Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity
. Investigated in this work were changes in the concentration of charge carriers ne and their mobilities u, which occur under the influence of thermoannealing of n - Si and n - Ge crystals grown by the Czochralski method. Thermoannealing of n - Si samples was carried out both at 450 °C and 650 °C...
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Baranskii, P.I. Gaidar, G.P. 2017-05-29T16:43:47Z 2017-05-29T16:43:47Z 2012 Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity / P.I. Baranskii, G.P. Gaidar // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 3. — С. 218-222. — Бібліогр.: 24 назв. — англ. 1560-8034 PACS 61.82.Fk https://nasplib.isofts.kiev.ua/handle/123456789/118307 . Investigated in this work were changes in the concentration of charge carriers ne and their mobilities u, which occur under the influence of thermoannealing of n - Si and n - Ge crystals grown by the Czochralski method. Thermoannealing of n - Si samples was carried out both at 450 °C and 650 °C. The results of the influence of twostage (combined) thermoannealing have been presented. In the first series of experiments, the annealing was performed at 450 °C with varied duration (from 5 to 45 h) at the beginning, and then it was carried out for 40 hours at 650 °C. The second series of experiments was as follows: the annealing at 450 °C for 45-hour duration, then the annealing at 650 °C, which was carried out for various periods of time (5, 10, 20, 45, 66 hours). The observations for changes of ne and u were carried out both at the temperature 300 and 77 K. It is ascertained that changing the main parameters (ne and u) in n Ge As heavily doped single crystals, as a result of the series of thermoannealings (duration 30 min in each case) within the temperature range from 540 to 900 °C, is non-monotonous due to transformation of the thermodonors TD - I into TD-II . en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity Article published earlier |
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Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity |
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Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity Baranskii, P.I. Gaidar, G.P. |
| title_short |
Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity |
| title_full |
Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity |
| title_fullStr |
Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity |
| title_full_unstemmed |
Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity |
| title_sort |
peculiarities of thermoannealing in n-si and n-ge crystals with oxygen impurity |
| author |
Baranskii, P.I. Gaidar, G.P. |
| author_facet |
Baranskii, P.I. Gaidar, G.P. |
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2012 |
| language |
English |
| container_title |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| format |
Article |
| description |
. Investigated in this work were changes in the concentration of charge carriers
ne and their mobilities u, which occur under the influence of thermoannealing of n - Si
and n - Ge crystals grown by the Czochralski method. Thermoannealing of n - Si
samples was carried out both at 450 °C and 650 °C. The results of the influence of twostage
(combined) thermoannealing have been presented. In the first series of
experiments, the annealing was performed at 450 °C with varied duration (from 5 to
45 h) at the beginning, and then it was carried out for 40 hours at 650 °C. The second
series of experiments was as follows: the annealing at 450 °C for 45-hour duration, then
the annealing at 650 °C, which was carried out for various periods of time
(5, 10, 20, 45, 66 hours). The observations for changes of ne and u were carried out both
at the temperature 300 and 77 K. It is ascertained that changing the main parameters (ne
and u) in n Ge As heavily doped single crystals, as a result of the series of
thermoannealings (duration 30 min in each case) within the temperature range from 540
to 900 °C, is non-monotonous due to transformation of the thermodonors TD - I into
TD-II .
|
| issn |
1560-8034 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/118307 |
| citation_txt |
Peculiarities of thermoannealing in n-Si and n-Ge crystals with oxygen impurity / P.I. Baranskii, G.P. Gaidar // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 3. — С. 218-222. — Бібліогр.: 24 назв. — англ. |
| work_keys_str_mv |
AT baranskiipi peculiaritiesofthermoannealinginnsiandngecrystalswithoxygenimpurity AT gaidargp peculiaritiesofthermoannealinginnsiandngecrystalswithoxygenimpurity |
| first_indexed |
2025-11-26T22:50:15Z |
| last_indexed |
2025-11-26T22:50:15Z |
| _version_ |
1850778998487908352 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
218
PACS 61.82.Fk
Peculiarities of thermoannealing in n-Si and n-Ge crystals
with oxygen impurity
P.I. Baranskii1, G.P. Gaidar2
1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
45, prospect Nauky, 03680 Kyiv, Ukraine
2Institute for Nuclear Research, NAS of Ukraine,
47, prospect Nauky, 03680 Kyiv, Ukraine
Е mail: gaydar@kinr.kiev.ua
Abstract. Investigated in this work were changes in the concentration of charge carriers
ne and their mobilities , which occur under the influence of thermoannealing of Sin
and Gen crystals grown by the Czochralski method. Thermoannealing of Sin
samples was carried out both at 450 °C and 650 °C. The results of the influence of two-
stage (combined) thermoannealing have been presented. In the first series of
experiments, the annealing was performed at 450 °C with varied duration (from 5 to
45 h) at the beginning, and then it was carried out for 40 hours at 650 °C. The second
series of experiments was as follows: the annealing at 450 °C for 45-hour duration, then
the annealing at 650 °C, which was carried out for various periods of time
(5, 10, 20, 45, 66 hours). The observations for changes of ne and were carried out both
at the temperature 300 and 77 K. It is ascertained that changing the main parameters (ne
and ) in AsGen heavily doped single crystals, as a result of the series of
thermoannealings (duration 30 min in each case) within the temperature range from 540
to 900 °C, is non-monotonous due to transformation of the thermodonors ITD into
IITD .
Keywords: silicon, germanium, oxygen, thermoannealing, thermodonor, the Hall effect,
carrier concentration, mobility.
Manuscript received 07.05.12; revised version received 30.05.12; accepted for
publication 14.06.12; published online 25.09.12.
1. Introduction
It is known [1] that the thermal treatment of silicon
crystals doped with oxygen within the temperature range
350 to 550 °С leads to formation of donor centers and
change in the resistance of samples. Having learned the
kinetics of thermodonor formation, Kaiser et al. [2, 3]
concluded that these centers have oxygen nature and
represent a complex containing four atoms of oxygen
(SiO4). The thermodonor properties were described in
detail in the review [4]. Investigations of the
thermodonor properties [1, 2] showed that their donor
activity disappears after a short annealing at the
temperatures above 550 °С. It was also observed [5] that
the further thermal treatment at higher temperatures
(550…800 °С) leads to the appearance of donor activity
again. In [6] it was shown that these donor centers (the
authors call them “new donors”) differed in many
properties from the thermodonors that are formed in a
lower temperature range (350…550 °С).
In the literature [7], the low-temperature
thermodonors are called the thermodonors I ( ITD ),
and the “new donors” – the thermodonors II ( IITD ).
In [6, 8–12], the influence of carbon impurities, as
well as the preliminary annealing of samples at
400…500 °С, on the formation of IITD was studied.
It follows from the works [6, 8–11] that the preliminary
annealing at 400…500 °С of Si single crystals with the
low carbon content (NС < 316 cm10 ), as well as the
presence of this impurity in the bulk of silicon in the
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
219
appreciable amounts (NС < 316 cm102 ), promotes the
process of the formation of IITD . On the other hand,
the high content of carbon impurities in Sі (NС
316 cm102 ) complicates the generation of ITD [13].
In addition, the reduction of the ionization energy of
ITD with increasing the annealing time was
found [14].
For the last few decades, scientists of the world
have been shown great interest to the properties of Sі
crystals doped with oxygen. And these studies have been
still far from completed. For a long time the
thermodonors have been actively studied using different
techniques: the Hall effect [10, 14–16], the electron
paramagnetic resonance (EPR) [7, 17, 18], deep level
transient spectroscopy (DLTS) [19–21], infrared
spectroscopy [22, 23], photoluminescence [15] and
others. However, despite the large number of studies
[24], up to date an exact model of the donor center,
which could describe all the existing experimental data,
has not been developed.
2. Experimental
For the experiments with thermoannealing (TA) the
dislocation-free single crystals of Sin , doped with
phosphorus and grown by the Czochralski method, were
used. The content of doping and residual impurities in
the investigated crystals is presented in Table 1.
A higher concentration of oxygen in the ingot 2
provided a higher concentration of ITD (as compared
to the ingot 1) after the thermoannealings at 450 °C
( ITA ) of equal duration (see Table 2) as well as in the
growing process itself. The resistivity in the ingot 2
was 10 Ohmcm just when the growing process had been
over, however, proceeding from the calculation of the
quantity of added phosphorus as electrically active
impurity, it could have been expected about 35 Ohmcm.
After the 16-h annealing of the ingot 2 at 450 °С, the
carrier concentration increased up to
n300K 315 cm017.5 (300К 0.9 Оhmсm). To achieve
the value of n300K 314 cm015.1 (300K 28 Оhmсm,
which is close to the calculated value), the ingot 2
needed to be annealed for 1 hour at 650 °С. This value
n300K 314 cm015.1 was taken as the initial one and
related to the phosphorus dopant in the ingot 2.
Table 1. The content of main impurities in the crystals of n
– Si. Т = 300 K.
Doping concentration N, сm-3
Ingot
Phosphorus Oxygen Carbon
1 2.45 × 1014 5.1 × 1017 3.8 × 1016
2 1.50 × 1014 9.5 × 1017 3.0 × 1016
The carrier concentration (ne) in the ingot 1
corresponded to the calculated value. This fact and,
perhaps, a lower concentration of oxygen in the ingot 1
(in comparison with that of the ingot 2) provided a
higher stability of the ingot 1 with respect to the
thermoannealing at 650 °С ( IITA ) (see Table 2),
although the carbon content in both ingots was almost
identical.
3. Two-stage thermoannealing of n-Si samples with a
different content of oxygen impurity
The abovementioned thermal stability of the ingot 1 with
respect to IITA (at 650 °С) was lost after its
preliminary annealing (during 10–45 h) at 450 °С (see
Tables 3 and 4). These results show that, at lower
concentration of carbon atoms in the crystal
(NC 316 cm1043 ), the ITD , which are formed
during the low-temperature annealing of silicon crystals
(doped with oxygen) at the temperature about 450 °С,
most likely serve as the nucleation centers of IITD .
Indeed, as seen from the Table 3, a significant change in
the concentration of ne is observed after the
thermoannealing for 10 h at 450 °С
The two-stage thermoannealing changes not only
the concentration of the electrically active thermodonors,
which is evidenced by the change in the carrier
concentration ne as compared with ne in the initial
sample, but with the increase of ITA time qualitative
changes occur in the characteristic of newly-formed
thermocentres, as it is evidenced by the change in their
ability to ionization with increasing the ITA time, as
well as the growth of the ratio K77/K300 ee nn
from 1 to 1.14 (see Table 3).
The appearance and growth of EPR-activity in
thermodonors with increasing the IITA time is also of
great interest (see the data in column 7 of Table 4). This
fact also indicates that the increase of the IITA time
(which followed the ITA , Table 4) led not only to
quantitative but also to qualitative changes of the
thermodonors, which arose (and formed) as a result of
the combined thermal treatments
[( ITA ) + ( IITA )].
The latent period for the formation of the
nucleation centers of IITD at low-temperature
annealing (at the temperature close to 450 °С) is no less
than 5 h, as seen from the Table 3. While EPR-activity
in the studied samples appeared only after IITA , the
duration of which was t 10 hours (see Table 4,
columns 6 and 7).
It should be noted that ITD under the normal
conditions (i.e., when the crystal is free of any
impurities) do not show EPR-activity, which is evidently
explained by the presence of their double charge. In
contrast with ITD , IITD show the EPR-activity
that is clearly seen from the data of Table 4.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
220
Table 2. Influence of the annealing at various temperatures on the electrophysical properties of n – Si samples. The
time of thermoannealings (I and II) is approximately the same.
Annealing at 450 °С (TA-I) Annealing at 650 °С (TA-II)
300 K 77 K 300 K 77 K
Ingot
Annealing
time (hour) ne10-14,
сm-3
10-3,
сm2/(Vs)
ne10-14,
сm-3
10-3,
сm2/(Vs)
ne10-14,
сm-3
10-3,
сm2/(Vs)
ne10-14,
сm-3
10-3,
сm2/(Vs)
0 2.55 1.790 2.58 18.2 2.56 1.790 2.58 18.2
1 3.07 1.790 2.72 17.8 2.22 1.310 2.31 17.6
5 4.01 1.720 2.92 18.0 2.44 1.740 2.47 18.2
10 6.08 1.770 3.66 17.9 2.47 1.660 2.46 17.6
20 8.61 1.630 4.37 16.4 2.35 1.790 2.40 18.2
45 12.70 1.550 5.43 15.0 2.44 1.740 2.47 18.2
І
66 19.00 1.140 6.82 12.3 – – – –
0 1.5 1.590 1.20 17.4 1.5 1.590 1.26 17.4
1 3.18 1.480 1.98 15.2 1.87 1.670 1.79 15.7
2 5.16 1.440 2.70 14.5 2.81 1.530 2.17 15.5
3 8.66 1.330 3.49 14.4 3.22 1.430 2.56 14.6
5 12.8 1.430 4.7 14.3 8.45 1.300 5.32 13.2
10 24.9 1.400 7.11 14.0 16.9 1.320 8.73 12.0
15 38.8 1.220 10.5 11.66 25.0 1.350 7.80 12.0
45 83.6 1.180 18 10.6 33.6 1.170 7.14 10.8
ІІ
101 – – – – 32.0 1.160 6.40 10,6
Table 3. Influence of the time of preliminary annealing on the results of the two-stage thermal treatment of n – Si
samples prepared from the ingot 1.
Time of 1-st stage of
ТA at 450 °С, hour
(TA-I)
Time of 2-nd stage of
ТA at 650 °С, hour
(TA-II)
300 K
ne10-14, сm-3
77 K
ne10-14, сm-3
300 K
n10-13, сm-3
5 2.44 2.44 0
10 2.87 2.80 4.2
20 3.07 2.85 6.2
45 3.35 2.95 9.0
Initial sample
40
2.45 2,45 –
4. Influence of thermoannealings
(at Тann = 540…900 °С) applied to heavily doped
single crystals of n – Ge As on the change in
concentrations of charge carriers and their mobilities
The investigation of changes in the concentrations of
charge carriers ne and their mobilities as a result of
thermoannealings of AsGen single crystals grown
by the Czochralski method at various temperatures
(when the annealing time in all the cases was 30 min)
was carried out. Cooling the crystals to room
temperature was achieved by simple turning-off the heat
source. The obtained results that are summarized in
Table 5 showed that changes of the main parameters (ne
and ) in the heavily doped samples of AsGen with
an increase of Тann from 540 up to 900 °С are not
monotonous. Certainly, because after some decrease of
ne, related to the thermoannealing within the range
600…725 °С of ITD , formed in the crystal with the
residual oxygen impurity at the temperature range
500…540 °С, the concentration ne begins to increase due
to transition into the temperature range 830…900 °С.
In this range, the so-called IITD are formed from
atomic oxygen appeared as a result of ITD decay.
This transformation of ITD into IITD is observed
in oxygen impurity rich crystals (exactly these samples
were used in these experiments).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
221
Table 4. Data obtained after two-stage thermal treatment of n – Si. The samples were prepared from the ingot 1.
ЕPR
ТDN
Stage of ТA Тann, °С
Time of
ТA t,
hour
300 K
ne10-14,
сm-3
77 K
ne10-14,
сm-3
ЕPR
Р
ЕPR
ТD
N
N ЕPR
ТDN 10-3 сm-3
300 K
n10-13,
сm-3
1 2 3 4 5 6 7 8
Initial
sample
– – 3.0 3.0 0 0 0
Stage 1 450 45 12.7 5.43 0 0 97
5 3.02 2.76 0 0 0.2
10 3.05 2.79 0.02 0.6 0.5
20 3.62 3.10 0.165 5.0 6.2
45 4.75 3.33 0.423 13.0 17.5
Stage 2 650
66 6.19 3.06 – – 31.9
Table 5. Changes in the concentrations of charge carriers ne and their mobilities as a result of thermoannealings of
heavily doped samples of n – GeAs grown by the Czochralski method at various temperatures (the annealing time in
all the cases was 30 min).
State of sample Changes of ne after ТA
Number
of sample
Initial (In)
Conditions of ТA:
Тann, °С; t = 0.5 h
Charge carrier
concentration
ne 10–19,
сm–3
Charge carrier
mobility ,
сm2/(Vs)
n0
Changes (),
no changes (0)
In 3.57 322 n01
540 °С 3.57 310 no changes (0)
In 3.85 286 n02
600 °С 3.51 300 decreases (–)
In 3.90 270 n03
640 °С 3.15 290 decreases (–)
In 4.00 278 n04
725 °С 4.00 263 no changes (0)
In 4.02 272 n05
800 °С 4.56 246 increases (+)
In 4.00 280 n06
830 °С 4.87 230 increases (+)
In 3.88 292 n07
900 °С 4.68 248 increases (+)
Note. Temperature of measurements was 293…300 K.
It should be noted that the atoms of background
impurities (oxygen, hydrogen, nitrogen or helium) in the
lattice of silicon and germanium are the defects that can
directly or indirectly (due to creating the local
mechanical strains) affect the properties of crystals. The
significant concentration of oxygen impurity
(NО 31817 cm102105 ) in the ingots, pulled out
from the melt, as well as the ability of this impurity to
transform into the electrically active state during
thermoannealing, led to the need to study in detail the
behaviour of the ITD and IITD .
5. Conclusions
In the oxygen-containing single crystals n – Si and
n – Ge, transformation of thermodonors TD – I into
TD – II during the change of thermoannealing regimes,
which are widely used in the manufacture of
semiconductor devices, was investigated.
In crystals Sin that were characterized by the
different concentration of dopant (phosphorus) and
residual (oxygen and carbon) impurities, the influence of
low-temperature (450 °С) and high-temperature (650 °С)
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
222
thermoannealings on the change in the carrier
concentration was studied. It is shown that the results of
high-temperature thermoannealings (at 650 °С) with
different time duration depend significantly on the initial
state of the investigated crystals and on the specific
parameters of the low-temperature thermoannealing (at
450 °С), which was applied to the crystal before its high-
temperature thermal treatment.
In crystals of Gen , it was found that changing
the main parameters (concentrations of charge carriers ne
and their mobilities ) in heavily doped single crystals of
AsGen , grown by the Czochralski method, as a
result of the series of thermoannealings (for 30 min in
each case) within the temperature range from 540 up tо
900 °С is non-monotonous due to transformation of
ITD (appearing within the range 500…540 °С and
are annealed at 600…725 °С) into IITD , which were
formed from atomic oxygen appearing as a result of
ITD decay during transition within the temperature
range 830…900 °С.
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6600 (1983).
19. J.L. Benton, L.С. Kimerling, M. Stavola, The
oxygen related donor effect in silicon // Physica
B+C, 116 (1-3), p. 271-275 (1983).
20. P.M. Henry, J.W. Farmer, J.M. Meese, Symmetry
and electronic properties of the oxygen thermal
donor in pulled silicon // Appl. Phys. Lett. 45 (4),
p. 454-456 (1984).
21. W.W. Keller, Pressure dependence of oxygen-
related defect levels in silicon // J. Appl. Phys.
55 (10), p. 3471-3477 (1984).
22. B. Pajot, H. Compain, J. Lerouille, B. Clerjaud,
Spectroscopic studies of 450 °C thermal donors in
silicon // Physica B+C, 117-118 (1-3), p. 110-
112 (1983).
23. M. Stavola, K.M. Lee, J.C. Nabity, P.E. Freeland,
L.С. Kimerling, Site symmetry and ground-state
characteristics for the oxygen donor in silicon //
Phys. Rev. Lett. 54 (24), p. 2639-2642 (1985).
24. V.M. Babich, N.I. Bletskan, Е.F. Venger, Oxygen
in Silicon Single Crystals. Interpres LТD, Kiev,
1997 (in Russian).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 3. P. 218-222.
PACS 61.82.Fk
Peculiarities of thermoannealing in n-Si and n-Ge crystals
with oxygen impurity
P.I. Baranskii1, G.P. Gaidar2
1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
45, prospect Nauky, 03680 Kyiv, Ukraine
2Institute for Nuclear Research, NAS of Ukraine,
47, prospect Nauky, 03680 Kyiv, Ukraine
Е mail: gaydar@kinr.kiev.ua
Abstract. Investigated in this work were changes in the concentration of charge carriers ne and their mobilities (, which occur under the influence of thermoannealing of
Si
n
-
and
Ge
n
-
crystals grown by the Czochralski method. Thermoannealing of
Si
n
-
samples was carried out both at 450 °C and 650 °C. The results of the influence of two-stage (combined) thermoannealing have been presented. In the first series of experiments, the annealing was performed at 450 °C with varied duration (from 5 to 45 h) at the beginning, and then it was carried out for 40 hours at 650 °C. The second series of experiments was as follows: the annealing at 450 °C for 45-hour duration, then the annealing at 650 °C, which was carried out for various periods of time (5, 10, 20, 45, 66 hours). The observations for changes of ne and ( were carried out both at the temperature 300 and 77 K. It is ascertained that changing the main parameters (ne and () in
As
Ge
n
-
heavily doped single crystals, as a result of the series of thermoannealings (duration 30 min in each case) within the temperature range from 540 to 900 °C, is non-monotonous due to transformation of the thermodonors
I
TD
-
into
II
TD
-
.
Keywords: silicon, germanium, oxygen, thermoannealing, thermodonor, the Hall effect, carrier concentration, mobility.
Manuscript received 07.05.12; revised version received 30.05.12; accepted for publication 14.06.12; published online 25.09.12.
1. Introduction
It is known [1] that the thermal treatment of silicon crystals doped with oxygen within the temperature range 350 to 550 °С leads to formation of donor centers and change in the resistance of samples. Having learned the kinetics of thermodonor formation, Kaiser et al. [2, 3] concluded that these centers have oxygen nature and represent a complex containing four atoms of oxygen (SiO4). The thermodonor properties were described in detail in the review [4]. Investigations of the thermodonor properties [1, 2] showed that their donor activity disappears after a short annealing at the temperatures above 550 °С. It was also observed [5] that the further thermal treatment at higher temperatures (550…800 °С) leads to the appearance of donor activity again. In [6] it was shown that these donor centers (the authors call them “new donors”) differed in many properties from the thermodonors that are formed in a lower temperature range (350…550 °С).
In the literature [7], the low-temperature thermodonors are called the thermodonors
I
-
(
I
TD
-
), and the “new donors” – the thermodonors
II
-
(
II
TD
-
).
In [6, 8–12], the influence of carbon impurities, as well as the preliminary annealing of samples at 400…500 °С, on the formation of
II
TD
-
was studied. It follows from the works [6, 8–11] that the preliminary annealing at 400…500 °С of Si single crystals with the low carbon content (NС <
3
16
cm
10
-
), as well as the presence of this impurity in the bulk of silicon in the appreciable amounts (NС <
3
16
cm
10
2
-
×
), promotes the process of the formation of
II
TD
-
. On the other hand, the high content of carbon impurities in Sі (NС (
3
16
cm
10
2
-
×
) complicates the generation of
I
TD
-
[13]. In addition, the reduction of the ionization energy of
I
TD
-
with increasing the annealing time was found [14].
For the last few decades, scientists of the world have been shown great interest to the properties of Sі crystals doped with oxygen. And these studies have been still far from completed. For a long time the thermodonors have been actively studied using different techniques: the Hall effect [10, 14–16], the electron paramagnetic resonance (EPR) [7, 17, 18], deep level transient spectroscopy (DLTS) [19–21], infrared spectroscopy [22, 23], photoluminescence [15] and others. However, despite the large number of studies [24], up to date an exact model of the donor center, which could describe all the existing experimental data, has not been developed.
2. Experimental
For the experiments with thermoannealing (TA) the dislocation-free single crystals of
Si
n
-
, doped with phosphorus and grown by the Czochralski method, were used. The content of doping and residual impurities in the investigated crystals is presented in Table 1.
A higher concentration of oxygen in the ingot 2 provided a higher concentration of
I
TD
-
(as compared to the ingot 1) after the thermoannealings at 450 °C (
I
TA
-
) of equal duration (see Table 2) as well as in the growing process itself. The resistivity ( in the ingot 2 was 10 Ohm(cm just when the growing process had been over, however, proceeding from the calculation of the quantity of added phosphorus as electrically active impurity, it could have been expected about 35 Ohm(cm. After the 16-h annealing of the ingot 2 at 450 °С, the carrier concentration increased up to n300K (
3
15
cm
0
1
7
.
5
-
×
((300К ( 0.9 Оhm(сm). To achieve the value of n300K (
3
14
cm
0
1
5
.
1
-
×
((300K ( 28 Оhm(сm, which is close to the calculated ( value), the ingot 2 needed to be annealed for 1 hour at 650 °С. This value n300K (
3
14
cm
0
1
5
.
1
-
×
was taken as the initial one and related to the phosphorus dopant in the ingot 2.
Table 1. The content of main impurities in the crystals of n – Si. Т = 300 K.
Ingot
Doping concentration N, сm‑3
Phosphorus
Oxygen
Carbon
1
2.45 × 1014
5.1 × 1017
3.8 × 1016
2
1.50 × 1014
9.5 × 1017
3.0 × 1016
The carrier concentration (ne) in the ingot 1 corresponded to the calculated value. This fact and, perhaps, a lower concentration of oxygen in the ingot 1 (in comparison with that of the ingot 2) provided a higher stability of the ingot 1 with respect to the thermoannealing at 650 °С (
II
TA
-
) (see Table 2), although the carbon content in both ingots was almost identical.
3. Two-stage thermoannealing of n‑Si samples with a different content of oxygen impurity
The abovementioned thermal stability of the ingot 1 with respect to
II
TA
-
(at 650 °С) was lost after its preliminary annealing (during 10–45 h) at 450 °С (see Tables 3 and 4). These results show that, at lower concentration of carbon atoms in the crystal (NC (
(
)
3
16
cm
10
4
3
-
´
-
), the
I
TD
-
, which are formed during the low-temperature annealing of silicon crystals (doped with oxygen) at the temperature about 450 °С, most likely serve as the nucleation centers of
II
TD
-
. Indeed, as seen from the Table 3, a significant change in the concentration of ne is observed after the thermoannealing for 10 h at 450 °С
The two-stage thermoannealing changes not only the concentration of the electrically active thermodonors, which is evidenced by the change in the carrier concentration ne as compared with ne in the initial sample, but with the increase of
I
TA
-
time qualitative changes occur in the characteristic of newly-formed thermocentres, as it is evidenced by the change in their ability to ionization with increasing the
I
TA
-
time, as well as the growth of the ratio
(
)
(
)
K
77
/
K
300
e
e
n
n
from 1 to 1.14 (see Table 3).
The appearance and growth of EPR-activity in thermodonors with increasing the
II
TA
-
time is also of great interest (see the data in column 7 of Table 4). This fact also indicates that the increase of the
II
TA
-
time (which followed the
I
TA
-
, Table 4) led not only to quantitative but also to qualitative changes of the thermodonors, which arose (and formed) as a result of the combined thermal treatments [(
I
TA
-
) + (
II
TA
-
)].
The latent period for the formation of the nucleation centers of
II
TD
-
at low-temperature annealing (at the temperature close to 450 °С) is no less than 5 h, as seen from the Table 3. While EPR-activity in the studied samples appeared only after
II
TA
-
, the duration of which was t ( 10 hours (see Table 4, columns 6 and 7).
It should be noted that
I
TD
-
under the normal conditions (i.e., when the crystal is free of any impurities) do not show EPR-activity, which is evidently explained by the presence of their double charge. In contrast with
I
TD
-
,
II
TD
-
show the EPR-activity that is clearly seen from the data of Table 4.
ЕPR
ТD
N
4. Influence of thermoannealings
(at Тann = 540…900 °С) applied to heavily doped single crystals of n – Ge (As( on the change in concentrations of charge carriers and their mobilities
The investigation of changes in the concentrations of charge carriers ne and their mobilities ( as a result of thermoannealings of
As
Ge
n
-
single crystals grown by the Czochralski method at various temperatures (when the annealing time in all the cases was 30 min) was carried out. Cooling the crystals to room temperature was achieved by simple turning-off the heat source. The obtained results that are summarized in Table 5 showed that changes of the main parameters (ne and () in the heavily doped samples of
As
Ge
n
-
with an increase of Тann from 540 up to 900 °С are not monotonous. Certainly, because after some decrease of ne, related to the thermoannealing within the range 600…725 °С of
I
TD
-
, formed in the crystal with the residual oxygen impurity at the temperature range 500…540 °С, the concentration ne begins to increase due to transition into the temperature range (830…900 °С. In this range, the so-called
II
TD
-
are formed from atomic oxygen appeared as a result of
I
TD
-
decay. This transformation of
I
TD
-
into
II
TD
-
is observed in oxygen impurity rich crystals (exactly these samples were used in these experiments).
ЕPR
Р
ЕPR
ТD
N
N
It should be noted that the atoms of background impurities (oxygen, hydrogen, nitrogen or helium) in the lattice of silicon and germanium are the defects that can directly or indirectly (due to creating the local mechanical strains) affect the properties of crystals. The significant concentration of oxygen impurity (NО (
3
18
17
cm
10
2
10
5
-
´
-
´
) in the ingots, pulled out from the melt, as well as the ability of this impurity to transform into the electrically active state during thermoannealing, led to the need to study in detail the behaviour of the
I
TD
-
and
II
TD
-
.
5. Conclusions
In the oxygen-containing single crystals n – Si and
n – Ge, transformation of thermodonors TD – I into TD – II during the change of thermoannealing regimes, which are widely used in the manufacture of semiconductor devices, was investigated.
In crystals
Si
n
-
that were characterized by the different concentration of dopant (phosphorus) and residual (oxygen and carbon) impurities, the influence of low-temperature (450 °С) and high-temperature (650 °С) thermoannealings on the change in the carrier concentration was studied. It is shown that the results of high-temperature thermoannealings (at 650 °С) with different time duration depend significantly on the initial state of the investigated crystals and on the specific parameters of the low-temperature thermoannealing (at 450 °С), which was applied to the crystal before its high-temperature thermal treatment.
In crystals of
Ge
n
-
, it was found that changing the main parameters (concentrations of charge carriers ne and their mobilities () in heavily doped single crystals of
As
Ge
n
-
, grown by the Czochralski method, as a result of the series of thermoannealings (for 30 min in each case) within the temperature range from 540 up tо 900 °С is non-monotonous due to transformation of
I
TD
-
(appearing within the range 500…540 °С and are annealed at 600…725 °С) into
II
TD
-
, which were formed from atomic oxygen appearing as a result of
I
TD
-
decay during transition within the temperature range (830…900 °С.
References
1. C.S. Fuller, J.A. Ditzenberg, N.B. Hannay, E. Buehler, Resistivity changes in silicon induced by heat treatment // Phys. Rev. 96 (3), p. 833 (1954).
2. W. Kaizer, H.L. Frisch, H. Reiss, Mechanism of the formation of donor states in heat-treated silicon // Phys. Rev. 112 (5), p. 1546-1554 (1958).
3. W. Kaizer, Electrical and optical properties of heat-treated silicon // Phys. Rev. 105 (6), p. 1751-1756 (1957).
4. U. Gosele, T.Y. Tan, Oxygen diffusion and thermal donor formation in silicon // Appl. Phys. A: Mater. Sci. & Proc. 28 (2), p. 79-92 (1982).
5. P.М. Kurilo, Е. Sеitov, М.I. Khitren, Influence of thermal treatment on the electrical properties of n-Si, containing a high concentration of oxygen // Fizika i tekhnika poluprovodnikov, 4 (12), p. 2267-2270 (1970), in Russian.
6. A. Kanamori, M. Kanamori, Comparison of two kinds of oxygen donors in silicon by resistivity measurements // J. Appl. Phys. 50 (12), p. 8095-8101 (1979).
7. P.I. Baranskii, V.M. Babich, N.P. Baran, Yu.P. Dotsenko, V.B. Kovalchuk, V.A. Shershel, Investigation of formation conditions of thermal donors-I and -II in oxygen-containing n-type silicon within the temperature range 400 to 800 °C // Phys. stat. sol. (a), 78 (2), p. 733-739 (1983).
8. V. Cazcarra, P. Zunino, Influence of oxygen on silicon resistivity // J. Appl. Phys. 51 (8), p. 4206-4211 (1980).
9. K. Schmalz, P. Gaworzewski, On the donor activity of oxygen in silicon at temperatures from 500 to 800 °C // Phys. status solidi (a), 64 (1), p. 151-158 (1981).
10. P. Gaworzewski, K. Schmalz, On the kinetics of thermal donors in oxygen-rich silicon in the range from 450 to 900 °C // Phys. status solidi (a), 58 (2), p. K223-K226 (1980).
11. J. Leroueille, Influence of carbon on oxygen behavior in silicon // Phys. status solidi (a), 67 (1), p. 177-181 (1981).
12. Yu.M. Babitskii, P.М. Grinshtein, Е.V. Оrlova, Decay of the supersaturated solid solution of oxygen in silicon and thermodonors // Elektronnaya tekhnika. Ser. 6. Materialy. № 2, p. 33-37 (1982), in Russian.
13. A.R. Bean, R.C. Newman, The effect of carbon on thermal donor formation in heat treated pulled silicon crystals // J. Phys. Chem. Solids, 33 (2), p. 255-268 (1972).
14. P. Gaworzewski, K. Schmalz, On the electrical activity of oxygen in silicon // Phys. status solidi (a), 55 (2), p. 699-707 (1979).
15. H. Nakayama, J. Katsura, T. Nishino, Y. Hamakawa. Hall-effect and photoluminescence measurements of oxygen-related donors in CZ-Si crystals // Jpn. J. Appl. Phys. 19 (9), p. L547-L550 (1980).
16. P. I. Baranskii, V.M. Babich, N.P. Baran, A.A. Bugay, Yu.P. Dotsenko, V.B. Kovalchuk, The effect of heat treatment on compensated CZ silicon // Phys. status solidi (a), 82 (2), p. 533-536 (1984).
17. S.H. Muller, M. Sprenger, E.G. Sieverts, C.A.J. Ammerlaan, EPR spectra of heat-treatment centers in oxygen-rich silicon // Solid State Communs. 25 (12), p. 987-990 (1978).
18. M. Suezawa, K. Sumino, M. Iwaizumi, Electron spin resonance study of oxygen donors in silicon crystals // J. Appl. Phys. 54 (11), p. 6594-6600 (1983).
19. J.L. Benton, L.С. Kimerling, M. Stavola, The oxygen related donor effect in silicon // Physica B+C, 116 (1-3), p. 271-275 (1983).
20. P.M. Henry, J.W. Farmer, J.M. Meese, Symmetry and electronic properties of the oxygen thermal donor in pulled silicon // Appl. Phys. Lett. 45 (4), p. 454-456 (1984).
21. W.W. Keller, Pressure dependence of oxygen-related defect levels in silicon // J. Appl. Phys. 55 (10), p. 3471-3477 (1984).
22. B. Pajot, H. Compain, J. Lerouille, B. Clerjaud, Spectroscopic studies of 450 °C thermal donors in silicon // Physica B+C, 117-118 (1-3), p. 110-112 (1983).
23. M. Stavola, K.M. Lee, J.C. Nabity, P.E. Freeland, L.С. Kimerling, Site symmetry and ground-state characteristics for the oxygen donor in silicon // Phys. Rev. Lett. 54 (24), p. 2639-2642 (1985).
24. V.M. Babich, N.I. Bletskan, Е.F. Venger, Oxygen in Silicon Single Crystals. Interpres LТD, Kiev, 1997 (in Russian).
Table 4. Data obtained after two-stage thermal treatment of n – Si. The samples were prepared from the ingot 1.
Stage of ТA�
Тann, °С�
Time of ТA t,
hour�
300 K
ne(10�14, сm�3�
77 K
ne(10�14, сm�3�
� EMBED Equation.3 ����
300 K
(n(10�13, сm�3�
�
�
�
�
�
�
� EMBED Equation.3 ����
� EMBED Equation.3 ���(10�3 сm�3�
�
�
1�
2�
3�
4�
5�
6�
7�
8�
�
Initial sample�
–�
–�
3.0�
3.0�
0�
0�
0�
�
Stage 1�
450�
45�
12.7�
5.43�
0�
0�
97�
�
Stage 2�
650�
5�
3.02�
2.76�
0�
0�
0.2�
�
�
�
10�
3.05�
2.79�
0.02�
0.6�
0.5�
�
�
�
20�
3.62�
3.10�
0.165�
5.0�
6.2�
�
�
�
45�
4.75�
3.33�
0.423�
13.0�
17.5�
�
�
�
66�
6.19�
3.06�
–�
–�
31.9�
�
Table 5. Changes in the concentrations of charge carriers ne and their mobilities ( as a result of thermoannealings of heavily doped samples of n – Ge(As( grown by the Czochralski method at various temperatures (the annealing time in all the cases was 30 min).
Number
of sample�
State of sample�
Charge carrier concentration ne ( 10–19,
сm–3�
Charge carrier mobility (,
сm2/(V(s)�
Changes of ne after ТA�
�
�
Initial (In)
Conditions of ТA: �Тann, °С; t = 0.5 h�
�
�
n0
Changes ((),
no changes (0)�
�
1�
In�
3.57�
322�
n0�
�
�
540 °С�
3.57�
310�
no changes (0)�
�
2�
In�
3.85�
286�
n0�
�
�
600 °С�
3.51�
300�
decreases (–)�
�
3�
In�
3.90�
270�
n0�
�
�
640 °С�
3.15�
290�
decreases (–)�
�
4�
In�
4.00�
278�
n0�
�
�
725 °С�
4.00�
263�
no changes (0)�
�
5�
In�
4.02�
272�
n0�
�
�
800 °С�
4.56�
246�
increases (+)�
�
6�
In�
4.00�
280�
n0�
�
�
830 °С�
4.87�
230�
increases (+)�
�
7�
In�
3.88�
292�
n0�
�
�
900 °С�
4.68�
248�
increases (+)�
�
Note. Temperature of measurements was 293…300 K.
Table 2. Influence of the annealing at various temperatures on the electrophysical properties of n – Si samples. The time of thermoannealings (I and II) is approximately the same.
Ingot�
Annealing time (hour)�
Annealing at 450 °С (TA-I)�
Annealing at 650 °С (TA-II)�
�
�
�
300 K�
77 K�
300 K�
77 K�
�
�
�
ne(10�14, сm�3�
((10�3, сm2/(V(s)�
ne(10�14, сm�3�
((10�3, сm2/(V(s)�
ne(10�14, сm�3�
((10�3, сm2/(V(s)�
ne(10�14, сm�3�
((10�3, сm2/(V(s)�
�
І�
0�
2.55�
1.790�
2.58�
18.2�
2.56�
1.790�
2.58�
18.2�
�
�
1�
3.07�
1.790�
2.72�
17.8�
2.22�
1.310�
2.31�
17.6�
�
�
5�
4.01�
1.720�
2.92�
18.0�
2.44�
1.740�
2.47�
18.2�
�
�
10�
6.08�
1.770�
3.66�
17.9�
2.47�
1.660�
2.46�
17.6�
�
�
20�
8.61�
1.630�
4.37�
16.4�
2.35�
1.790�
2.40�
18.2�
�
�
45�
12.70�
1.550�
5.43�
15.0�
2.44�
1.740�
2.47�
18.2�
�
�
66�
19.00�
1.140�
6.82�
12.3�
–�
–�
–�
–�
�
ІІ�
0�
1.5�
1.590�
1.20�
17.4�
1.5�
1.590�
1.26�
17.4�
�
�
1�
3.18�
1.480�
1.98�
15.2�
1.87�
1.670�
1.79�
15.7�
�
�
2�
5.16�
1.440�
2.70�
14.5�
2.81�
1.530�
2.17�
15.5�
�
�
3�
8.66�
1.330�
3.49�
14.4�
3.22�
1.430�
2.56�
14.6�
�
�
5�
12.8�
1.430�
4.7�
14.3�
8.45�
1.300�
5.32�
13.2�
�
�
10�
24.9�
1.400�
7.11�
14.0�
16.9�
1.320�
8.73�
12.0�
�
�
15�
38.8�
1.220�
10.5�
11.66�
25.0�
1.350�
7.80�
12.0�
�
�
45�
83.6�
1.180�
18�
10.6�
33.6�
1.170�
7.14�
10.8�
�
�
101�
–�
–�
–�
–�
32.0�
1.160�
6.40�
10,6�
�
Table 3. Influence of the time of preliminary annealing on the results of the two-stage thermal treatment of n – Si samples prepared from the ingot 1.
Time of 1-st stage of ТA at 450 °С, hour (TA-I)�
Time of 2-nd stage of ТA at 650 °С, hour (TA-II)�
300 K
ne(10�14, сm�3�
77 K
ne(10�14, сm�3�
300 K
(n(10�13, сm�3�
�
5�
40�
2.44�
2.44�
0�
�
10�
�
2.87�
2.80�
4.2�
�
20�
�
3.07�
2.85�
6.2�
�
45�
�
3.35�
2.95�
9.0�
�
Initial sample�
�
2.45�
2,45�
–�
�
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
218
ЕPR
ТD
N
_1406122169.unknown
_1406197451.unknown
_1406198582.unknown
_1406198823.unknown
_1406203234.unknown
_1406203768.unknown
_1406203780.unknown
_1406204470.unknown
_1406203777.unknown
_1406203731.unknown
_1406202286.unknown
_1406203187.unknown
_1406202283.unknown
_1406202223.unknown
_1406198746.unknown
_1406198791.unknown
_1406198586.unknown
_1406197470.unknown
_1406198535.unknown
_1406197456.unknown
_1406123390.unknown
_1406124573.unknown
_1406126086.unknown
_1406126257.unknown
_1406197407.unknown
_1406126319.unknown
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