05pE08P
真空紫外吸収分光計測用小型マイクロ波プラズマ光源の開発
Development of Coaxial Type Compact Microwave Plasma Light Source
for Vacuum Ultraviolet Absorption Spectroscopy
鄭 霊東1, Xijiang Chang2, 佐々木 浩一3, 永津 雅章1,2
Reitou Tei1, Xijiang Chang 2, Koichi Sasaki3, Masaaki Nagatsu1,2
1

静岡大学工学研究科、2創造科学技術大学院、3北海道大学
Graduate School of Engineering, Shizuoka University, 2Graduate School of Science and Technology,
Shizuoka University, 3Graduate School of Engineering, Hokkaido University

1

1. Introduction
In the industrial applications of dry processing plasmas,
excited atoms or molecules play an important role insurface chemical modification and chemical vapor
deposition(CVD). In the most plasma processing, theexcited atom or molecules is one of important parameterto control the plasma chemical reaction. In our previous
work, O2 and N2 gas mixture surface-wave plasma(SWP) was used for the low-temperature plasma
sterilization of medical instrument[1]. To study the roleof the plasma on the sterilization, the information of
excited neutral atoms or molecules generated by plasma
discharge is inevitably important. The vacuum
ultraviolent absorption spectroscopy (VUVAS) technique
was used to measure the absolute oxygen atom density inprocessing plasma. Its advantage is that the measurement
will cause less interference to plasma.
In this work, we developed the coaxial type compact
microwave plasma light source to measure for the
VUVAS, which is able to measure excited oxygen andnitrogen atoms in nitrogen plasma.
2. Experiments
For the VUVAS method, we developed a compact
plasma light source. The new type microwave induced
plasma (MIP) light source is based on the coaxial type
SWP discharge, driven by 2.45[GHz] microwave up to
100[W]. Figure 1 shows the light source structure andphoto of discharge. With different working gas filled in,many certain emitting lines can be produced for different
purpose.
Gas inlet

Copper electrode covered with quartz
tube(L=160mm, Ø = 3mm)

Emission lines

MgF2 window Pumping

2.45GHzMW

3. Results
In this study, we intend to use the VUVAS method tomeasure the absolute oxygen and nitrogen atom densities
in the O2 and N2 gas mixture plasmas. As references, theemitting lines for oxygen atom density measurement
should select near resonance line which is near 130 [nm].
There are three lines, 130.22 [nm] (3s3S0–2p43P2),
130.49[nm] (3s3S0–2p43P1), 130.60 [nm] (3s3S0–2p43P0)
near resonance line. The absorption of these lines can beused to calculate the oxygen atom density in the SWP.

Fig.2 Light source spectra with O2/Ar discharge
Figure 2 shows the O line emission spectra of lightsource, where light source was operated at pressure of
1[Pa] and gas ratio O2/Ar =1:100 with an incident
microwave power of 75 W.
To check the self-absorption effect on 130.5[nm] line,
we measured the absorption of incident light through
SWPs under the fixed condition (O2 , 0.1[Torr], 600[W])using different light source conditions. We found that withlower power and lower pressure conditions, theabsorption at 130.5 nm kept almost constant. It seems thatthe self-absorption can be ignored by controlling the lightsource operating conditions. We obtained the oxygen
atom density in the pure O2 plasma from 0.6x1012 to
1.1x1012 cm-3 when the incident power changed from 300
to 900 W at pressure of 13.3 Pa. Present results revealed
that the oxygen atom densities in N2/O2 SWPs are clearlycorrelated with the etching phenomena of the sporesobserved in the previous sterilization experiments.[1]Reference

Fig.1 Structure of the MIP light source[1]Y. Zhao, A. Ogino, M. Nagatsu, Jpn. J. Appl. Phys.: 42 (2011)
08JF05.