Real-time evaluation of aluminum borohydride trimethylamine for aluminum chemical vapor deposition

Article abstract of DOI:10.1149/1.3089355

The chemical species in gas phase and on the surface of aluminum borohydride trimethylamine (ABHTMA) for aluminum chemical vapor deposition as a function of the hot-wall temperature and the chamber pressure were studied using two kinds of Fourier transfor

Full text of DOI:10.1149/1.3089355

Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
H333
0013-4651/2009/156͑5͒/H333/7/$23.00 © The Electrochemical Society
Real-Time Evaluation of Aluminum Borohydride
Trimethylamine for Aluminum Chemical Vapor Deposition
Sang-Woo Kang,a Young-Jae Park,a Yong-Sung Kim,b Yong-Hyeon Shin,a
and Ju-Young Yuna,z
aVacuum Center, Division of Advanced Technology and bNano Characterization Center, Korea Research
Institute of Standards and Science, Deajeon, 305-340, South Korea
The chemical species in gas phase and on the surface of aluminum borohydride trimethylamine ͑ABHTMA͒ for aluminum
chemical vapor deposition as a function of the hot-wall temperature and the chamber pressure were studied using two kinds of
Fourier transform IR spectroscopes installed at the end of the chamber. The absorbance of Al–H, B–H, C–H, and C–N stretching
features of ligands in ABHTMA in the gas phase and on the surface was sensitive to the variation of analysis conditions. The area
ratio of integrated absorbance of Al–H and B–H stretching features located at the different position could estimate the dissociation
rate of the ABHTMA, which was abruptly changed in the range of 140–160°C. With these results, the temperature dependence of
the film composition and quality could be explained. Additionally, the stabilities of the chemical species were investigated using
density functional theory calculations. The ABHTMA was found to be the most stable molecule when trimethylamine was rich and
borane and alane were close in their concentrations. Borane-trimethylamine was also found to be produced in alane-poor condi-
tions as a by-product.
© 2009 The Electrochemical Society. ͓DOI: 10.1149/1.3089355͔ All rights reserved.
Manuscript submitted November 19, 2008; revised manuscript received January 16, 2009. Published March 13, 2009.
Aluminum ͑Al͒ has been widely used as interconnect material in
the fabrication of integrated circuit devices.1,2 Physical vapor depo-
sition ͑PVD͒ techniques are often used to deposit Al films. However,
successful Al interconnection becomes extremely difficult, because
the size of the vias is decreasing and the aspect ratio is increasing.
So, the chemical vapor position ͑CVD͒ of Al has attracted consid-
erable attention as an alternative PVD metallization process. The Al
CVD process must have a suitable metallorganic precursor; that is, a
new precursor has to be designed for deposition. A variety of met-
allorganic precursors for Al CVD have been developed over the past
two decades. Trimethylaluminum ͑TMA͒ and triisobutylaluminum
were among the early Al precursors and were abandoned due to
impurities like carbon incorporated to films, low deposition rate, and
low reflective index. Dimethylethylamine ͑DMEAA͒, methylpyrro-
lidine alane ͑MPA͒,3 and trimethylamine alane ͑TMAA͒ including
the amine-alane adduct have been found, and these are expected to
yield high-purity ͑carbon-free͒ films due to no direct Al–C bonds in
their molecular structures. However, DMEAA and MPA have low
stability, and TMAA is a solid precursor. Normally, the solid precur-
sor makes it difficult to control the vapor flow in terms of maintain-
ing a constant surface area in the source.
allorganic precursor is decomposed or reacted during the process,
the stretching vibrations of ligands such as CH3, N–͑CH3͒3 of a
metallorganic precursor can be changed. With the spectrum mea-
sured by an FT-IR spectroscope, the reaction mechanism can be
investigated. Using FT-IR spectroscopy, the real-time studies of the
gas-phase species and adsorbed species on the surface have been
reported for Cu deposition from hexafluoroacetylacetonate ͑hfac͒
7
Cu͑vinyltrimethylsilane͒,5,6 Cu͑bis-dipivaloylmethanato͒
and
2
Cu͑hfac͒2,8,9 Al deposition from the TMMA-NH3 system,10 AlGaAs
deposition from the TMA–trimethylgallium–AsH3 system,11 SiO2
deposition from the tetraethylorthosilicate–ozone system,12 and dia-
mond from a CH4–H2–O2 gas mixture.13 In situ real-time FT-IR
spectroscopy is a useful technique for monitoring the process and
diagnosing a mechanism. Until now, ABHTMA has not been evalu-
ated and reported with an FT-IR spectroscope.
In this work, we studied the behavior of ABHTMA at the gas
phase and on the surface as a function of the temperature and the
pressure of a hot-wall reactor with modified FT-IR spectroscopy
after dosing ABHTMA for CVD. We also performed density-
function-theory calculations to show the stable species and by-
products during the Al CVD process. ABHTMA was found to be a
stable precursor for the Al CVD in the trimethylamine-rich and the
near-stoichiometric condition of alane and borane. By the dissocia-
tion of ABHTMA and the recombination of the molecules dissoci-
ated, the borane-trimethylamine complex could be produced.
4
Aluminum borohydride trimethylamine ͑ABHTMA, 99.999%͒
was recently developed for Al CVD. The ABHTMA was synthe-
sized by the reaction among four kinds of molecules ͓LiAlH4,
AlCl3, N͑CH3͒3, and NaBH4͔, and the reaction equation is below
LiAlH4 + AlCl3 + 2N͑CH3͒3 + 2NaBH4 → 2BH3AlH3:N͑CH3͒3
Experimental
ABHTMA is a clear, colorless liquid at room temperature, has no
direct Al–C bond, and has a high vapor pressure ͑68 Pa at 30°C͒.
The vapor pressure was measured by the homemade apparatus in-
stalled with a pressure gauge calibrated by international pressure
standard system in Korea Research Institute of Standards and Sci-
ence.
In order to study a newly developed precursor for device manu-
facturing, investigating chemical species under various conditions is
important. Researchers in this field have been interested in the Fou-
rier transform IR ͑FT-IR͒ system because it can observe accurately
the concentration of chemical species in real time, is noninvasive to
the process chamber, and has low maintenance costs.
The FT-IR system was installed at the end of the hot-wall reactor
chamber to investigate the gas species coming out of the chamber
during Al deposition ͑Fig. 1͒ with varying deposition temperatures
and chamber pressures. The modified gas cell and the tube of the
FT-IR system was heated to 40°C in order to avoid contamination of
the gas cell, potassium bromide ͑KBr͒ windows, and pumping lines.
A collimated IR beam from the FT-IR spectrometer ͑Nicolet Avata
360͒ was passed through the gas cell with two KBr windows, and a
liquid-nitrogen-cooled Hg–Cd–Te detector was used. The IR band
under examination covered wavenumbers ranging from
400 to 4000 cm−1, and each IR spectrum was collected at 2 cm−1
resolution using 62 scans to allow a good signal-to-noise ratio. The
gas-cell pressure was controlled by the throttle valve. We used an-
other FT-IR system called a transmission FT-IR spectroscope to ob-
tain the information on the species adsorbed on the surface. This
system requires high-surface-area particles. The ZrO2 nanoparticles
were obtained from Nanomaterials Research Corporation ͑Long-
mont, CO͒ and were spherical with an average diameter of 50 nm.
More precursors have many bonds and vibrations which can be
conjugated, leading to IR absorptions at characteristic frequencies
that may be related to chemical groups ͑called ligands͒. If the met-
z E-mail: jyun@kriss.re.kr; swkang@kriss.re.kr
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H334
Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
Figure 1. ͑Color͒ Schematic of diagram
of diagnosis system.
ABHTMA. The assignment of the borane-trimethylamine complex
lines was confirmed by the IR spectrum library supported by the
Nicolet Avata software.
The ZrO2 nanoparticles were supported by a photoetched tungsten
grid. Before taking a spectrum of adsorbed species, the Al film was
deposited on the pressed ZrO2 nanoparticles for 10 min at 150°C
with ABHTMA because of changing ZrO2 surface to Al metal sur-
face. The transmission FT-IR spectroscope system has been reported
in previous studies.14-16 The ABHTMA was evaporated from a stain-
less steel bubbler maintained at an appropriate temperature of 25°C
and transported to the reactor by Ar carrier gas at a rate of 20 sccm.
The temperature of the feeding lines between the chamber and bub-
bler is 40°C, which is the same as the exhaust-line temperature.
We also performed density-functional theory calculations with
ultrasoft pseudopotentials,17 as implemented in the Vienna Ab Initio
Simulation Package code.18 A plane-wave cutoff of 400 eV and a
cubic supercell containing a molecule with a volume of 10 ϫ 10
ϫ 10 Å3 were used. The generalized gradient approximation for the
exchange-correlation energy was used.19
Figure 6 shows the change of the C–H, C–N, and Al–H stretch-
ing features at the reactor pressure of 0.95 Torr as a function of the
reactor wall temperature. The C–H stretching features located in the
range of 1420–1520 cm−1 ͑Fig. 6a͒ and 2850–3100 cm−1 ͑Fig. 6b͒
gradually decreased with the increase of the reactor wall tempera-
ture. However, the C–H stretching feature at 2964 cm−1 ͑CH2 asym-
metric stretch͒ increased with increasing the temperature over
175°C due to the decomposition of CH3 groups at a trimethylamine
ligand in ABHTMA. The C–H stretching vibration is normally
strong and the intensity is higher. Thus, the C–H stretching features
were used to investigate the decomposition of the precursor. For
example, the ␤-hydride elimination between neighboring methyl
Results and Discussion
First, we investigated the stabilities of molecules composed of
the alane, borane, and trimethylamine molecular components. The
molecular structures of ABHTMA are shown in Fig. 2. The calcu-
lated formation energies for various molecules are plotted in Fig. 3
as a function of the alane chemical potential ͓␮͑AlH3͔͒. The high
␮͑AlH3͒ represents the alane-rich condition in the chamber, while
the low ␮͑AlH3͒ is the borane-rich condition. When the trimethyl-
amine concentration is rich ͑Fig. 3͒ and the concentrations of alane
and borane are similar, the ABHTMA molecule is found to be the
most stable among those composed of the alane, borone, and tri-
methylamine molecules. Thus, in the rich condition of the trimethyl-
amine and the near-stoichiometric condition of the alane and borane,
the ABHTMA can be a stable precursor. As the concentration of the
alane component becomes reduced, the most stable species becomes
the borane-trimethylamine complex, as shown in Fig. 3. The
ABHTMA precursors used can also be degraded by the formation of
the borane-trimethylamine complex. The schematic diagram about
the chemical reaction in the gas phase and on the surface is shown in
Fig. 4 to facilitate understanding.
H
B
Al
N
Figure 5 shows the measured IR absorption spectrum for the
chemical species coming out of the reactor at 40°C wall tempera-
ture. The stretching features of Al–H ͑1844, 1793, and 1007 cm−1͒,
Al–N ͑746 cm−1͒, B–H ͑2485, 2443, and 2169 cm−1͒, C–N ͑2828
and 2775 cm−1͒, and C–H ͑2927, 2988, and 1484 cm−1͒ from
ABHTMA are clearly detected. Those peaks have been identified
from similar molecules elsewhere.20,21 In this spectrum, we found
the other B–H peaks ͑2394, 2382, and 2374 cm−1͒ related to the
borane-trimethylamine complex, which can be generated during the
dissociation and recombination of ABHTMA passing the hot-wall
reactor or contained little as the impurity of the synthesized
C
Figure 2. ͑Color͒ The calculated molecular structures of ͑a͒ borane-
trimethylamine complex and ͑b͒ ABHTMA. The red, gray, and black balls
are N, C, and H atoms in the ABHTMA. The dark green is Al in the alane
component, and the bright green is B in the borane component.
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Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
H335
Al-N
Al-H
B-H
C-H
C-H
C-N
Al-H
3000
2500
2000
1500
1000
700
Wavenumber (cm-1)
Figure 5. The IR absorption spectrum of molecules coming out of the hot-
wall reactor at 40°C.
groups on a trimethylamine ligand creates variation in stretching
vibration of C–H features. Also, normally, the lowering of the inten-
sity of CH3 groups or the shift of peak location from CH3 to CH2 is
caused by the precursor decomposition.22
In the case of the C–N stretching features, the intensities of peaks
at 2834 and 2775 cm−1 increased with the increase in temperature
up to 200°C. To investigate the reason, we have taken the IR spec-
trum of the similar molecules, DMEAA ͑Fig. 7a͒ and trimethyl-
amine ͑Fig. 7b͒. In the case of the two molecules, the intensity of the
C–N stretch mode is similar to that of the C–H stretch mode. How-
ever, after the trimethylamine was bonded with the alane-borane
complex, the intensity of the C–N stretching feature of ABHTMA
shown in Fig. 5 is much lower than that of the C–H. It is believed
that the bonding of borane makes the intensity of the C–N stretching
features in the range of 2750–2850 cm−1 lower. So, the bond break-
ing between alane and borane by thermal energy would increase the
intensity of the C–N stretching features. This can be identified in
Fig. 6b.
Figure 3. ͑Color͒ The calculated formation energies of various molecules
composed of alane, borane, and trimethylamine are plotted as a function of
alane chemical potential ͓␮͑AlH3͔͒. The trimethylamine-rich condition is
considered, in which the ABHTMA molecule is stable.
Figure 6c shows the variation of peak intensity ͓1793 ͑peak A͒
and 1844 cm−1 ͑peak B͔͒ and generation of the peaks ͑1892 and
1882 cm−1͒ related to Al–H stretching features over the reactor wall
temperature of 150°C. This means that thermal energy from the hot
ABHTMA
( AlH3-x
)
(x/2 H2)n
+
n
(x= 0 ~ 3)
H
Aluminum particle
H
H
H
CH3
CH3
CH3
Gas phase
Dissociation
CH3
CH3
B
Al
H
N
BH3
N
H
CH3
Figure 4. Schematic diagram of the
chemical reaction in the gas phase and on
the surface.
Surface reaction
H2
CH3
amine-borane complex
H
H
CH3
BH3
N
CH3
CH3
Al
B
N
H
H
H
H
CH3
CH3
Al film
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H336
Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
ated two peaks only give information about oligomerized forms of
alane. The alane dissociated from ABHTMA is easily oligomerized
due to the high degree of intermolecular association of Al–H
molecules.23 When observing the two main peaks related to an Al–H
vibrational feature, peak A was decreased and peak B was fluctuated
as the deposition temperature was increased. Peak B showed a de-
cline up to 140°C. However, the intensity at 150°C got higher than
that observed at 140°C. In the temperature range of 160–200°C, the
intensity was decreased again. Around 150°C, the abnormal behav-
ior of peak B was observed, because this peak is correlated with the
generated Al–H stretching feature. We found that new peaks at 1882
and 1892 cm−1 started to be generated over 150°C, and then the
intensity of peak B was increased. Thus, it is believed that the newly
generated peaks are related to the oligomerized forms of Al–H mol-
ecules dissociated.24 The intensity of the new peaks is much smaller
than that of peaks A and B. This means that the amount of oligo-
merized forms of alane is small.
C-H
C-N
(a)
(b)
C-H
125oC
125oC
200oC
200oC
125oC
125oC
200oC
125oC
1520 1500 1480 1460 1440 1420
3000 2950 2900
2850
2800 2750
Al-H
(c)
125oC
Peak B
Peak A
Figure 8 shows the A–H peak variation as a function of the
pressure at a fixed temperature. At 125°C, both peaks ͑A and B͒
increased with the increase in reactor pressure. It means the addi-
tional decomposition of ABHTMA is not happening in the gas phase
at temperatures as low as 125°C. In the temperature range of
140–200°C, peaks A and B decreased gradually with increasing
pressure due to the decomposition of ABHTMA. However, the de-
crease rates of peaks A and B were different. The decrease rate of
peak A was faster than that of peak B, because the mixed informa-
tion about various Al–H stretching features is shown together at the
position of peak B. The intensity of peaks generated at 1882 and
1892 cm−1 in the range of 150–160°C was increased with the in-
crease in reactor pressure. However, in the range of 175–200°C, the
peaks fluctuated with the pressure range. The peak increased at the
pressure of 0.65–0.95 Torr but decreased at the pressure of
0.95–2.5 Torr. This means that oligomerized forms are sensitive to
the pressure and the reactor temperature.
150oC
140oC
160oC
150oC
200oC
1800
1860
1840
1820
1800
1780
Wavenumber (cm-1)
Figure 6. FT-IR spectra of ͑a and b͒ C–H, ͑b͒ C–N, and ͑c͒ Al–H stretching
features as a function of the hot-reactor-wall temperature.
It is believed that the Al–H stretching peaks give us valuable
information on the reaction mechanism in the gas phase. With the
area ratio of integrated absorbance of peaks A and B at various
temperatures and pressures, the degree of dissociation of ABHTMA
can be known. The variation of the area ratio of Al–H stretching
features as a function of the reactor pressure is shown in Fig. 9. The
initial value of the area ratio ͑peak B/peak A͒ is 0.36, and the ratio
does not change because additional decomposition of ABHTMA
does not happen under 125°C at the full range of the reactor pres-
sure. However, at 140°C, the ratio is gradually increased over
0.95 Torr. This means that the decrease rate of peak A was faster
than that of peak B and the dissociation of ABHTMA took place fast
over 0.95 Torr. At 150°C, the increase rate of the ratio over 0.7 Torr
got faster. And, the rate increased rapidly even at pressure as low as
0.45 Torr at 160°C. With these results, we can see that the variation
of Al–H stretching features are sensitive and reactive to the analysis
conditions, especially in the range of 150–160°C.
wall has an effect on the dissociation and decomposition of
ABHTMA and the Al–H stretching features are sensitive to the
transmission of thermal energy controlled by the wall temperature
and the reactor pressure. Peak A only gives information about the
Al–H vibrational feature of alane bonded with borane and trimethyl-
amine. Peak B gives mixed information about Al–H features of
alane itself and oligomerized forms of alane. And, the newly gener-
Figure 10 shows the B–H stretching features as a function of the
pressure at the fixed temperature. At temperatures as low as 125°C,
the pressure increase resulted in an increase in absorbance for B–H
of ABHTMA ͑peak C͒ and borane-trimethylamine ͑peak D͒. The
increase rate of the integrated absorbance ratio raised slightly with
the increase of pressure as shown in Fig. 11. This is not due to
additional decomposition with increasing pressure but to the addi-
tional recombination between borane and trimethylamine. If addi-
tional decomposition of ABHTMA was happening, the intensity of
the Al–H stretching features shown in Fig. 8 should be decreased
together. At 140°C, peak C was decreased by lowering the
ABHTMA concentration. Meanwhile, peak D was increased rapidly
by the recombination of borane and trimethylamine. In the case of
B–H stretching features observed at 175°C, the peaks related to a
borane-trimethylamine complex were only observed in the full pres-
sure range. Over 175°C even at low pressure, the ABHTMA was
fully dissociated and recombined. So, the Al–H and B–H stretching
features of ABHTMA located at the original position disappeared
(a)
(b)
3500 3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Figure 7. The IR absorption spectrum of ͑a͒ DMEAA and ͑b͒ trimethyl-
amine.
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Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
H337
0.65 Torr
Peak A
125oC
140oC
2.50 Torr
0.60 Torr
2.50 Torr
Peak B
0.60 Torr
0.60 Torr
1820
1760
1900
1820
1760
1900
160oC
0.60 Torr
150oC
0.60 Torr
0.60 Torr
0.60 Torr
2.50 Torr
Figure 8. IR spectra of Al–H stretching
features as a function of the pressure at a
fixed temperature.
1820
1760
1900
1820
1760
1900
0.95 Torr
0.65 Torr
0.95 Torr
0.65 Torr
2.5 Torr
0.60 Torr
175oC
200oC
0.60 Torr
1820
2.5 Torr
1900
1820
1760
1760
1900
Wavenumber (cm-1)
Wavenumber (cm-1)
and then were generated at the new position, which is related to
oligomerized forms of an alane molecule and
trimethylamine complex, respectively.
a borane-
2.0
Figure 11 shows the variation of the area ratio of integrated ab-
sorbance of peaks C and D as a function of the reactor pressure. The
ratio was changed abruptly over 140°C, and the increase rate was
faster over 0.95 Torr. Over 160°C, the ratio increased rapidly at
pressures even as low as 0.65 Torr. This means that peak D is more
sensitive to the change of ambient conditions than peak C. And, the
peak is valuable to monitor the deposition process and the status of
the precursor, because the ratio represents the decomposition rate of
ABHTMA or the recombination rate of the borane and trimethyl-
amine molecules, and the borane-trimethylamine complex ͑peak C͒
is the by-product ͑or the complex͒ generated after decomposition or
dissociation of ABHTMA.
Figure 12 shows FT-IR spectra of ABHTMA adsorbed on the
sample coated with Al metal deposited by CVD as a function of the
temperature and dosing time. At temperatures as low as 80°C ͑Fig.
12a͒, ABHTMA dosed to the grid was stacked on the surface.
Though the intensity of the peaks increased with dosing time, the
peaks disappeared after 12 min without dosing. This is because most
of the ABHTMA molecules were physisorbed on the Al metal sur-
face at temperatures as low as 80°C. We also observed that the
100oC
125oC
140oC
150oC
160oC
1.5
1.0
0.5
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Hot Wall Reactor Pressure (Torr)
Figure 9. Area ratio of integrated absorbance of Al–H stretching features
͑peak B at 1844 cm−1/peak A at 1799 cm−1͒.
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H338
Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
10
125oC
B-H
100oC
125oC
140oC
150oC
160oC
9
8
of borane-trimethylamine
(PPeak D)
7
6
5
4
3
2
1
0
of ABHTMA (Peak C)
2.5 Torr
0.65 Torr
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2520
2460
2400
2400
2400
2340
Hot Wall Reactor Pressure (Torr)
Figure 11. Area ratio of integrated absorbance of B–H stretching features
͑peak D/peak C͒.
140oC
2.5 Torr
stretching features were observed at a similar position when com-
pared with two spectra ͑Fig. 13b and c͒. Especially, the B–H stretch-
ing features were shifted to a lower frequency, and the ratio of
intensity of B–H and Al–H stretching features was bigger than the
ratio in Fig. 13c. We believe that it is on account of the interaction
among the borane-trimethylamine, of which the interaction between
Al metal surface and the adsorbed molecule could be causing the
change in frequencies and intensities. When ABHTMA was dosed at
125°C, the Al–H stretching features in the range of
1795–2000 cm−1 and C–H stretching features in the range of
1400–1500 cm−1 were observed. The Al–H and C–H stretching fea-
tures remained on the surface due to the incomplete reaction of the
dosed ABHTMA, which represent the source of the carbon contami-
nation incorporated into the films. Meanwhile, the peak related to
B–H was not observed. This is because of the high vapor pressure
͑0.8 Torr at 23°C͒ and high stability of borane complex ͑easy de-
sorption͒. The decomposition characteristics of borane-
trimethylamine were already reported. The borane-trimethylamine
complex was used to deposit the boron-carbonitride films in the
temperature range of 500–700°C.25 When the ABHTMA was dosed
at 150°C ͑Fig. 12c͒ the peaks were not observed. This means that all
kinds of molecules were adsorbed and then all kinds of by-products
were desorbed at this temperature, which affected the film quality.
The film deposited in this region ͑around 150°C͒ has the best film
properties with respect to surface roughness, reflectance, and
resistance.4 It is good evidence that there is a strong relationship
between deposition characteristics and the inspection result of mol-
ecules adsorbed and desorbed.
0.65 Torr
0.65 Torr
2520
2460
2340
175oC
Conclusion
The study on the behavior diagnosis of ABHTMA in the gas
phase and on the surface was successfully carried out using a modi-
fied FT-IR spectroscope. The alane-borane-trimethylamine complex
was found to be the most stable when the trimethylamine concen-
tration was high and the alane and borane concentrations were simi-
lar to each other. By reducing the alane concentrations, the borane-
trimethylamine complex could be generated as a by-product, as
observed in the FT-IR measurements. It was observed that the C–H,
C–N, Al–H, and B–H stretching features were sensitive to change in
measurement conditions such as wall temperature and pressure. The
intensity of most C–H stretching features was decreased with the
increase in wall temperature due to the partial decomposition of
ligands. The intensity of C–N stretching features showed different
behavior with temperature change compared to that of C–H features.
The intensity of C–N peaks was increased with the increase in tem-
perature by the dissociation of borane. Especially, the B–H and
2520
2460
2340
Wavenumber (cm-1)
Figure 10. IR spectra of B–H stretching features as a function of the pres-
sure at a fixed temperature.
absorbance peaks of physisorbed ABHTMA were similar to
ABHTMA in the gas phase, as shown in Fig. 13. Thus, the phys-
isorbed ABHTMA was purged, and the peaks disappeared as time
passed. Figure 13b and c shows the IR spectra of ABHTMA ad-
sorbed on the surface at 80°C and ABHTMA taken in gas cell at
80°C, respectively. The peak positions of Al–H, C–H, and C–N
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Journal of The Electrochemical Society, 156 ͑5͒ H333-H339 ͑2009͒
H339
(a)
Al-H
Al-H
C-H B-H
C-H
C-H
C-H C-N
B-H
1min dose
5min dose
(a)
(b)
10min dose
3min waiting
3min waiting
3min waiting
3min waiting
(c)
3000
2800
2600
2400
2200
2000
1800
1600
1400
3200 2800 2400 2000 1600 1200
Wavenumber (cm-1)
(b)
Al-H
C-H B-H
C-H
Figure 13. Comparison of spectrum taken ͑a͒ at the surface temperature of
125°C, ͑b͒ at the surface temperature of 80°C, and ͑c͒ at the gas-cell tem-
perature of 80°C.
1min dose
5min dose
isorbed at temperatures as low as 80°C was almost purged from the
surface, so the deposition did not happen. The species adsorbed at
125°C was chemisorbed and, by surface reaction the Al film was
deposited. But, the film purity was not good due to the incorporation
of carbon by the imperfect desorption of the molecules or by-
products adsorbed on the surface. We also observed the C–H stretch-
ing feature around 1500 cm−1 acting as a carbon source. At tempera-
tures as high as 150°C, any stretching features were not observed.
10min dose
3min waiting
9min waiting
Korea Research Institute of Standards and Science assisted in meeting
the publication costs of this article.
3200 2800 2400 2000 1600 1200
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(c)
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