22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Polymer film deposition of TMDSO using an atmospheric pressure DBD plasma
jet
C. Vivien1, E. Robert2, P. Supiot1 and J.-M. Pouvesle2
1
Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN) - UMR CNRS 8520, Université Lille I Sciences et Technologies, Villeneuve d’Ascq, France
2
GREMI – UMR CNRS 7344, Université d’Orléans, Orléans, France
Abstract: The present work deals with plasma polymerisation of TetraMethylDiSilOxane
with a Dielectric Barrier Discharge plasma jet at atmospheric pressure. Depending on
parameters like voltage, frequency, carrier gas and monomer injection, the deposited
polymer appears either as a gel-like coating or a transparent film with fringes. Deposits are
characterized by Fourier Transformed IR spectroscopy and contact angle measurements.
Keywords:
atmospheric pressure DBD plasma jet, low temperature, plasma
polymerisation, tetramethyldisiloxane
1. Introduction
Plasma Enhanced Chemical Vapour Deposition
(PECVD) processes have been used for decades for
surface processing in a wide range of industrial
applications like semiconductor films, low-k films, barrier
diffusion, protective coatings, adhesion layers,
hydrophilic or hydrophobic layers, etc... Most of these
processes are usually realized under low pressure.
Actually, a great and increasing interest in the
development of plasma sources operating at atmospheric
pressure (AP), firstly for easy surface treatments [1],
offered the capability to develop PECVD under AP and
non-thermal conditions. Such processes have been studied
intensively focusing mainly on polymers, oxides, and
carbon materials using common gases (He, Ar, N 2 , air,
CxHy…) and liquid monomer sources [2-5]. According to
a specific purpose, any specific monomer can be selected
and can be more or less preserved according to the power
input in the plasma. Plasma polymerisation offers many
possibilities of applications and intensive research is still
running on this subject.
The Atmospheric Pressure Dielectric Barrier Discharge
(AP-DBD) Plasma Gun device, developed by GREMI
laboratory, allows rare gas plasma propagation along
small tubes and was firstly reported for biomedical
purposes [6]. This device shows several advantages with
respect to other excitation systems: a) much smaller rare
gas flow-rates, b) the possibility to separate the plasma
source from the injection mixing point of admixed gases
(nitrogen or oxygen) or precursor vapour allowing an
enhanced discharge stability, c) good gas mixing
properties favouring significant precursor flow-rates for
the forthcoming polymerization.
This work deals with plasma polymerisation of
TetraMethylDiSilOxane (TMDSO) with the AP-DBD
Plasma Gun. Deposited layers are characterized by FTIR
and contact angle measurements.
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2. Experimental set-up
The AP-DBD Plasma Gun device used in this work was
previously described and studied in details [6,7].
The plasma discharge is ignited in Helium under a
constant flow rate of 1 slpm.
The precursor used was the TetraMethylDiSilOxane
(C 4 H 14 Si 2 O, 97%, Sigma Aldrich) was introduced in
either liquid or gaseous state:. The liquid TMDSO flow
rate was regulated by a peristaltic pump (Ismatec) while
its vapour flow was ensured by bubbling nitrogen or
oxygen with a fixed flow rate of 10 sccm. Microscope
slides and polished Silicon wafer (100) were used as
substrates. The process parameters are listed in Table 1
Table 1. Process parameters
Precursor introduction
Liquid
Gaseous
14
14-20
0.5 ; 1; 2
0.5 ; 1 ; 2 ; 4
Helium (slpm)
1
1
Nitrogen or oxygen (sccm)
/
10
Precursor (µL.min-1)
27 ; 54
/
Deposition time (min)
5 ; 10
5 ; 10
6
3 ; 6 ; 9 ; 12
Voltage (kV)
Frequency (kHz)
Distance from the substrate
(mm)
Deposits were analysed by FTIR with a Perkin Elmer
2000 spectrometer. Spectra were performed in the
wavenumber range 4000-400 cm-1 with a resolution of 4
cm-1. Contact angle measurements with water were
carried out on the coatings using the static contact angle
measurement with a PGX-plus goniometer.
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polymerization can be seen through the presence of the
broad band located between 1200-1000 cm-1, which is
assigned to Si-O-Si asymmetric stretching mode. Then, a
broad band around 3400 cm-1 shows the presence of OH
stretching mode in Si-OH or H- bonded OH. [8]
The IR spectrum of the deposited film with the APDBD Plasma Gun is very similar to those obtained in case
of RPECVD at low pressure by Abou Rich et al.[9]. In a
critical review, Merche et al. [3] underlined that different
studies concluded that both methods lead to similarly
deposited films properties.
ν(Si-O-Si), ν(Si-O-C)
Polymer film
TMDSO
ρ(CH3), ν(Si-C)
δ(CH3)s
ν(Si-H)
A (a.u.)
3. Results and Discussion
Visual aspect of the films
The visual aspect of the deposited films depends on the
deposition conditions. Three different types can be
observed: translucent like frozen gelatin (Figure 1a), with
a mixing of fringes and translucent form (Figure 1b) and
transparent with thickness fringes (Figure 1c). In all cases,
the films are not homogeneous in thickness, with the
appearance of fringes and a highest thickness at the
centre, decreasing to the edge.
In both cases of monomer introduction (liquid or
gaseous), increasing of the frequency makes the deposit
more translucent like frozen gelatin and the deposited area
increases with both process duration and the voltage. The
introduction of the monomer in liquid phase induced more
inhomogeneity of the deposit, compared to the films
deposited with gaseous TMDSO injection.
The polymerized coatings have been obtained at 500Hz
in pure Helium with liquid TMDSO, and at 1 kHz with
gaseous TMDSO, for a 10 minutes deposition duration
and plasma tube edge-to-substrate distance ranging from
6 to 9 mm.
ν(CH3)as
ν(O-H)
δ(CH3)as
ν(CH3)s
4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800
600
400
-1
Wavenumber (cm )
(a)
(b)
(c)
Figure 1. Visual aspect of the deposited films (a)
translucent like frozen gelatin, (b) and (c) transparent
with thickness fringes.
Measurements of the films thicknesses have been
performed with a profilometer. A thickness of 1 µm is
reached at the middle of the deposit for the sample of
shown in Figure 1c,
FTIR analysis
IR absorption spectroscopy was used to obtain
information on chemical bonds present in the deposited
films. The Figure 2 show FTIR spectra corresponding to
the TMDSO monomer and a film deposited under the
following conditions: 14 kV, 1kHz, gaseous TMDSO,
10sccm N 2 , a distance of 9 mm and a deposition duration
of 5 min.
IR spectrum of deposited film has absorption peaks
common with those of the TMDSO monomer. This can be
seen with the strong presence of methyl groups: the
asymmetric and symmetric C-H stretch at 2960 and 2910
cm-1 respectively, the -CH 3 asymmetric and symmetric
bending in Si-CH 3 at 1415 and 1260 cm-1 and two
absorption bands at 900 and 800 cm-1 assigned to the
methyl rocking mode and the Si-C stretching mode in
Si(CH 3 ) 2 and the Si-H stretching mode is observed in the
range 2300-2100 cm-1. The occurrence of the
2
Figure 2. FTIR spectra of the monomer TMDSO and a
film deposited with gaseous TMDSO (see the
corresponding text for conditions).
Contact angle measurements
Contact angle measurements with water have been
made on both the translucent gelatin-like and the
transparent deposited films.
The water contact angle value for a microscope slide
cleaned with ethanol is about 30 degrees. The measured
value on all the deposited layers is varying from 75 to 85
degrees. There is no relation between the visual aspect
and the contact angle value. For example, a film as shown
in Figure 1a can have a contact angle of 85 degrees, while
one as shown in Figure 1c can have a contact angle of 75
degrees, and vice versa. These value variations can be
explained by the inhomogeneity of the deposited films. At
this time, no clear correlation has been established
between the different process parameters and the
measured contact angle values.
The measured values are coherent with the IRTF
analyses: the spectra show a strong presence of methyl
groups which mainly contribute to this moderate
hydrophobic behaviour of the plasma-polymer deposits.
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4. Conclusion
In this presented work, the TMDSO monomer has been
polymerized using an Atmospheric Pressure DBD Plasma
Gun working with Helium, and by varying discharge
parameters. The first aim of this work was to demonstrate
the possibility to deposit plasma polymer with such a
plasma discharge. Deposited films analyses clearly show
the efficiency of this plasma-type to polymerize the
TMDSO and their similarity with those realized under
low pressure RPECVD.
The most interesting deposited films are obtained when
the TMDSO monomer is introduced under gaseous phase:
the homogeneity is better, but the influence of the nature
of the gas for its transport is not evidenced.
More experiments and analyses need to be achieved to
complete these preliminary results.
5. Acknowledgements
The authors would like to thank the so-called “Réseau
Plasmas Froids” French Research Network for its
financial support to this work.
6. References
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[7] FR. WO2009050240 (2009), Centre National de la
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[8] D. R. Anderson, ‘‘Infrared, Raman and UltraViolet
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