22P061-P
Chemical Modification of Polymer Surface Using Large-area Plasma
Excited by 915MHz UHF Wave
915MHzUHF波励起大面積プラズマを用いたポリマー表面の化学修飾
Kazuki Kunii1, Akihisa Ogino1,2, and Masaaki Nagatsu1,2
國井 一輝1, 荻野 明久1,2, 永津 雅章1,2
1

Graduate School of Engineering, Shizuoka University, 3-5-1, Johoku, Hamamatsu 432-8561, Japan1
静岡大学大学院工学研究科電気電子工学専攻，〒432-8561 浜松市城北3-5-1
2Graduate School of Science and Technology, Shizuoka University, 3-5-1, Johoku, Hamamatsu 432-801 1, Japan2
静岡大学創造科学技術大学院，〒432-8011 浜松市城北3-5-1
In this study, we developed the large-area surface-wave plasma device with a resonance cavity at 915MHz,
where we investigated the optimization of launcher structure for achieving uniform plasma by making useof the 3D finite difference time-domain(3D-FDTD) method and carried out the Langmuir probe
measurements of plasma density distribution. The preliminary results of the amino group addition ontopolymer surface by Ar and NH3 gas mixture plasma were also given.

1. Introduction
Recently, the development of the plasma
equipment for the large-area process is strongly
demanded because of an increase in demand forlarge-scale display panel and solar battery and also
the enlargement of processing size for improving
productivity and lowering the cost. The surface
wave plasma using 2.45 GHz microwave has great
advantages for making high-density plasma withoutmagnetic field, but it is often difficult to makeuniform plasma in a large-area. Here, we used 915
MHz UHF wave which has some advantages. First,
the free space wavelength ratio increases by a factorof about 2.7 compared with the 2.45 GHz
microwave, so making large-area plasma will beeasy. Second, it is possible to control plasma fromlower electron density, owing to the cutoff density(1.0×1010 cm-3) can be lowered by a factor of 7compared with the 2.45 GHz microwave (7.0×1010cm-3).
To enlarge plasma size, there is a problem of
dielectric window plate to avoid it braking by ahuge mechanical force between low pressure andatmospheric pressure. To overcome this issue, we
proposed to use smaller dielectric windows which
are arranged at appropriate positions as UHF wavelauncher.
In this study, we developed the 915MHz UHF
wave excited large-area surface-wave plasma
device with a resonance cavity. To optimize thelauncher structure for achieving large-area, uniform
plasma, we carried out the field distribution
analysis using the 3D finite differencetime-domain(3D-FDTD) method and the Langmuirprobe measurements to study the density profiles.

2. Experimental setup
A schematic drawing of 915 MHz surface wave
plasma device is shown in Fig. 1. The resonancecavity was 800 mm in diameter and 60 mm inheight. The dielectric window plates made of quartz
were separately located on bottom of the resonancecavity as shown in Fig. 1.

Fig. 1 Schematic diagram of 915 MHz surface wave
plasma device.

The numerical analysis of electromagnetic-fieldin the resonance cavity was carried out with 3DFDTD calculation code which we had developed[1]. The wave guide and the resonance cavity weredefined by the space steps Δx, Δy and Δz as 5 mm
to satisfy the convergence conditions of FDTD
analysis.
The distributions of the ion saturation current inAr/NH3 gas mixture plasma were measured along
the radial direction of 45 degrees against the x axis
for z=240 mm at different gas mixture ratios.
The polyethylene (PE) sheets were placed on thestage inside chamber at z=240 mm. The total gas
pressure and flow rate of Ar/NH3 were kept at 8 Pa
and 100 sccm, respectively. NH3 gas was3. Results
Figure 2 shows the 3D-FDTD calculation resultsof the spatial distributions of electric field intensity
along z axis on bottom of the resonance cavity.
Here, 915 MHz UHF wave introduced through theslot antennas from the waveguide to a resonancecavity distributed certain mode pattern with theazimuthal mode number of m=4, radial mode
number of n=1 and axial mode number of p=0
inside the resonance cavity, which is identified as
TM410 mode. Moreover, we also confirmed that theresonant mode of the present cavity structure was
TM410 mode according to the resonance cavity
theory. From these theoretical expectation, thequartz plates were arranged on the cavity bottom
plate to fit TM410 mode, as shown in Fig. 2.

QuartzWindowFig. 2 The electric field intensity on cavity
bottom plane calculated by using 3D-FDTD.

Figure 3 shows the distributions of the ion
saturation current along the radial direction in
Ar/NH3 plasma. In the case of 100% Ar gas, the ion
saturation current was higher than that of gas
mixture case, and the electron temperature wasabout 1.5 eV along the radial direction. When NH3gas ratio was set to 3%, the uniform plasma wasobtained within a radius of roughly 25 cm.
Furthermore, when NH3 gas ratio was increased to5%, uniformity of the density profile slightly
became better, while the ion saturation current
decreased.
Figure 4 shows the XPS result in wide spectra
for derivatized PE samples. F 1 peak (around 690eV) was observed on the plasma treated surface.

2Ion saturation current Isat (mA/cm )introduced to introduce the amino group on thesurface. The surfaces of treated samples wereanalyzed by XPS. Amino group introduced onpolymer surface was estimated by chemical
derivatization method using 3-trifluoromethyl
benzaldehyde (TFBA) of methanol solution (0.1M/15ml). Fluorine atoms of TFBA have beenutilized to label of primary amino group (–NH2)
among other groups [2].

321

Ar : 100%

Ar:97%, NH3:3%

Ar:95%, NH3:5%
0010203040Position r (cm)Fig. 3 The distributions of the ion saturation current
along the radial direction in Ar+NH3 plasma.

This peak was resulted from the introduced
primary amino groups. The relative concentrationof primary amino group (-NH2/C) and theselectivity (-NH2/N) was estimated from F 1s peak.
[2]. The estimated -NH2/C and -NH2/N was 0.88%
and 24.5% respectively.

Fig. 4 Wide XPS spectra of untreated (bottom) andAr/NH3 plasma treated (top) samples.

4. Conclusion
In this study, we developed the large-area
surface-wave plasma device with a resonance cavity
at 915MHz. We investigated the optimization oflauncher structure for achieving uniform plasma bymaking use of the 3D-FDTD method and carriedout the Langmuir probe measurements of plasma
density distribution. After optimizing the launcher
structure, we obtained the large-area uniform
plasma within a diameter of roughly 25 cm. We alsopresented the preliminary results of the aminogroup addition onto polymer surface.
References[1] A. Ogino, K. Naito, F. Terashita, S. Nanko and M.
Nagatsu: J. Appl. Phys. 44 (2005) L352
[2] S. Noguchi, A. Ogino, M. Nagatsu: Proc.
PSS-2009/SPP-26, Nagoya, 2009 p461