Deposition of Al2O3 and SiO2 films via pyrolysis of aluminum acetylacetonate and hexamethyldisiloxane in the presence of nitrogen compounds

Article abstract of DOI:10.1023/A:1026685715881

Kinetic measurements were used to assess the effects of N₂O, NO, and diethylamine on the chemical vapor deposition of SiO₂ films on Si from hexamethyldisiloxane and the effect of diethylamine on the deposition of Al₂O

Full text of DOI:10.1023/A:1026685715881

Inorganic Materials, Vol. 36, No. 12, 2000, pp. 1243–1250. Translated from Neorganicheskie Materialy, Vol. 36, No. 12, 2000, pp. 1476–1484.
Original Russian Text Copyright © 2000 by Mittov, Ponomareva, Mittova, Novikova, Gadebskaya, Bezryadin.
Deposition of Al2O3 and SiO2 Films via Pyrolysis
of Aluminum Acetylacetonate and Hexamethyldisiloxane
in the Presence of Nitrogen Compounds
†
O. N. Mittov , N. I. Ponomareva, I. Ya. Mittova, E. D. Novikova,
T. A. Gadebskaya, and M. N. Bezryadin
Voronezh State University, Universitetskaya pl. 1, Voronezh, 394693 Russia
Received April 16, 1999; in final form, October 5, 1999
Abstract—Kinetic measurements were used to assess the effects of N2O, NO, and diethylamine on the chem-
ical vapor deposition of SiO2 films on Si from hexamethyldisiloxane and the effect of diethylamine on the dep-
osition of Al2O3 films on Si, GaAs, and InP from aluminum acetylacetonate. The composition of the films was
determined by electron probe x-ray microanalysis andAuger electron spectroscopy. The deposition kinetics and
properties of the films are correlated with the nature of the gaseous admixture and process parameters.
INTRODUCTION
The purpose of this work was to investigate the
CVD of oxide films on Si substrates via HMDSO
pyrolysis in the presence of N2O, NO, or diethylamine
and also on Si, GaAs, and InP substrates via pyrolysis
of aluminum acetylacetonate in the presence of diethy-
lamine.
The preparation of high-quality oxynitride films on
silicon is of practical importance in semiconductor
technology. The major approaches to producing oxyni-
tride films are chemical vapor deposition (CVD) at low
or atmospheric pressure and thermal nitridation of sil-
ica. The former approach involves pyrolysis of gas mix-
tures typically containing SiH4 (or SiH2Cl2), NH3, and
N2O (or NO) [1, 2]. The latter consists in heat treatment
of silicon or silica in NH3, NO, N2O, or N2 vapor [3, 4].
The use of nitrogen oxides for thermal oxidation of sil-
icon gives rise to changes in the deposition mechanism,
composition, and structure of the films and improves
their dielectric properties.
EXPERIMENTAL
In our preparations, we used commercial N2O; NO
was prepared as described in [8]. KDB (B-doped)
Si(100) wafers (ρ = 7.5 Ω cm) were cleaned by stan-
dard peroxide–ammonia cycles [9]. HMDSO (reagent
grade) was additionally purified by sublimation. CVD
was carried out in a resistance-heated horizontal quartz
reactor. The temperature was controlled with an accu-
racy of ±2°C. HMDSO was transported to the substrate
by an argon carrier flow at 25°C through a bubbler. The
argon flow rate was adjusted so that the HMDSO con-
centration in the gas phase was constant. The gas phase
contained, along with HMDSO and argon, N2O (GP 1),
air + N2O (GP 2), NO (GP 3), air + NO (GP 4), diethy-
lamine (GP 5), or air (GP 6). Al2O3 films were depos-
ited using aluminum acetylacetonate synthesized and
purified as described in [5]. Diethylamine was used
without dilution or was mixed with water (4.1 mol/l).
To assess the effect of diethylamine on the deposition
rate, composition, and properties of Al2O3 films, we
used two approaches, either introducing diethylamine
vapor into the gas phase during the pyrolysis of alumi-
num acetylacetonate or annealing as-deposited films in
diethylamine vapor. Deposition was carried out at
400°C in a resistance-heated furnace. The temperature
was maintained with a stability of ±2°C. Aluminum
acetylacetonate was contained in a cylinder at 250°C.
The flow rate of argon carrier gas was 3 l/h. The tem-
The effect of amines on the growth rate and proper-
ties of SiO2 and Al2O3 films being deposited from alu-
minum acetylacetonate and hexamethyldisiloxane
(HMDSO) [5, 6] is of great interest. First, because
amines are carrier killers: upon decomposition, they
recombine with the radicals resulting from the destruc-
tion of organoelement compounds, thereby suppressing
further decomposition of the radicals, which might oth-
erwise result in contamination of the growing film with
carbon [7]. Second, diethylamine is a nitrogen source,
and its reaction with aluminum acetylacetonate or
HMDSO may lead to the incorporation of nitrogen into
the film and formation of an oxynitride layer.
In developing new approaches to producing oxyni-
tride layers with controlled properties, it is expedient to
extend the range of suitable Si compounds and also to
assess the effects of nitrogen-containing gaseous
admixtures on the growth, composition, and properties
of the films.
†
Deceased.
0020-1685/00/3612-1243$25.00 © 2000 MAIK “Nauka/Interperiodica”

1244
d, nm
MITTOV et al.
1.8 times faster in the presence of diethylamine. The
index of refraction, n, of the films produced in the pres-
ence of diethylamine was somewhat higher than that of
the films grown in oxygen and argon without diethy-
lamine and varied, depending on the deposition dura-
tion, in the ranges 1.58–1.66, 1.64–1.66, and 1.57–1.64
for the Si, InP, and GaAs substrates, respectively. The
index of refraction of the films deposited on Si, InP, and
GaAs without diethylamine was 1.57–1.59, 1.61–1.64,
and 1.54–1.55, respectively.
350
300
250
200
150
100
50
6
4
3
1
The thicknesses and indices of refraction of the
Al2O3 films annealed in the presence of diethylamine at
400°C for 10 min are listed in Table 1.
5
2
0
To examine the possibility of enhancing the nitro-
gen content of Al2O3 films on Si, the films were
annealed between 400 and 600°C for 1 h in the pres-
ence of diethylamine vapor. The results are summa-
rized in Table 2. The compositions of the films depos-
ited via pyrolysis of aluminum acetylacetonate in the
presence of diethylamine and without it are listed in
Table 3. The average Al : O atomic ratio in the films
produced in oxygen + argon mixtures is 3 : 5, and that
in the films deposited in the presence of diethylamine is
3 : 2. As is well known, thermal decomposition of met-
alorganic (MO) compounds may occur both on the sub-
strate surface and in the gas phase [5]. Gas-phase reac-
tions are more likely near the decomposition tempera-
ture and at higher concentrations of the MO compound.
Besides, the probability of gas-phase decomposition is
higher for less stable and volatile compounds. It would
be expected that the introduction of admixtures into the
gas phase might also have a significant effect on the
dynamic equilibrium between the gas phase and the
growing film. Reactions between MO and nitrogen-
containing compounds can follow two, distinctly dif-
ferent paths: decomposition of the MO compound to
the metal, which then reacts with the admixture to form
a nitride, or radical substitution yielding an intermedi-
ate compound already containing bonds necessary for
film formation. Increasing the difference in redox
potential between the MO and nitrogen-containing
compounds favors heterolytic substitutions in MO
compounds [5]. It may be that, in the presence of dieth-
8
13
18
23
28
33
τ, min
Fig. 1. Film thickness as a function of deposition time for
Al O deposited on (1, 4) InP, (2, 5) Si, and (3, 6) GaAs sub-
2
3
strates via pyrolysis of aluminum acetylacetonate at 400°C
(4–6) in the presence of diethylamine (7.5 × 10 mol/h) and
(1–3) without it.
–2
perature of the diethylamine source was 70°C. Al2O3
was deposited on KDB Si(100) (ρ = 7.5 Ω cm),
SAGOCh GaAs(100) (carrier concentration, 1016 cm–3),
and FIE-1 InP(100) (2 × 1015 cm–3) substrates.
The film composition was determined by electron
probe x-ray microanalysis (EPXMA). Composition–
depth profiles were obtained by Auger electron spec-
troscopy (AES) with an IOS-10-005 instrument during
Ar+ ion milling. Film thicknesses were measured with
an LEF-3M ellipsometer to an accuracy of ±1 nm. The
IR spectra of the films were recorded with a UR-10 Carl
Zeiss spectrophotometer.
RESULTS AND DISCUSSION
The kinetics of Al2O3 deposition on Si, GaAs, and
InP substrates with and without diethylamine were
found to follow a linear rate law (Fig. 1). The deposi-
tion rate was independent of substrate material and was
Table 1. Thicknesses and indices of refraction of the Al2O3 Table 2. Effect of annealing temperature (diethylamine va-
films on Si before and after annealing in an argon + diethy- por, 1 h) on the thickness and index of refraction of Al2O3
lamine mixture at 400°C for 10 min
films on Si
d, nm
n
d, nm
before
n
tann, °C
before
annealing
before
annealing
after
before
after
after annealing
after annealing
annealing annealing annealing annealing
50
114
114*
200
50
107
110*
167
1.78
1.56
1.56*
1.58
1.66
1.55
1.55*
1.56
400
450
510
600
60
104
107
68
60
91
93
57
1.59
1.58
1.58
1.58
1.69
1.78
1.79
1.79
* Annealing without diethylamine.
INORGANIC MATERIALS Vol. 36 No. 12
2000

DEPOSITION OF Al2O3 AND SiO2 FILMS
1245
v, nm/min
4.5
n
1.8
d, nm
180
160
140
120
100
80
4.0
3.5
3.0
2.5
2.0
1.5
1.7
1.6
1.5
4
3
2
2
1
1
1.4
1.3
60
0
5
10
15
20
25
30
1.0
640
τ, min
680
720
760
800
t, °C
Fig. 3. (1, 2) Growth rate and (3, 4) index of refraction vs.
Fig. 2. Film thickness as a function of deposition time for
temperature for SiO deposited on Si via pyrolysis of
SiO deposited on Si via pyrolysis of HMDSO (1.4 mol/h)
2
2
–2
at 750°C (1) in the presence of diethylamine (7.5 ×
HMDSO (1.4 × 10 mol/h) (2, 3) in air and (1, 4) in the
−2
–2
10 mol/h) and (2) in air (31 l/h).
presence of diethylamine (0.4 × 10 mol/h).
ylamine, radical substitutions in aluminum acetylacet- layer and rapidly decreases with depth, whereas the
onate lead to the formation of an intermediate alumi-
num compound containing Al–N bonds. However, we
found no nitrogen in the films, which were enriched in
aluminum. This finding, together with the fact that the
deposition kinetics were independent of substrate
material, leads us to assume that the reaction rate is
controlled by a gas-phase process. Moreover, the films
deposited in the presence of diethylamine contained no
carbon, presumably because of the aforementioned
suppression of secondary radical decomposition, pre-
venting contamination with carbon.
carbon content of the film deposited at 800°C is high
throughout the film thickness. Free Si is missing in the
top layer, but its content rises deeper into the film,
passes through a flat maximum at half thickness, then
drops sharply, and rises again at the film–substrate
interface. The content of silicon bonded to oxygen rises
with depth in all of the films studied, and at the inter-
face all of the silicon is coordinated by oxygen.
The presence of free silicon seems to be due to the
redox process 2SiO
SiO2 + Si. Concurrently, the
oxygen incorporated into the film oxidizes silicon:
The kinetics of SiO2 growth on Si via pyrolysis of
HMDSO both in the presence of diethylamine and
without it followed a parabolic rate law (Fig. 2). The
introduction of diethylamine into the gas phase (GP 1)
reduced the growth rate of SiO2 on Si in comparison
with deposition in air (GP 2) (Fig. 3). The decrease in
growth rate with increasing temperature or on the addi-
tion of an admixture is likely to be associated with a
reduction in the time span between adsorption and
reaction events or a reduction in the effective density of
surface sites. The lower growth rate in the presence of
diethylamine can be accounted for under the assump-
tion that the reaction of HMDSO with diethylamine
occurs in the gas phase, as in the case of aluminum
acetylacetonate. The indices of refraction of the films
deposited from GP 1 were higher, presumably because
of the formation of oxynitride layers.
1
--
2
1
--
2
Si + xO2
SiOx. As evidenced by depth profiling
data, most of the silicon combines with oxygen to form
a nonstoichiometric oxide. The presence of nitrogen
testifies to radical substitution reactions yielding an
Table 3. Elemental composition (at. %) of Al2O3 films pro-
duced by aluminum acetylacetonate pyrolysis in air + argon
and argon + diethylamine mixtures (EPXMA data)
Substrate
Gas phase
Air + argon
d, nm Al
O
C
Si
505 34.8 62.1 3.1
831 37.6 60.1 2.2
759 37.5 60.4 2.1
303 63.3 36.7 –
297 60.7 39.3 –
322 56.5 43.5 –
GaAs
InP
Si
″
″
Argon + diethylamine
This assumption is supported by AES data (Fig. 4).
The films deposited at different temperatures all con-
tain nitrogen. In the films produced between 650 and
750°C, the carbon content is fairly high in the surface
GaAs
InP
″
″
INORGANIC MATERIALS Vol. 36
No. 12 2000

1246
100
MITTOV et al.
(a)
(b)
80
60
40
20
3
3
5
2
5
2
4
4
1
1
0
20
40
60
80
100
0
5
10
15
(d)
20
25
100
(c)
80
60
40
20
4
2
5
5
4
3
2
3
1
1
0
Ion-milling time
5
10
15
20
25
30
35
40
0
2
4
6
8
10 12 14 16 18 20
Fig. 4.AES depth profiles of films deposited on Si via HMDSO pyrolysis in the presence of diethylamine at (a) 650, (b) 700, (c) 750,
and (d) 800°C; deposition time, 10 min; (1) N, (2) C, (3) free Si, (4) combined Si, (5) O.
intermediate organosilicon compound containing Si–N in GP 2 and by a factor of 1.5–5 than in argon without
N2O.
bonds, which then converts into the final product. The
low nitrogen content of the films and the reduced
growth rate in the presence of diethylamine suggest that
the reaction between diethylamine and HMDSO occurs
in the gas phase. The resulting molecular fragments
decompose further on the substrate surface. Judging
from the sharp decrease in carbon content in the near-
surface region, this process is accompanied by breaking
of Si–C bonds in the molecular fragments and carbon
removal in the form of volatile compounds.
The growth rate as a function of N2O flow rate at a
constant HMDSO concentration (10–4 mol/l) shows a
maximum at 2–2.5 mol/h, independent of temperature
(Fig. 6). In the temperature range 500–650°C, the
growth rate is substantially slower than that in the range
700–850°C. At lower temperatures, the highest deposi-
tion rate (3–14 nm/min) was observed in GP 1 at
HMDSO : N2O molar ratios of 1 : 100 to 1 : 150. At
higher temperatures, the deposition rate attains 36–
60 nm/min at HMDSO : N2O from 1 : 150 to 1 : 200.
Figure 5 displays the temperature dependences of
the growth rate and index of refraction for films depos-
ited from HMDSO in argon atmosphere, GP 1, and
GP 2. Quantitative deposition of oxide films begins at
500°C in GP 1 and only at 650°C in GP 2 and argon.
The growth rate rises nearly exponentially in GP 1 and
is almost linear with temperature in GP 2 and argon.
The index of refraction of the films deposited in GP 2
increases with temperature, falling in the range 1.4–
1.62. The n of the films grown in GP 1 is lower (1.25 to
The Arrhenius plot of the deposition rate in GP 1
(Fig. 7) consists of two linear portions with a break at
750°C. The plots for CVD in GP 2 and argon are linear
over the entire temperature range studied. For the CVD
process in GP 1, the apparent activation energy Ea
derived from the data in Fig. 7 is 84 kJ/mol in the range
500–750°C and 25 kJ/mol between 750 and 850°C. The
Ea of CVD in GP 2 is 40 kJ/mol, and that of the process
in argon without N2O is 54 kJ/mol. Thus, the introduc-
1.5) and passes through a maximum around 550°C. The tion of N2O into the gas phase accelerates the deposi-
growth rate in GP 1 is higher by a factor of 4–10 than
tion rate and changes Ea. The Ea of CVD in the pres-
INORGANIC MATERIALS Vol. 36
No. 12 2000

DEPOSITION OF Al2O3 AND SiO2 FILMS
1247
ence of N2O is higher than that of the process without
v, nm/min
n
N2O by a factor of 1.6 in the temperature range 500–
750°C and is lower by a factor of 2 between 750 and
850°C. The Ea of 25–40 kJ/mol indicates that both pro-
cesses are diffusion-controlled [10]. The high Ea of the
CVD process in GP 1 between 500 and 750°C testifies
to an increase in the contribution of the reaction
between HMDSO and N2O or products of its decompo-
sition. In the range 750–850°C, the activation energy
decreases abruptly, presumably because of the increas-
ing effect of diffusion on the rate of the overall process.
Two interrelated processes take place on the surface of
the growing film: thermolysis and oxidation of the pre-
cursor. The variations in the activation energy and dep-
osition rate seem to be due to different surface reactions
between thermally activated HMDSO molecules and
50
1.7
1.6
1.5
1.4
1.3
1.2
1
3
40
30
20
4
6
atmospheric oxygen or the atomic oxygen resulting 10
from the decomposition of N2O or NO. As shown ear-
lier [3, 4], during thermal nitridation of Si in the pres-
ence of N2O between 950 and 1000°C, N2O dissociates
5
2
1.1
1.0
0
to form NO, oxygen, and nitrogen, and Si is oxidized
500
600
700
t, °C
800
900
by both NO and oxygen. The atomic oxygen appearing
as a reaction intermediate affects the nitrogen content
and distribution in the film. Clearly, in the CVD process
in the presence of N2O, taking place at lower tempera-
tures, the deposition rate between 750 and 850°C
depends on the effects of both NO and O2. To assess the
roles of NO and O2, we studied CVD from HMDSO in
the presence of NO (GP 3) and NO + air (GP 4) at
650°C. As in the preceding experiments, the HMDSO
concentration was maintained constant at 0.2 ×
10−3 mol/l by adjusting the flow rate of argon carrier
gas. The plots of deposition rate vs. NO flow rate
(Fig. 8) show a maximum at an HMDSO : NO molar
Fig. 5. (1, 2, 5) Deposition rate and (3, 4, 6) index of refrac-
tion vs. temperature for CVD from HMDSO in (1, 3) GP 1,
(2, 4) GP 2, and (5, 6) N O-free atmosphere; 1.4 ×
2
−2
10 mol/h HMDSO, 1.4 mol/h N O, 1.4 mol/h air;
2
–4
HMDSO concentration in the gas phase, 3 × 10 mol/l.
v, nm/min
60
ratio of 1 : 50 in GP 3 and 1 : 57 in GP 4. At these molar
ratios, the deposition rate in GP 4 (NO + O2) is almost
twice as high (11.5 nm/min) as that in GP 3 (NO) (11.5
and 6.5 nm/min, respectively). In terms of the total
amount of oxidants (NO + O2), the highest deposition
rate in GP 4 was observed at an HMDSO : NO + O2
molar ratio of 1 : 87. At this molar ratio, the deposition
rate in GP 3 (no oxygen) was 4–6 times slower. At
HMDSO : NO = 1 : 87 in GP 3, the deposition rate was
2.7 nm/min (Fig. 8). Thus, the presence of air + NO
mixtures (GP 4) or N2O (GP 1) ensures the highest dep-
osition rates: 11.5 and 13 nm/min, respectively, at
650°C.
50
8
40
7
6
30
5
2
4
1
3
2
1
The AES depth profiles of the films deposited from
HMDSO in different atmospheres are displayed in
Fig. 9. CVD in GP 2 yielded films with the same com-
bined Si : oxygen atomic ratio as in SiO2 (Fig. 9a). The
data for the films deposited in the presence of NO
(GP 3) indicate a high content of free silicon near the
film–substrate interface (Fig. 9b). The films deposited
in GP 3 contain nitrogen and high concentrations of
carbon as compared to GP 2. The observed combined
Si : oxygen ratio indicates the formation of the unstable
0
1
2
3
4
5
v
N O, mol/h
2
Fig. 6. Deposition rate as a function of N O flow rate at
(1) 500, (2) 550, (3) 600, (4) 650, (5) 700, (6) 750, (7) 800,
and (8) 850°C; 1.2 × 10 mol/h HMDSO, 2 l/h Ar; deposi-
tion time, 3 min.
2
–2
INORGANIC MATERIALS Vol. 36
No. 12 2000

1248
logv [nm/min]
MITTOV et al.
v, nm/min
14
4.2
3.7
3.2
2.7
2.2
1.7
1.2
12
10
8
2
3
6
2
1
1
4
2
0.7
0.2
0.8
0.9
1.0
1.1
1.2
1.3
1.4
0
0.2
0.4
0.6
0.8
1.0
1.2
103T, K–1
VNO, mol/h
Fig. 8. Deposition rate as a function of NO flow rate for
CVD in (1) GP 3 and (2) GP 4.
Fig. 7. Arrhenius plots of deposition rate for CVD in
(1) GP 2, (2) argon without N O, and (3) GP 1.
2
monoxide SiO. Pyrolysis of oxygen-containing orga- by the organic molecule. The films deposited in GP 1
nosilicon compounds yields SiO2, SiO, C, and organic
radicals. The amount of SiO depends on the amount of
and GP 4 were found to differ markedly in composition
from those deposited in GP2 and GP 3. As can be seen
reacting oxygen, which is supplied, for the most part, in Figs. 9c and 9d, the films deposited in GP 1 and GP 4
100
Free Si
(a)
(b)
80
60
40
20
Free Si
O
Combined Si
O
Combined Si
C
N
C
N
0
3
5
7
10
15
20
0
10
20
O
30
40
50
100
80
60
40
20
Free Si
(c)
(d)
Free Si
O
Combined Si
Combined Si
C
C
N
N
0
2
4
6
8
10 12 14 16
0
10
20
30
40
Ion-milling time
–2
Fig. 9. AES depth profiles of oxide films deposited from HMDSO (1.4 × 10 mol/h): (a) GP 1 (0.7 mol/h N O), 800°C; (b) GP 3
2
(0.7 mol/h NO), 650°C; (c) GP 2 (2.1 mol/h N O), 800°C; (d) GP 4 (0.7 mol/h NO), 650°C.
2
INORGANIC MATERIALS Vol. 36
No. 12 2000

DEPOSITION OF Al2O3 AND SiO2 FILMS
1249
Table 4. Electrical properties and growth rates of films de- strength to the films grown in GP 1 at HMDSO : N2O =
posited using HMDSO (1.4 mol/h) at different substrate tem-
1 : 150. The resistivity of the films deposited in the
peratures and N2O : HMDSO ratios (GP 1, 2.1 mol/h N2O)
presence of only NO (GP 3) was one order of magni-
tude lower than that of the films grown in GP 1.
Substrate
N2O : HMDSO
Electrical measurements on the Al2O3 and SiO2
films deposited from aluminum acetylacetonate and
HMDSO, respectively, in the presence of diethylamine
show that this admixture has little effect on film prop-
erties. The most marked changes were found in dielec-
tric permittivity, which was higher by a factor of 1.5–2
in the films grown in the presence of diethylamine in
comparison with those produced in air, which is attrib-
utable to the higher carbon content of the latter.
tempera-
v, nm/min ρ, Ω cm Ebr, V/cm
molar ratio
ture, °C
800
800
800
800
850
150
100
75
49
44
39
33
60
6 × 1013 4 × 106
7 × 108 3 × 105
4 × 108 2.5 × 105
6 × 108 3 × 105
4 × 1013 3 × 106
50
200
CONCLUSION
Our results on the CVD of SiO2 films on Si via
pyrolysis of HMDSO in the presence of N2O, NO, or
NO + air mixtures demonstrate that the deposition rate
and film composition depend on the gas-phase compo-
sition and HMDSO : oxidant molar ratio. The effects of
N2O (GP 1) and NO + air mixtures (GP 4) on the dep-
osition rate and film composition are somewhat similar,
in accordance with the fact that these atmospheres are
close in composition at high temperatures because of
the N2O decomposition into NO and oxygen. At low
temperatures, the CVD process is limited mainly by the
rate of surface reactions, which is in turn controlled by
the rate of chemisorption. At high temperatures, the
process is limited by the rate of reactant transport,
contain high levels of free Si distributed throughout the
film thickness. The presence of free Si is likely due to
the reaction 2SiO
SiO2 + Si, which is highly prob-
able in GP 1 and GP 4 at high deposition rates. The
absence and low content of free Si in the films grown in
GP 3 and GP 2, respectively, are obviously due to the
1
2
1
2
--
--
competing process Si + xO2 = SiOx. The films pre-
pared in the presence of NO or N2O contained nitrogen
at all depths. In the films grown in GP 4, carbon was
present only in the top layer and its content was sub-
stantially lower in comparison with the films deposited
in GP 1.
The IR spectra of the films deposited in the presence which is a weak function of temperature. The increase
of N2O or NO contain bands at 1090 and 460 cm–1 due
in deposition rate as the temperature is raised from
500–750 to 750–850°C and the decrease in the
HMDSO : N2O ratio ensuring the highest growth rate
suggest that the CVD process is limited by the thermol-
ysis of the metalorganic precursor. The same is evi-
denced by the AES depth profiling data.
The introduction of diethylamine into the gas phase
has a significant effect on the deposition kinetics,
increasing (in the case of aluminum acetylacetonate) or
reducing (in the case of HMDSO) the growth rate. This
effect depends strongly on whether the reaction takes
place on the substrates surface or in the gas phase. The
growth kinetics, composition, and properties of the
films depends on the extent of decomposition—to an
oxide or to an intermediate complex of diethylamine
(or products of its decomposition) with aluminum
acetylacetonate or HMDSO.
to Si–O bonds and a broad band at 830–860 cm–1
characteristic of the Si–N bonds in amorphous Si3N4
films [11].
The electrical properties of the films were found to
depend strongly on the gas-phase composition
(Table 4). The highest resistivity and dielectric strength
were found in the films grown in GP 1 at HMDSO :
N2O molar ratios of 1 : 150 (800°C) and 1 : 200
(850°C), corresponding to the highest deposition rate
and stoichiometric combined Si : oxygen ratio. At other
HMDSO : N2O ratios in GP 1, the breakdown strength
Ebr and resistivity ρ were lower. Note that the advanta-
geous dielectric properties of the films grown in GP 1
at 850°C and HMDSO : N2O = 1 : 200 may be due in
certain measure to the formation of a thin buffer oxide
layer [12]. The depth profile of the film deposited at
850°C demonstrates that only combined Si and oxygen
are present at the film–substrate interface. The absence
of carbon and nitrogen also suggests that a thin layer of
oxidized Si is present at the interface. Clearly, the for-
mation of this buffer layer accounts for the improved
electrical properties of the films deposited from GP 2
and GP 4, containing air along with N2O and NO. The
films deposited from GP 4 at HMDSO : NO : O2 =
1 : 57 : 30 were close in resistivity and dielectric
REFERENCES
1. Kuiper, A.E.T., Koo, S.W., and Habraken, F.H.P.M.,
Deposition and Composition of Silicon Oxynitride
Films, J. Vac. Sci. Technol., B, 1983, vol. 1, pp. 62–66.
2. Remerie, J. and Maes, H.E., Physical and Electrical
Characterization of LPCVD Oxynitride Layers, Proc.
Int. Conf. on Insulating Films on Semiconductors,
Amsterdam, 1986, pp. 15–19.
INORGANIC MATERIALS Vol. 36
No. 12 2000

1250
MITTOV et al.
3. Yorume, Y., Distribution of Nitrogen in Thermally
Nitrided SiO2, J. Vac. Sci. Technol., 1983, vol. 1,
pp. 67−71.
4. Menondez, J., Fernandez, M., and Sacedon, J.Z., Ther-
mal Nitridation of Silicon Dioxide Films, J. Vac. Sci.
Technol., B, 1988, vol. 6, no. 1, pp. 45–47.
5. Razuvaev, G.A., Gribov, B.N., Domrachev, G.A., and
Salamatin, B.A., Metalloorganicheskie soedineniya v
elektronike (Metalorganic Compounds in Electronics),
Moscow: Nauka, 1972.
6. Gribov, B.G., Domrachev, G.A., and Zhuk, B.V., Osazh-
denie plenok i pokrytii razlozheniem metalloorgani-
cheskikh soedinenii (Deposition of Films and Coatings
from Metalorganic Precursors), Moscow: Nauka, 1981.
kikh reaktivov i preparatov v laboratornykh usloviyakh
(Pure Chemical Substances: A Guide to the Preparation
of Chemical Reagents and Compounds under Labora-
tory Conditions), Moscow: Khimiya, 1974.
9. Ugai, Ya.A., Anokhin, V.Z., Mittova, I.Ya., et al., Ther-
mal Oxidation Kinetics of Silicon in the Presence of
Antimony and Bismuth Chlorides, Zh. Fiz. Khim., 1981,
vol. 55, no. 4, pp. 946–949.
10. Chu, T.Z., Szedon, J.R., and Zie, C.H., Films of Silicon
Nitride–Silicon Dioxide Mixtures, J. Electrochem. Soc.,
1968, vol. 115, no. 37, pp. 318–322.
11. Chistyakov, Yu.D. and Rainova, Yu.P., Fiziko-khimi-
cheskie osnovy tekhnologii mikroelektroniki (Physico-
chemical Foundations of Microelectronic Technology),
Moscow: Metallurgiya, 1979.
7. Turro, N.J., Molecular Photochemistry, New York: Ben-
jamin, 1965. Translated under the title Molekulyarnaya
fotokhimiya, Moscow: Mir, 1967.
12. Kolobov, N.A. and Samokhvalov, M.M., Diffuziya i
okislenie poluprovodnikov (Diffusion and Oxidation of
Semiconductors), Moscow: Metallurgiya, 1975.
8. Karyakin, Yu.V. and Angelov, I.I., Chistye khimicheskie
veshchestva. Rukovodstvo po prigotovleniyu khimiches-
INORGANIC MATERIALS Vol. 36
No. 12 2000