaks B' and C' hardly exhibited temperature dependence,
implying that the Oi's causing these peaks no longer have
the 2D LEAE and the off-centre nature. In other words, for the peak at
the lower energy, the responsible Oi has the weaker
off-axis nature. This tendency is explained by the expansion of the
Si-Si distance of the Si-O-Si unit in the complex. From these
arguments and the previous findings in the ab initio
calculation, we speculate the possible atomic structures for the
identified (Cs)1-(Oi)n
complexes.
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Last modified: Mon Feb 19 12:10:48 GMT 1996
JG
