24P015-O
Influence of Nano-particles on Multi-hollow Discharge Plasmas for
Microcrystalline Silicon Thin Film Deposition
微結晶シリコン薄膜作製用マルチホロー放電プラズマに対するナノ粒子の影響
Takeaki Matsunaga, Yeonwon Kim, Kazunori Koga, Hyunwoong Seo, Giichiro Uchida,
Kunihiro Kamataki1, Naho Itagaki2, and Masaharu Shiratani
松永剛明, 金 淵元，古閑一憲，徐 鉉雄，内田儀一郎，
鎌瀧晋礼1，板垣奈穂2，白谷正治
Graduate School of Information Science and Electrical Engineering, Kyushu University
744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan1
Center for Research and Advancement in High Education, Kyushu University, Fukuoka 819-0395, Japan
2PRESTO, Japan Science and Technology Agency, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
九州大学大学院システム情報科学府 〒819-0395 福岡市西区元岡7441
九州大学高等教育開発推進センター 〒819-0395 福岡市西区元岡744
2JSTさきがけ 〒102-0075 東京都千代田区三番町5
Effects of nano-particles on formation kinetics of microcrystalline silicon films were studied by X-ray
diffraction spectroscopy (XRD) and optical emission spectroscopy (OES). Volume fraction of (220)orientation crystals of films without incorporating nano-particles is higher than that of those withnano-particles. The IH/ISi* value in the region with nano-particles is slightly higher than that in the region
without nano-particles. The ISi*/ISiH* value is almost the same as that in the region with and withoutnano-particles. These results suggest that (220) orientation crystal growth is suppressed by incorporation ofnano-particles.

2. Experimental setup
Combinatorial deposition of c-Si:H films wascarried out with a multi-hollow discharge plasma
CVD reactor as shown Fig. 1. H2 dilution ratio R =([SiH4] + [H2])/ [SiH4] was set to be 15, 30, 50, 100
and 300. The total pressures were 2 or 4 Torr. The
peak-to-peak discharge voltage was 80 V and thedischarge frequency was 60 MHz. The reactor
temperature and the quartz glass substratetemperature were set to be 250oC.
Plasma emissions were measured with aspectroscope (ACTON SP2300i).
Crystallinity, XC, and crystalline orientation
were determined with a Raman spectroscope (Jasco,pump

downstream

mesh
film
quartz substrate
grounded substrate holder

nanoparticles

view port
Opticalspectrometer～lensgrounded electrodepowered electrode
discharge region

upstream

1. IntroductionHydrogenated microcrystalline silicon (c-Si:H)
films are key materials for development of Si thinfilm tandem solar cells. High-pressure depletion
method has been proposed to overcome thetrade-off between deposition rate and film qualities[1,2]. A good correlation of (220) preferential
orientation in c-Si:H films with cell efficiencies
was reported [3]. However the mechanism todetermine the crystalline orientation has not beenclarified yet.
We have developed a multi-hollow discharge
plasma CVD method by which incorporation ofnano-particles formed in discharges is considerably
reduced in the upstream region using gas flow thatdrives nano-particles toward the downstream regionof the reactor [4]. To reveal effects of incorporationof nano-particles on the formation kinetics of thec-Si:H films, we have deposited c-Si:H films
with and without nano-particles using themulti-hollow discharge plasma CVD method, andthen we have measured the volume fraction of(220) crystalline orientation of films and plasma
emissions. Here we report these experimentalresults.

gas inlet

radicals

Fig. 1. Schematic of experimental setup.

3. Results and Discussion
TEM observation of nano-particles show that
their mean size is 1.2 nm and 7 nm for P= 2Torrand 4Torr, respectively. They are crystalline.
Figure 2 shows dependence of the volume
fraction of (220) crystalline orientation crystals of
the films with and without nano-particles on thedistance from the electrode. For 4Torr, the volume
fraction of (220) crystalline orientation crystals of
the films without nano-particles is higher than thatwith nano-particles. The same tendency was seen in
the pressure of 2Torr. These results suggest thatcrystalline growth of (220) orientation is interferedbyincorporating
ofcrystalline
siliconnano-particles.
Figure 3 shows dependence of emission
intensity ratio from H(656.3nm) and Si*(288.1nm)
IH/ISi* on H2 dilution ratio R. The IH/ISi* increases
with increasing R and the value in the downstream

I220/(I111+I220+I311)

0.65●: 2Torr upstream○: 2Torr downstream▲: 4Torr upstream△: 4Torr downstream

0.6
0.55
0.5
0.45
0.4

05101520

distance from electrode z (mm)Fig. 2. Dependence of volume fraction of (220)crystalline orientation c-Si:H films on thedistance from electrode. Condition: H2 dilution
ration R=300.
70□：downstream●：upstream

IH/ISi* (arb.units)

60
50□：downstream●：upstream

0.25

0.2

0.15

0.1050 100 150 200 250 300 350

R=([SiH ]+[H2])/[SiH4]4Fig. 4. Dependence of ISi*/ISiH* on the H2 dilution ratio R.

region is higher than that in the upstream region.
The IH/ISi* shows the generation rate ratio of the Hand SiHx radicals. The higher density ratio of[H]/[SiH3] is preferable for crystalline formation.
These results suggest that higher crystallinity films
are obtained in downstream region. Figure 4 shows
dependence of intensity ratio from Si*(288.1nm)
and SiH*(414.0nm) ISi*/ISiH* on H2 dilution ratio R.
The ISi*/ISiH* gives information on the electron
temperature Te. The ratio ISi*/ISiH* decreases withincreasing R. The ratio in the upstream region isalmost the same as that in the downstream region.
Therefore, the electron temperature in the upstream
region is almost the same as that in the downstream
region.
4. Conclusions
We have measured the volume fraction of (220)crystalline orientation crystals of c-Si:H thin films
with and without nano-particles deposited by themulti-hollow discharge plasma CVD method. The(220) orientation of the films without nano-particles
is higher than those with nano-particles. Theseresults suggest that incorporation of nano-particles
tends to suppress (220) orientation crystal growth.
Acknowledgments
This work was partly supported by Core
Research for Evolutional Science and Technology(CREST) by the Japan Science and Technology
Agency (JST).
References

4030201000.3

ISi*/ISiH* (arb.units)

NRS-3100) and an X-ray diffraction (XRD)
spectrometer(Bruker, EMX), respectively.
Nano-particles were trapped on a stainless meshwhich is placed in the downstream region and theirsize and crystallinity were evaluated with atransmission electron microscope (TEM).

050 100 150 200 250 300 350

R=([SiH ]+[H2])/[SiH4]4Fig. 3. Dependence of IH/ISi* on the H2 dilution ratio R.

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