26pC07
大気圧マイクロ波放電による長尺ラインプラズマの生成と基礎特性
Production of long-scale line plasma excited by atmospheric-pressure
microwave discharge and its characteristics
鈴木陽香1, 中野優1, 伊藤仁2,3, 関根誠1,2, 堀勝1,2, 豊田浩孝1,2
Haruka Suzuki1, Suguru Nakano1, Hitoshi Itoh2,3, Makoto Sekine1,2, Masaru Hori1,2,and Hirotaka Toyoda1,2
名大工1, 名大工プラズマナノ2, 東京エレクトロン3
Nagoya Univ.1, PLANT, Nagoya Univ.2, Tokyo Electron Ltd.3
1. Introduction
Recently, atmospheric-pressure (AP) plasmas havebeen given much attention because of its cost benefit
and a variety of possibilities for industrial applications
such as low temperature and large-area surface
treatment.
Among various AP plasma sources,
microwave plasma produced inside slotted waveguide
antennas is attractive because this plasma source caneasily realize non-thermal, stable, and high-density
plasma and we have proposed a newly-designed AP
microwave line plasma source composed of a loop
waveguide and a circulator that utilizes not standing
wave but travelling wave in the waveguide. By
using this plasma source, it was demonstrated thatspatially uniform AP line plasma of 40 cm length wasrealized with helium gas and two different types ofplasma mode were observed by a high-speed camera
under different discharge conditions such as slot gap
width and microwave power. “Pseudo” line plasmamode, i.e., plasma movement along the slot, changed
into “real” line plasma mode, i.e., spatiotemporally
uniform plasma along the slot, by reducing the slot
gap width and increasing the peak microwave
power.[1] To understand mechanism of the twomodes, plasma behavior was observed using thehigh-speed camera in detail and simulated using
electromagnetic (EM) field simulation software andone-dimensional diffusion model including spatial
distribution of the ionization rate in one moving
plasma.
2. Experimental
Pulsed-microwave power (pulse-frequency: 20 kHz,duty cycle: 20-100%, peak power: 1.0 kW) was
supplied to the loop waveguide through an EH tuner.
A section of the loop waveguide with a long slot (60cm length, 0.1-0.7 mm width, 1.0 mm thickness)connected to a vacuum chamber was vacuum-sealedby two airtight windows and evacuated by a rotarypump.
After the evacuation, helium gas wasintroduced into the vacuum-sealed part through small
holes on the waveguide wall at total flow rates of 5.0
slm to fill the chamber and the waveguide at apressure of 100 kPa.

3. Results and Discussions
The plasma looked spatially continuous along theslot in time average, but was discrete in wide gap
width (>0.2 mm) under low duty cycle condition(“pseudo” line mode). Under 0.1 mm gap widthcondition, the plasma speed and size increased at ahigh duty cycle (>80 %) and plasma became spatiallycontinuous inside the slot (“real” line mode). Figure
1 shows a phot of plasma emission in the “real” line
plasma mode. Although there is emission intensity
fluctuation near the both slot edges, high uniform andcontinuous line plasma is realized. To find out thecause of the fluctuation, EM simulation in the slotwith plasma was performed. Figure 2 shows thesimulated distribution of electric field intensity along
the slot. For the most part of the slot, electric fieldremains stable, but a slight fluctuation in the vicinityof the slot edges is observed, suggesting that smallreflection power generated at the slot edges disturbs
electric field in the vicinity of the edges. I willreport about the “pseudo” mode including themechanism in my presentation.

Fig. 1. Phot of plasma emission in the “real”
line mode.

Fig. 2. Simulated distribution of electric field
intensity.

Reference[1] H Suzuki et al.: Appl. Phys. Express 8 (2015)
036001.
Acknowledgement
Part of this work was supported by a JSPS
Grant-in-Aid for Scientific Research (B) 25286079.