A model for non-thermal action of microwave radiation on oxide film/semiconductor structures
A model is considered that explains mechanism of non-thermal action of microwave radiation on the thin SiO₂ (ТiO₂, Er₂O₃, Gd₂O₃) film/SiC and SiO₂/GaAs structures. It assumes that the centers of electron-hole recombination are redistributed because of resonance interaction between dislocations of...
Saved in:
| Published in: | Semiconductor Physics Quantum Electronics & Optoelectronics |
|---|---|
| Date: | 2014 |
| Main Author: | |
| Format: | Article |
| Language: | English |
| Published: |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2014
|
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/118513 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures / O.B. Okhrimenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 3. — С. 227-231. — Бібліогр.: 26 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859743213140574208 |
|---|---|
| author | Okhrimenko, O.B. |
| author_facet | Okhrimenko, O.B. |
| citation_txt | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures / O.B. Okhrimenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 3. — С. 227-231. — Бібліогр.: 26 назв. — англ. |
| collection | DSpace DC |
| container_title | Semiconductor Physics Quantum Electronics & Optoelectronics |
| description | A model is considered that explains mechanism of non-thermal action of
microwave radiation on the thin SiO₂ (ТiO₂, Er₂O₃, Gd₂O₃) film/SiC and SiO₂/GaAs
structures. It assumes that the centers of electron-hole recombination are redistributed
because of resonance interaction between dislocations of certain length and microwave
radiation. As a result, additional bands appear in photoluminescence (PL) spectra of the
oxide film/SiC structures or intensities of some bands are redistributed in the PL spectra of
the SiO₂/GaAs structure, as well as optical density of the oxide film/SiC structures changes.
|
| first_indexed | 2025-12-01T19:42:06Z |
| format | Article |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
227
PACS 78.70.Fy, 78.70.Gq
A model for non-thermal action of microwave radiation
on oxide film/semiconductor structures
O.B. Okhrimenko
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prospect Nauky, 03028 Kyiv, Ukraine
Phone: 38(044) 525-62-61; fax: 38(044) 525-83-42; e-mail: olga@isp.kiev.ua
Abstract. A model is considered that explains mechanism of non-thermal action of
microwave radiation on the thin SiO2 (ТiO2, Er2O3, Gd2O3) film/SiC and SiO2/GaAs
structures. It assumes that the centers of electron-hole recombination are redistributed
because of resonance interaction between dislocations of certain length and microwave
radiation. As a result, additional bands appear in photoluminescence (PL) spectra of the
oxide film/SiC structures or intensities of some bands are redistributed in the PL spectra of
the SiO2/GaAs structure, as well as optical density of the oxide film/SiC structures changes.
Keywords: microwave radiation, dislocation, transmission spectrum, photo-
luminescence, silicon carbide.
Manuscript received 03.03.14; revised version received 21.07.14; accepted for
publication 16.09.14; published online 30.09.14.
1. Introduction
It is known that action of microwave radiation on device
structures and final products (diodes, transistors,
integrated circuits) often leads to their degradation and
catastrophic failures. There are literature data indicating
the effects of defect gettering and structural relaxation in
semiconductor materials induced by microwave
radiation. In those cases, attention is paid to non-thermal
nature of such actions as well as on processes induced by
them at the metalsemiconductor and insulator
semiconductor interfaces [1, 2] that are integral parts of
MIS transistor structures. At the same time, there is no
model in literature that could unambiguously explain
mechanism of non-thermal action on the oxide
layer/semiconductor structures.
In this work, a model is proposed that gives
consistent explanation for mechanism of non-thermal
action of microwave radiation on the thin oxide film SiO2
(ТiO2, Er2O3, Gd2O3)/SiC and SiO2/GaAs structures.
2. Experimental results
In experimental works [3-7] it was shown that a short-
term microwave annealing of frequency 2.45 GHz leads
to increase of optical transmission in thin oxide
film/silicon carbide structures (Fig. 1) and appearance of
additional bands in photoluminescence (PL) spectra of
similar structures (Fig. 2) or redistribution of PL bands
intensity, as in GaAs/SiO2 structures (Fig. 3).
It was shown in [1, 2, 8-12] that changes in
semiconductor defect subsystem under action of
microwave radiation may be of thermal as well as non-
thermal character. The thermal mechanisms of action of
microwave radiation may be classified into three groups
for convenience [8, 9]. One of the possible mechanisms
is related to dielectric polarization. Such type of action
of microwave field on dielectric materials involves the
following processes:
distortion of electron clouds of separate atoms;
generally the electron shells of many-electron
atoms (those of high atomic number) are easier
deformed (atoms are polarized easier);
alignment of molecules or structural elements with
a constant dipole momentum along the field lines;
deformation (variation of bond angle and length) of
molecules, both with and without dipole moment,
under action of a microwave field.
Another mechanism of action of microwave
radiation involves free-charge currents that are excited in
solids and contribute to heating because of ohmic losses.
This mechanism is typical for high-conduction solids. One
more mechanism to be accounted for is due to ohmic
losses related to eddy currents excited by magnetic fields.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
228
400 500 600 700 800
0
2
4
6
8
10
12
14
a
T
ra
ns
m
is
si
on
, %
Wavelength, nm
1
2
3
4
5
400 500 600 700 800
0
2
4
6
8
10
12
14
16
Wavelength, nm
b
T
ra
ns
m
is
si
on
, %
1
2
3
4
5
400 500 600 700 800
2
4
6
8
10
12
14
c
T
ra
n
sm
is
si
o
n
, %
Wavelength, nm
1
2
3
4
5
Fig. 1. Transmission spectra of the oxide film/SiC structures:
(a) TiO2, (b) Gd2O3, (c) Er2O3 taken before (1 – initial
structure) and after microwave annealing. Total time of
microwave annealing: 1 s (2), 2 (3), 3 (4), 8 (5) [6].
To determine the degree of thermal action of
microwave radiation on the specimens under
investigation, let us estimate temperature variation T
owing to such action. Since the oxide layer does not
absorb microwave radiation [13], the only source of
specimen heating is absorption of microwave radiation in
semiconductor. Let us assume that the specimen absorbs
the total microwave radiation, and the absorbed energy is
uniformly distributed over the specimen volume. Then the
highest possible temperature of heated specimen is
VС
E
T . (1)
Here V is the specimen volume (in our case. the
average specimen volume V = 0.0125 cm3); E = Wt is
the energy passing to the specimen in a time t, W = PV,
P is the microwave radiation power per specimen unit
volume (0.04 W/cm3); С() is SiC thermal capacity
(density): С = 620750 J/kgdeg = 0.620.75 J/gdeg
[14], = 3170 kg/m3 = 3.170 g/cm3 [14].
After inserting the above parameters to Eq. (1),
taking irradiation time to equal 1 s and assuming that the
total microwave radiation is absorbed by the specimen,
we obtain that its temperature may change by
T = 0.02 . Therefore, it is possible to neglect the
contribution from thermal mechanism when explaining
the observed variations of properties of metal oxide film
and silicon carbide at the film/SiC interface appearing
under microwave irradiation.
1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
P
L
in
te
n
si
ty
,
a
rb
.u
n.
Photon energy E, eV
1
2
3
4
Fig. 2. PL spectra of the oxide film/SiC structures taken before
(1 – initial structure) and after microwave annealing (2 –
TiO2/SiC, 3 – Gd2O3/SiC, 4 – Er2O3/SiC). Total time of
microwave annealing 8 s [6].
0.6 0.8 1.0 1.2 1.4 1.6
0
1
2
3
4
5
6
Photon energy E, eV
P
L
in
te
ns
ity
,
ar
b.
un
.
1
2
3
4
5
6
Fig. 3. PL spectra of the SiO2/GaAs structure taken on the side
of SiO2 film before (1 – initial structure) and after microwave
annealing (26). Total time of microwave irradiation:
1 min (2), 2 (3), 3 (4), 8 (5), 13 (6) [7].
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
229
3. Possible model for non-thermal action of
microwave radiation
A single quantum of microwave radiation of frequency
2.45 GHz is ~ eV10 5 . This is much below the activation
energy of migration for migration of inherent atoms,
their vacancies and impurity atoms in SiC (from 1.47 eV
[4] to 8 eV [15]) as well as phonon energy in silicon
carbide (~ eV1010010 3 [16]).
The most likely reason for appearance of non-
thermal effect of microwave radiation is presence in a
crystal of nonequilibrium states that cause sensitivity of
defect structure to action of microwave radiation. In
particular, it was noted in [17, 18] when considering
effect of low electric fields on nonmagnetic crystals that
such effect is just due to presence of structural defects in
them. It may be assumed that microwave field (as
magnetic field) can lower the potential barriers (related to
random distribution of the fields of intrinsic stresses in a
crystal) that must be surmounted to provide dislocation
movement [17, 18].
Besides, microwave radiation can affect not only
on the process of dislocation interaction with an obstacle
but on the structure of dislocation nuclei and obstacles as
well. The obstacles may be several impurity atoms and
cation vacancies as well as be of variable composition
[17, 18]. Relaxation of intrinsic stresses leads to inverse
effect, namely, gradual decrease of the number of
moving dislocations.
In [19] the FrankRead mechanism of dislocation
multiplication was considered to explain the results of
action of microwave radiation on GaAs. Special attention
was paid to analysis of variation of the critical field
strength Ec leading to generation of dislocation loops. The
calculations made in [19] showed that production of
critical electric field (Ec = 1.7×107 V/m) in GaAs requires
application of microwave frequencies of about 84 GHz.
At the same time, the authors of [19] considered a
possibility of Ec reduction as the frequency of microwave
oscillations is approaching the eigenfrequencies of
dislocation vibrations. For GaAs, the minimal
eigenfrequency of vibrations of a dislocation segment of
length L = 103b (b is the Burgers vector) calculated
within the string model was 1 = 13 GHz. However, it
was noted in [19] that the impurity atoms accumulated at
dislocations may lead to decrease of the eigenfrequencies
of dislocation vibrations.
Let us consider resonance interaction of microwave
radiation with dislocations in somewhat different aspect.
Because of lattice mismatch of different layers, elastic
stresses appear in substrate and oxide layer of a
multilayer system (in our case, the composition of oxide
layers is close to stoichiometric one [4, 6]).
Compensation of lattice mismatch of the substrate and
oxide layer becomes energetically efficient not only due
to elastic strain over the whole interfacial area between
the two lattices but partially owing to dislocations
appearing at that surface as well [20]. In particular,
dislocations in silicon carbide are nuclei of stacking
faults (cubic SiC interlayers in 4Н-SiC or 6Н-SiC) in the
bulk of epitaxial layer or at the epitaxial layer–substrate
interface [21]. In this case, dislocations may split into
partials, thus leading to reduction of the energy of elastic
lattice distortions around dislocations.
It was noted in [22] that dislocation interaction with
a phonon leads to appearance of a stress field that may
cause movement of dislocation as a whole. Besides,
according to [17], interaction of dislocation with an
obstacle (the nature of the obstacle is not considered
here) results in appearance, along with characteristic
frequencies of the phonon spectrum (ph = 1061013 Hz),
of a set of natural vibrations of dislocations.
According to [23], an equation for displacement
u(y, t) of a dislocation loop (of length l) with rigid ends
and vibrating (similarly to an elastic string) under a
periodic external action may be presented as
.
2
2
b
y
u
uBuml
(2)
Here ml is the dislocation effective mass per unit
length, is the effective dislocation line tension, =
0e
it is the oscillating shear tension caused by an
external action, b is the Burgers vector modulus. The
boundary conditions are u(0, t) = u(l, t) = 0. A parameter
B in Eq. (2) corresponds to damping constant. The term
2
2
y
u
characterizes restoring force per unit length. The
value is estimated from the relation
,
2
1
~ 2Gb (3)
where G is the shear modulus. The quantity ml is
determined as
2bml , (4)
where is the material density.
According to [23], the dependence u(y, t) for a
dislocation loop is
,, 2
0
tieylyAtyu (5)
where A = /2. By inserting Eq. (5) in Eq. (2) and
integrating from y = 0 to y = l, we obtain
bAl
Al
Bi
Al
ml 2
66
33
2 , (6)
or
1
2
0
2
1
2
i
b
A , (7)
where
2
2
0
12
lml
(8)
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
230
and
12
2Bl
. (9)
At low attenuation, the quantity
2/00 (10)
acts as resonance frequency at which |A| achieves its
maximal value that is limited by the damping constant
only. By inserting Eqs. (3) and (4) in Eq. (8), we obtain
for the frequency 0:
222
2
2
0
62
1
12
l
G
lb
Gb
. (11)
Based on Eq. (10), it is possible to estimate size of
dislocations for which the frequency = 2.45 GHz of
microwave radiation used in our experiments is
resonance. In the case of = 0, we obtain
2
0
2
2
2
3
G
l . (12)
Inserting the values of and G for silicon carbide
(G = 160 GPa [14]) and SiO2, TiO2, Gd2O3 and Er2O3
oxide films in Eq. (12), we obtain that the frequency =
19 s1045.2 is resonance for partial dislocations of
length l cm10 4 .
Thus, resonance interaction of 2.45 GHz microwave
radiation with dislocations can result in release of
dislocations with l cm10 4 and their movement in
both silicon carbide substrate and oxide layer. The
movement of dislocations, in its turn, will lead to
variation of distribution of intrinsic stresses in the
structure under investigation, with further change of
number and configuration of dislocations.
When considering resonance interaction of
microwave radiation with dislocations one should take
into account that any impurities in a crystal that can serve
as obstacles for dislocations are sources of vibrations
with frequencies ph = 106-1013 Hz. Since the frequency
of microwave radiation used in the experiment lies in the
frequency range of obstacles vibrations, the condition of
resonance release of dislocation from an obstacle may be
fulfilled not only for dislocations of strictly determined
size but also for those of arbitrary size but attached to an
obstacle that is vibrating with the resonance frequency.
According to [20, 24], presence of dislocations in
material leads to local variations of both bandgap width
and concentration of impurities and lattice defects (in
particular, the stacking faults) near dislocations. In
silicon carbide, the stacking faults are interlayers of
cubic SiC in 4Н- or 6Н-SiC [21]. Owing to presence of
free or unsaturated bonds at dislocation nucleus as well
as to interaction of dislocations with impurities and
lattice defects, the corresponding energy levels appear in
the crystal bandgap. As a result, the band structure near
dislocations is extremely complicated [24].
Generally a dislocation forms isolated centers that
may serve as centers of radiative as well as non-radiative
electron-hole recombination [24]. It should be noted that
the energy released at non-radiative recombination of an
electron-hole pair in SiC is sufficient for overcoming a
barrier preventing atom displacement to another
position. I.e. a local reconstruction of hexagonal
polytype lattice to that of cubic one occurs, with
formation of a cubic polytype interlayer [21].
Anisotropy of dislocation movement [20, 24, 25]
enables one to explain the following experimental fact:
At similar microwave annealing conditions, structural
variations at the macroscopic level (in particular, those in
transmission spectra) were detected only if an oxide film
was deposited onto a crystalline substrate. No changes in
the transmission spectra of a structure were observed
after action of microwave radiation if an oxide film was
deposited onto a glass substrate. This result may be
explained as follows. Because of anisotropy of
dislocation movement [24, 25], a set of dislocations of
preferred orientation appears in a crystalline structure.
This results in anisotropic distribution of absorption
centers interacting with dislocations that shows itself in
the absorption spectra. There are no preferred
orientations in glass; therefore, average distribution of
defects and dislocations in a glass substrate remains
invariable at the macrolevel [26], even if variations in
dislocation distribution occur at the microlevel.
4. Conclusion
Thus, within the assumption of resonance interaction of
microwave radiation with dislocations that leads to
variation of dislocation number and configuration, one
can conclude that action of microwave radiation has to
result in redistribution of recombination centers at the
semiconductor–oxide layer interface. This, in its turn,
leads to appearance of additional bands in PL spectra of
the oxide film/SiC structures or intensity redistribution
for some bands in PL spectra of the SiO2/GaAs structure,
as well as to optical density variation for the oxide
film/SiC structures. It should be taken into account that,
because of anisotropy of dislocation movement in
crystals, the resonance interaction of microwave radiation
with dislocations is most efficient in structures with
crystalline substrates.
Acknowledgement
The author is indebted to Prof. A.M. Svetlichnyi for his
interest in this work and valuable discussions.
References
1. E.D. Atanassova, A.E. Belyaev, R.V. Konakova,
P.M. Lytvyn, V.V. Milenin, V.F. Mitin,
V.V. Shynkarenko, Effect of Active Actions on the
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
231
Properties of Semiconductor Materials and
Structures. NTC “Institute for Single Crystals”,
Kharkiv, 2007.
2. A.E. Belyaev, E.F. Venger, I.B. Ermolovich,
R.V. Konakova, P.M. Lytvyn, V.V. Milenin,
I.V. Prokopenko, G.S. Svechnikov, E.A. Soloviev,
L.I. Fedorenko, Effect of Microwave and Laser
Radiations on the Parameters of Semiconductor
Structures. Intas, Kyiv, 2002.
3. Yu.Yu. Bacherikov, R.V. Konakova,
E.Yu. Kolyadina, A.N. Kocherov, O.B. Okhrimenko,
A.M. Svetlichnyi, Effect of microwave radiation on
optical transmission spectra in SiO2/SiC structures //
Semiconductor Physics, Quantum Electronics &
Optoelectronics, 5(4), p. 391-394 (2002).
4. Yu.Yu. Bacherikov, R.V. Konakova, A.N. Kocherov,
P.M. Lytvyn, O.S. Lytvyn, O.B. Okhrimenko,
A.M. Svetlichnyi, Effect of microwave annealing on
silicon dioxide/silicon carbide structures // Technical
Phys., 48(5), p. 598-601 (2003).
5. O.B. Okhrimenko, Methods of improvement of
properties of the oxide layer–silicon carbide
interface // Ukr. J. Phys. Reviews, 6(1), p. 3-10
(2010).
6. Yu.Yu. Bacherikov, R.V. Konakova, V.V. Milenin,
O.B. Okhrimenko, A.M. Svetlichnyi,
V.V. Polyakov, Changes in characteristics of
gadolinium, titanium, and erbium oxide films on
the SiC surface under microwave treatment //
Semiconductors, 42(7), p. 868-872 (2008).
7. O.B. Okhrimenko, Effect of microwave irradiation
on radiating centers in the SiO2/GaAs structures //
Petersburg J. Electronics, 42(1), p. 27-30 (2005),
in Russian.
8. L.M. Kustov, I.M. Sinev, Microwave activation of
catalysts and catalytic processes // Russian J. Phys.
Chemistry A, 84(10), p. 1676-1694 (2010).
9. V.A. Bolotov, Yu.D. Chernousov, E.I. Udalov,
Yu.Yu. Tanashev, V.N. Parmon, The features of
performing high-temperature chemical reactions
under microwave field // Vestnik NGU. Ser. Fizika,
4(2), p. 78-83 (2009), in Russian.
10. J. Jacob, L.H.L. Chia, F.Y.C. Boey, Review.
Thermal and non-thermal interaction of microwave
radiation with materials // J. Materials Sci., 30,
p. 5321-5327 (1995).
11. K.I. Rybakov, A.G. Eremeev, S.V. Egorov,
Yu.V. Bykov, Z. Pajkic, M. Willert-Porada, Effect
of microwave heating on phase transformations in
nanostructured alumina // J. Phys. D: Appl. Phys.
41(10), 102008 (2008).
12. K.I. Rybakov, V.E. Semenov, Nonthermal action of
microwaves upon transport processes in ionics
(effects, mechanisms, and verification), in: Proc.
Intern. Symp. on Microwave, Plasma and
Thermochemical Processing of Advanced
Materials. Eds. S. Miyake, M. Samandi, p. 20-25,
JWRI, Osaka (1997).
13. Yu.K. Kovneristy, I.Yu. Lazareva, А.А. Ravayev,
Materials Absorbing Microwave Radiations.
Nauka, Moscow, 1982 (in Russian).
14. Electronic archive New Semiconductor Materials.
Characteristics and Properties
http://www.ioffe.ru/SVA/NSM/
15. D.V. Kulikov, Yu.V. Trushin, P.V. Rybin,
V.S. Kharlamov, Physical model for the evolution of
the defect system of silicon carbide with allowance
for the internal elastic stress fields during implantation
of Al+ and N+ and subsequent annealing // Technical
Phys., 44(10), p. 1168-1174 (1999).
16. Li Xiang-Biao, Shi Er-Wei, Chen Zhi-Zhan, Xiao
Bing, Optical characterization of 4H-, 6H- and
15R-SiC crystals // Chinese J. Struct. Chem.
26(10), p. 1196-1202 (2007).
17. Yu.I. Golovin, Magnetoplastic effects in solids //
Phys. Solid State, 46(5), p. 789-824 (2004).
18. R.B. Morgunov, Spin micromechanics in the
physics of plasticity // Physics-Uspekhi, 47(2),
p. 125-147 (2004).
19. I.B. Ermolovich, G.V. Milenin, V.V. Milenin,
R.V. Konakova, R.A. Red’ko, Modification of the
defect structure in binary semiconductors under the
action of microwave radiation // Technical Phys.,
52(9), p. 1173-1177 (2007).
20. A.G. Zaluzhnyi, Dislocations in Crystals, Their
Movement and Elastic Properties. MIFI, Moscow,
1990 (in Russian).
21. O.A. Ageev, A.E. Belyaev, N.S. Boltovets,
V.S. Kiselev, R.V. Konakova, A.A. Lebedev,
V.V. Milenin, O.B. Okhrimenko, V.V. Polyakov,
A.M. Svetlichnyi, D.I. Cherednichenko, Silicon
Carbide: Technology, Properties, Application.
“ISMA”, Kharkiv, 2010 (in Russian).
22. J.M. Ziman, Electrons and Phonons. Clarendon
Press, Oxford, 1960.
23. A.S. Nowick, B.S. Berry, An Elastic Relaxation in
Crystalline Solids. Academic Press, New York,
1972.
24. H.F. Matare, Defect Electronics in Semiconductors.
Wiley-Interscience, New York, 1971.
25. J.P. Hirth, J. Lothe, Theory of Dislocations.
McGraw-Hill, 1967.
26. E. Atanassova, R.V. Konakova, V.F. Mitin,
J. Koprinarova, O.S. Lytvyn, O.B. Okhrimenko,
V.V. Schinkarenko, D. Virovska, Effect of
microwave radiation on the properties of Ta2O5–Si
microstructures // Microelectronics Reliability, 45,
p. 123-135 (2005).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 3. P. 227-231.
PACS 78.70.Fy, 78.70.Gq
A model for non-thermal action of microwave radiation
on oxide film/semiconductor structures
O.B. Okhrimenko
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prospect Nauky, 03028 Kyiv, Ukraine
Phone: 38(044) 525-62-61; fax: 38(044) 525-83-42; e-mail: olga@isp.kiev.ua
Abstract. A model is considered that explains mechanism of non-thermal action of microwave radiation on the thin SiO2 (ТiO2, Er2O3, Gd2O3) film/SiC and SiO2/GaAs structures. It assumes that the centers of electron-hole recombination are redistributed because of resonance interaction between dislocations of certain length and microwave radiation. As a result, additional bands appear in photoluminescence (PL) spectra of the oxide film/SiC structures or intensities of some bands are redistributed in the PL spectra of the SiO2/GaAs structure, as well as optical density of the oxide film/SiC structures changes.
Keywords: microwave radiation, dislocation, transmission spectrum, photoluminescence, silicon carbide.
Manuscript received 03.03.14; revised version received 21.07.14; accepted for publication 16.09.14; published online 30.09.14.
1. Introduction
It is known that action of microwave radiation on device structures and final products (diodes, transistors, integrated circuits) often leads to their degradation and catastrophic failures. There are literature data indicating the effects of defect gettering and structural relaxation in semiconductor materials induced by microwave radiation. In those cases, attention is paid to non-thermal nature of such actions as well as on processes induced by them at the metal(semiconductor and insulator( semiconductor interfaces [1, 2] that are integral parts of MIS transistor structures. At the same time, there is no model in literature that could unambiguously explain mechanism of non-thermal action on the oxide layer/semiconductor structures.
In this work, a model is proposed that gives consistent explanation for mechanism of non-thermal action of microwave radiation on the thin oxide film SiO2 (ТiO2, Er2O3, Gd2O3)/SiC and SiO2/GaAs structures.
2. Experimental results
In experimental works [3-7] it was shown that a short-term microwave annealing of frequency 2.45 GHz leads to increase of optical transmission in thin oxide film/silicon carbide structures (Fig. 1) and appearance of additional bands in photoluminescence (PL) spectra of similar structures (Fig. 2) or redistribution of PL bands intensity, as in GaAs/SiO2 structures (Fig. 3).
It was shown in [1, 2, 8-12] that changes in semiconductor defect subsystem under action of microwave radiation may be of thermal as well as non-thermal character. The thermal mechanisms of action of microwave radiation may be classified into three groups for convenience [8, 9]. One of the possible mechanisms is related to dielectric polarization. Such type of action of microwave field on dielectric materials involves the following processes:
· distortion of electron clouds of separate atoms; generally the electron shells of many-electron atoms (those of high atomic number) are easier deformed (atoms are polarized easier);
· alignment of molecules or structural elements with a constant dipole momentum along the field lines;
· deformation (variation of bond angle and length) of molecules, both with and without dipole moment, under action of a microwave field.
Another mechanism of action of microwave radiation involves free-charge currents that are excited in solids and contribute to heating because of ohmic losses. This mechanism is typical for high-conduction solids. One more mechanism to be accounted for is due to ohmic losses related to eddy currents excited by magnetic fields.
400
500
600
700
800
0
2
4
6
8
10
12
14
a
Transmission, %
Wavelength, nm
1
2
3
4
5
400
500
600
700
800
0
2
4
6
8
10
12
14
16
Wavelength, nm
b
Transmission, %
1
2
3
4
5
400
500
600
700
800
2
4
6
8
10
12
14
c
Transmission, %
Wavelength, nm
1
2
3
4
5
Fig. 1. Transmission spectra of the oxide film/SiC structures: (a) TiO2, (b) Gd2O3, (c) Er2O3 taken before (1 – initial structure) and after microwave annealing. Total time of microwave annealing: 1 s (2), 2 (3), 3 (4), 8 (5) [6].
To determine the degree of thermal action of microwave radiation on the specimens under investigation, let us estimate temperature variation (T owing to such action. Since the oxide layer does not absorb microwave radiation [13], the only source of specimen heating is absorption of microwave radiation in semiconductor. Let us assume that the specimen absorbs the total microwave radiation, and the absorbed energy is uniformly distributed over the specimen volume. Then the highest possible temperature of heated specimen is
r
=
D
V
С
E
T
.
(1)
Here V is the specimen volume (in our case. the average specimen volume V = 0.0125 cm3); E = W(t is the energy passing to the specimen in a time t, W = P(V, P is the microwave radiation power per specimen unit volume (0.04 W/cm3); С(() is SiC thermal capacity (density): С = 620(750 J/kg(deg = 0.62(0.75 J/g(deg [14], ( = 3170 kg/m3 = 3.170 g/cm3 [14].
After inserting the above parameters to Eq. (1), taking irradiation time to equal 1 s and assuming that the total microwave radiation is absorbed by the specimen, we obtain that its temperature may change by (T = 0.02 . Therefore, it is possible to neglect the contribution from thermal mechanism when explaining the observed variations of properties of metal oxide film and silicon carbide at the film/SiC interface appearing under microwave irradiation.
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
PL intensity, arb.un.
Photon energy E, eV
1
2
3
4
Fig. 2. PL spectra of the oxide film/SiC structures taken before (1 – initial structure) and after microwave annealing (2 – TiO2/SiC, 3 – Gd2O3/SiC, 4 – Er2O3/SiC). Total time of microwave annealing 8 s [6].
0.6
0.8
1.0
1.2
1.4
1.6
0
1
2
3
4
5
6
Photon energy E, eV
PL
intensity
, arb.un.
1
2
3
4
5
6
Fig. 3. PL spectra of the SiO2/GaAs structure taken on the side of SiO2 film before (1 – initial structure) and after microwave annealing (2(6). Total time of microwave irradiation: 1 min (2), 2 (3), 3 (4), 8 (5), 13 (6) [7].
3. Possible model for non-thermal action of microwave radiation
A single quantum of microwave radiation of frequency 2.45 GHz is ~
eV
10
5
-
. This is much below the activation energy of migration for migration of inherent atoms, their vacancies and impurity atoms in SiC (from 1.47 eV [4] to 8 eV [15]) as well as phonon energy in silicon carbide (~
(
)
eV
10
100
10
3
-
×
-
[16]).
The most likely reason for appearance of non-thermal effect of microwave radiation is presence in a crystal of nonequilibrium states that cause sensitivity of defect structure to action of microwave radiation. In particular, it was noted in [17, 18] when considering effect of low electric fields on nonmagnetic crystals that such effect is just due to presence of structural defects in them. It may be assumed that microwave field (as magnetic field) can lower the potential barriers (related to random distribution of the fields of intrinsic stresses in a crystal) that must be surmounted to provide dislocation movement [17, 18].
Besides, microwave radiation can affect not only on the process of dislocation interaction with an obstacle but on the structure of dislocation nuclei and obstacles as well. The obstacles may be several impurity atoms and cation vacancies as well as be of variable composition [17, 18]. Relaxation of intrinsic stresses leads to inverse effect, namely, gradual decrease of the number of moving dislocations.
In [19] the Frank(Read mechanism of dislocation multiplication was considered to explain the results of action of microwave radiation on GaAs. Special attention was paid to analysis of variation of the critical field strength Ec leading to generation of dislocation loops. The calculations made in [19] showed that production of critical electric field (Ec = 1.7×107 V/m) in GaAs requires application of microwave frequencies of about 84 GHz. At the same time, the authors of [19] considered a possibility of Ec reduction as the frequency of microwave oscillations is approaching the eigenfrequencies of dislocation vibrations. For GaAs, the minimal eigenfrequency of vibrations of a dislocation segment of length L = 103b (b is the Burgers vector) calculated within the string model was (1 = 13 GHz. However, it was noted in [19] that the impurity atoms accumulated at dislocations may lead to decrease of the eigenfrequencies of dislocation vibrations.
Let us consider resonance interaction of microwave radiation with dislocations in somewhat different aspect. Because of lattice mismatch of different layers, elastic stresses appear in substrate and oxide layer of a multilayer system (in our case, the composition of oxide layers is close to stoichiometric one [4, 6]). Compensation of lattice mismatch of the substrate and oxide layer becomes energetically efficient not only due to elastic strain over the whole interfacial area between the two lattices but partially owing to dislocations appearing at that surface as well [20]. In particular, dislocations in silicon carbide are nuclei of stacking faults (cubic SiC interlayers in 4Н-SiC or 6Н-SiC) in the bulk of epitaxial layer or at the epitaxial layer–substrate interface [21]. In this case, dislocations may split into partials, thus leading to reduction of the energy of elastic lattice distortions around dislocations.
It was noted in [22] that dislocation interaction with a phonon leads to appearance of a stress field that may cause movement of dislocation as a whole. Besides, according to [17], interaction of dislocation with an obstacle (the nature of the obstacle is not considered here) results in appearance, along with characteristic frequencies of the phonon spectrum ((ph = 106(1013 Hz), of a set of natural vibrations of dislocations.
According to [23], an equation for displacement u(y, t) of a dislocation loop (of length l) with rigid ends and vibrating (similarly to an elastic string) under a periodic external action may be presented as
.
2
2
b
y
u
u
B
u
m
l
s
=
¶
¶
g
-
+
&
&
&
(2)
Here ml is the dislocation effective mass per unit length, ( is the effective dislocation line tension, ( = (0ei(t is the oscillating shear tension caused by an external action, b is the Burgers vector modulus. The boundary conditions are u(0, t) = u(l, t) = 0. A parameter B in Eq. (2) corresponds to damping constant. The term
2
2
y
u
¶
¶
g
characterizes restoring force per unit length. The ( value is estimated from the relation
,
2
1
~
2
Gb
g
(3)
where G is the shear modulus. The quantity ml is determined as
2
b
m
l
r
»
,
(4)
where ( is the material density.
According to [23], the dependence u(y, t) for a dislocation loop is
(
)
(
)
,
,
2
0
t
i
e
y
ly
A
t
y
u
w
-
s
=
(5)
where A = (/2(. By inserting Eq. (5) in Eq. (2) and integrating from y = 0 to y = l, we obtain
b
Al
Al
B
i
Al
m
l
=
g
+
w
+
w
-
2
6
6
3
3
2
,
(6)
or
1
2
0
2
1
2
-
ú
û
ù
ê
ë
é
w
w
-
wt
+
g
=
i
b
A
,
(7)
where
2
2
0
12
l
m
l
g
=
w
(8)
and
g
=
t
12
2
Bl
.
(9)
At low attenuation, the quantity
p
w
=
n
2
/
0
0
(10)
acts as resonance frequency at which |A| achieves its maximal value that is limited by the damping constant only. By inserting Eqs. (3) and (4) in Eq. (8), we obtain for the frequency (0:
2
2
2
2
2
0
6
2
1
12
l
G
l
b
Gb
r
=
r
×
=
w
.
(11)
Based on Eq. (10), it is possible to estimate size of dislocations for which the frequency ( = 2.45 GHz of microwave radiation used in our experiments is resonance. In the case of ( = (0, we obtain
2
0
2
2
2
3
rn
p
=
G
l
.
(12)
Inserting the values of ( and G for silicon carbide (G = 160 GPa [14]) and SiO2, TiO2, Gd2O3 and Er2O3 oxide films in Eq. (12), we obtain that the frequency ( =
1
9
s
10
45
.
2
-
×
is resonance for partial dislocations of length l (
cm
10
4
-
.
Thus, resonance interaction of 2.45 GHz microwave radiation with dislocations can result in release of dislocations with l (
cm
10
4
-
and their movement in both silicon carbide substrate and oxide layer. The movement of dislocations, in its turn, will lead to variation of distribution of intrinsic stresses in the structure under investigation, with further change of number and configuration of dislocations.
When considering resonance interaction of microwave radiation with dislocations one should take into account that any impurities in a crystal that can serve as obstacles for dislocations are sources of vibrations with frequencies (ph = 106-1013 Hz. Since the frequency of microwave radiation used in the experiment lies in the frequency range of obstacles vibrations, the condition of resonance release of dislocation from an obstacle may be fulfilled not only for dislocations of strictly determined size but also for those of arbitrary size but attached to an obstacle that is vibrating with the resonance frequency.
According to [20, 24], presence of dislocations in material leads to local variations of both bandgap width and concentration of impurities and lattice defects (in particular, the stacking faults) near dislocations. In silicon carbide, the stacking faults are interlayers of cubic SiC in 4Н- or 6Н-SiC [21]. Owing to presence of free or unsaturated bonds at dislocation nucleus as well as to interaction of dislocations with impurities and lattice defects, the corresponding energy levels appear in the crystal bandgap. As a result, the band structure near dislocations is extremely complicated [24].
Generally a dislocation forms isolated centers that may serve as centers of radiative as well as non-radiative electron-hole recombination [24]. It should be noted that the energy released at non-radiative recombination of an electron-hole pair in SiC is sufficient for overcoming a barrier preventing atom displacement to another position. I.e. a local reconstruction of hexagonal polytype lattice to that of cubic one occurs, with formation of a cubic polytype interlayer [21].
Anisotropy of dislocation movement [20, 24, 25] enables one to explain the following experimental fact: At similar microwave annealing conditions, structural variations at the macroscopic level (in particular, those in transmission spectra) were detected only if an oxide film was deposited onto a crystalline substrate. No changes in the transmission spectra of a structure were observed after action of microwave radiation if an oxide film was deposited onto a glass substrate. This result may be explained as follows. Because of anisotropy of dislocation movement [24, 25], a set of dislocations of preferred orientation appears in a crystalline structure. This results in anisotropic distribution of absorption centers interacting with dislocations that shows itself in the absorption spectra. There are no preferred orientations in glass; therefore, average distribution of defects and dislocations in a glass substrate remains invariable at the macrolevel [26], even if variations in dislocation distribution occur at the microlevel.
4. Conclusion
Thus, within the assumption of resonance interaction of microwave radiation with dislocations that leads to variation of dislocation number and configuration, one can conclude that action of microwave radiation has to result in redistribution of recombination centers at the semiconductor–oxide layer interface. This, in its turn, leads to appearance of additional bands in PL spectra of the oxide film/SiC structures or intensity redistribution for some bands in PL spectra of the SiO2/GaAs structure, as well as to optical density variation for the oxide film/SiC structures. It should be taken into account that, because of anisotropy of dislocation movement in crystals, the resonance interaction of microwave radiation with dislocations is most efficient in structures with crystalline substrates.
Acknowledgement
The author is indebted to Prof. A.M. Svetlichnyi for his interest in this work and valuable discussions.
References
1. E.D. Atanassova, A.E. Belyaev, R.V. Konakova, P.M. Lytvyn, V.V. Milenin, V.F. Mitin, V.V. Shynkarenko, Effect of Active Actions on the Properties of Semiconductor Materials and Structures. NTC “Institute for Single Crystals”, Kharkiv, 2007.
2. A.E. Belyaev, E.F. Venger, I.B. Ermolovich, R.V. Konakova, P.M. Lytvyn, V.V. Milenin, I.V. Prokopenko, G.S. Svechnikov, E.A. Soloviev, L.I. Fedorenko, Effect of Microwave and Laser Radiations on the Parameters of Semiconductor Structures. Intas, Kyiv, 2002.
3. Yu.Yu. Bacherikov, R.V. Konakova, E.Yu. Kolyadina, A.N. Kocherov, O.B. Okhrimenko, A.M. Svetlichnyi, Effect of microwave radiation on optical transmission spectra in SiO2/SiC structures // Semiconductor Physics, Quantum Electronics & Optoelectronics, 5(4), p. 391-394 (2002).
4. Yu.Yu. Bacherikov, R.V. Konakova, A.N. Kocherov, P.M. Lytvyn, O.S. Lytvyn, O.B. Okhrimenko, A.M. Svetlichnyi, Effect of microwave annealing on silicon dioxide/silicon carbide structures // Technical Phys., 48(5), p. 598-601 (2003).
5. O.B. Okhrimenko, Methods of improvement of properties of the oxide layer–silicon carbide interface // Ukr. J. Phys. Reviews, 6(1), p. 3-10 (2010).
6. Yu.Yu. Bacherikov, R.V. Konakova, V.V. Milenin, O.B. Okhrimenko, A.M. Svetlichnyi, V.V. Polyakov, Changes in characteristics of gadolinium, titanium, and erbium oxide films on the SiC surface under microwave treatment // Semiconductors, 42(7), p. 868-872 (2008).
7. O.B. Okhrimenko, Effect of microwave irradiation on radiating centers in the SiO2/GaAs structures // Petersburg J. Electronics, 42(1), p. 27-30 (2005), in Russian.
8. L.M. Kustov, I.M. Sinev, Microwave activation of catalysts and catalytic processes // Russian J. Phys. Chemistry A, 84(10), p. 1676-1694 (2010).
9. V.A. Bolotov, Yu.D. Chernousov, E.I. Udalov, Yu.Yu. Tanashev, V.N. Parmon, The features of performing high-temperature chemical reactions under microwave field // Vestnik NGU. Ser. Fizika, 4(2), p. 78-83 (2009), in Russian.
10. J. Jacob, L.H.L. Chia, F.Y.C. Boey, Review. Thermal and non-thermal interaction of microwave radiation with materials // J. Materials Sci., 30, p. 5321-5327 (1995).
11. K.I. Rybakov, A.G. Eremeev, S.V. Egorov, Yu.V. Bykov, Z. Pajkic, M. Willert-Porada, Effect of microwave heating on phase transformations in nanostructured alumina // J. Phys. D: Appl. Phys. 41(10), 102008 (2008).
12. K.I. Rybakov, V.E. Semenov, Nonthermal action of microwaves upon transport processes in ionics (effects, mechanisms, and verification), in: Proc.
Intern. Symp. on Microwave, Plasma and Thermochemical Processing of Advanced Materials. Eds. S. Miyake, M. Samandi, p. 20-25, JWRI, Osaka (1997).
13. Yu.K. Kovneristy, I.Yu. Lazareva, А.А. Ravayev, Materials Absorbing Microwave Radiations. Nauka, Moscow, 1982 (in Russian).
14. Electronic archive New Semiconductor Materials. Characteristics and Properties http://www.ioffe.ru/SVA/NSM/
15. D.V. Kulikov, Yu.V. Trushin, P.V. Rybin, V.S. Kharlamov, Physical model for the evolution of the defect system of silicon carbide with allowance for the internal elastic stress fields during implantation of Al+ and N+ and subsequent annealing // Technical Phys., 44(10), p. 1168-1174 (1999).
16. Li Xiang-Biao, Shi Er-Wei, Chen Zhi-Zhan, Xiao Bing, Optical characterization of 4H-, 6H- and 15R-SiC crystals // Chinese J. Struct. Chem. 26(10), p. 1196-1202 (2007).
17. Yu.I. Golovin, Magnetoplastic effects in solids // Phys. Solid State, 46(5), p. 789-824 (2004).
18. R.B. Morgunov, Spin micromechanics in the physics of plasticity // Physics-Uspekhi, 47(2), p. 125-147 (2004).
19. I.B. Ermolovich, G.V. Milenin, V.V. Milenin, R.V. Konakova, R.A. Red’ko, Modification of the defect structure in binary semiconductors under the action of microwave radiation // Technical Phys., 52(9), p. 1173-1177 (2007).
20. A.G. Zaluzhnyi, Dislocations in Crystals, Their Movement and Elastic Properties. MIFI, Moscow, 1990 (in Russian).
21. O.A. Ageev, A.E. Belyaev, N.S. Boltovets, V.S. Kiselev, R.V. Konakova, A.A. Lebedev, V.V. Milenin, O.B. Okhrimenko, V.V. Polyakov, A.M. Svetlichnyi, D.I. Cherednichenko, Silicon Carbide: Technology, Properties, Application. “ISMA”, Kharkiv, 2010 (in Russian).
22. J.M. Ziman, Electrons and Phonons. Clarendon Press, Oxford, 1960.
23. A.S. Nowick, B.S. Berry, An Elastic Relaxation in Crystalline Solids. Academic Press, New York, 1972.
24. H.F. Matare, Defect Electronics in Semiconductors. Wiley-Interscience, New York, 1971.
25. J.P. Hirth, J. Lothe, Theory of Dislocations. McGraw-Hill, 1967.
26. E. Atanassova, R.V. Konakova, V.F. Mitin, J. Koprinarova, O.S. Lytvyn, O.B. Okhrimenko, V.V. Schinkarenko, D. Virovska, Effect of microwave radiation on the properties of Ta2O5–Si microstructures // Microelectronics Reliability, 45, p. 123-135 (2005).
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
227
_1465726299.unknown
_1465726567.unknown
_1465727682.bin
_1473589225.unknown
_1465726971.unknown
_1465727004.unknown
_1465726916.unknown
_1465726458.unknown
_1465726545.unknown
_1465726383.unknown
_1465384859.unknown
_1465384898.unknown
_1465385391.unknown
_1465385395.unknown
_1465384910.unknown
_1465384922.unknown
_1465384889.unknown
_1465384893.unknown
_1465384878.unknown
_1465038834.bin
_1465038932.bin
_1465038800.bin
_1464792281.bin
|
| id | nasplib_isofts_kiev_ua-123456789-118513 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2025-12-01T19:42:06Z |
| publishDate | 2014 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Okhrimenko, O.B. 2017-05-30T14:27:20Z 2017-05-30T14:27:20Z 2014 A model for non-thermal action of microwave radiation on oxide film/semiconductor structures / O.B. Okhrimenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 3. — С. 227-231. — Бібліогр.: 26 назв. — англ. 1560-8034 PACS 78.70.Fy, 78.70.Gq https://nasplib.isofts.kiev.ua/handle/123456789/118513 A model is considered that explains mechanism of non-thermal action of microwave radiation on the thin SiO₂ (ТiO₂, Er₂O₃, Gd₂O₃) film/SiC and SiO₂/GaAs structures. It assumes that the centers of electron-hole recombination are redistributed because of resonance interaction between dislocations of certain length and microwave radiation. As a result, additional bands appear in photoluminescence (PL) spectra of the oxide film/SiC structures or intensities of some bands are redistributed in the PL spectra of the SiO₂/GaAs structure, as well as optical density of the oxide film/SiC structures changes. The author is indebted to Prof. A.M. Svetlichnyi for his interest in this work and valuable discussions en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics A model for non-thermal action of microwave radiation on oxide film/semiconductor structures Article published earlier |
| spellingShingle | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures Okhrimenko, O.B. |
| title | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| title_full | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| title_fullStr | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| title_full_unstemmed | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| title_short | A model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| title_sort | model for non-thermal action of microwave radiation on oxide film/semiconductor structures |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/118513 |
| work_keys_str_mv | AT okhrimenkoob amodelfornonthermalactionofmicrowaveradiationonoxidefilmsemiconductorstructures AT okhrimenkoob modelfornonthermalactionofmicrowaveradiationonoxidefilmsemiconductorstructures |