23P005-O
Fabrication of Si based Microchannel by Ar/F2 Vapor Etching andPlasma Etching
Ar/F2 気相エッチングとプラズマエッチングによるSi マイクロ流路構造の形成
Akihiro Matsutani1, Ayako Takada2
松谷晃宏 1，髙田綾子 2
1Center for Semiconductor and MEMS Processes, Technical Department, Tokyo Institute of Technology
R2-3, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 Japan
東京工業大学 技術部 半導体・ＭＥＭＳ支援センター，〒226-8503 横浜市緑区長津田町 4259, R2-3
2Bio-Technical Center, Technical Department, Tokyo Institute of Technology
B-41, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501 Japan
東京工業大学 技術部 バイオ技術センター，〒226-8501 横浜市緑区長津田町 4259, B-41We demonstrated the fabrication of Si based multistep microchannel without cover plates by Ar/F2
vapor etching and Cl2-inductively coupled plasma (ICP) etching process. We think that the proposed
microchannel would be also useful for single bacterial cell analysis.

1. Introduction
The microchannel is widely used as micro total
analysis systems (μ-TAS) in chemical andbiological analysis. The typical size of them isapproximately 50-100 μm in width and depth.
However, the microchannel of submicron size
would be needed for investigation of capillary
vessel, analysis of single virus particles and soon. Almost microchannels are fabricated by wetetching, plasma etching and lithography process.
It is difficult to fabricate submicron
microchannel by wet etching due to the surface
tension. Therefore, dry etching technique suchas vapor etching or plasma etching is required.
Generally, the vapor etching using XeF2 is also
widely used for Si etching [1-3]. XeF2 is solidand its vapor pressure is approximately 500 Pa
at room temperature. A mass flow controller isnot necessarily available for the XeF2 gas flowrate at such a low pressure of the cylinder. While,
Ar/F2 gas can be supplied from cylinder and its
pressure is high enough for operation of themass flow controller. On the other words, theetching process of Si can be controlled by gas
flow rate and process pressure as etchingparameters.
In this paper, we demonstrate fabrication of Si
based microchannel by Ar/F2 vapor etching, andplasma etching process for flatten of the etchedchannel bottom.

2. Fabrication of Microchannel by Ar/F2Vapor Etching
We used electron beam lithography system(Elionix ELS6600) and positive type electron
beam resist ZEP520A for mask patterning ofmicrochannel. We also used Ar/F2 (Ar: 90%, F2:10%) as an etching gas. Figure 1 (a) and 1(b)show a schematic diagram of fabrication process
Submicron Gap

Resist Mask

(a)

(b)
Fig. 1 Schematic diagram of fabrication process(a) and SEM image of microchannel fabricatedby Ar/F2 vapor etching process (b).

Pure
Water

Microchannel

10μmFig. 2 Optical microscope image (Top View)
of Si microchannel fabricated by Ar/F2 vaporetching.

Fig. 3 SEM image of Si-microchannel byAr/F2 vapor etching and Cl2-ICP etchingprocess.

and an SEM image of a microchannel fabricatedby Ar/F2 vapor etching process, respectively.
The Ar/F2 flow rate was 100 sccm and theprocess pressure was kept at 1×103 Pa. The gapof resist mask pattern was 200nm. The etcheddepth was about 1.7μm. It is found that the resist
mask of upper side of microchannel was warped
up due to the stress.
Figure 2 shows an optical microscope image(Top View) of Si microchannel fabricated byAr/F2 vapor etching. The flowing direction ofpure water was from left to right. The resist gap
was 0.7μm and 0.8μm. Pure water wasintroduced by capillary forces. Despite the gap
on the top of the microchannel, it is found thatwater flows from left to right without flowing
out. We think that the proposed microchannel
can be applied to mixing micro fluidic devices
between vapor and liquid. This proposed manner
is a simple technique without process forcovering on the microchannel.

4. Conclusions
We demonstrated the fabrication of Si based
multistep microchannel without cover plates by
Ar/F2 vapor etching and Cl2-ICP etching process.
We think that the proposed microchannel would
be also useful for single bacterial cell analysis.

3. Fabrication of Step type Si-Microchannel
by Plasma Etching Process
Figure 3 shows an SEM image ofSi-microchannel by Ar/F2 vapor etching andCl2-ICP etching process. We used a reactive ion
etching system (Samco RIE-101ip) and Cl2 as anetching gas. ICP/Bias RF power was 300/20 W,
Cl2 flow rate was 2 sccm. It is found that theresist mask was remained on the Simicrochannel and narrow vertical microchannel
was formed in the cylindrical microchannel. Wethink that this microchannel structure is usefulfor isolation of bacterial cells.

Acknowledgment
This work was supported by a Grant-in-Aid for
Scientific Research (C) #23510141 from the
Ministry of Education, Culture, Sports, Scienceand Technology.
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