24P010-O
Deposition of Cluster-free A-Si:H Films Using A Cluster-eliminating Filter
クラスター除去フィルタを用いたクラスターフリー水素化アモルファスシリコンの製膜
Kenta Nakahara1, Kosuke Hatozaki1, Yuuji Hashimoto, Takeaki Matsunaga1, Muneharu Sato1,Daisuke Yamashita1, Hidefumi Matsuzaki1, Hyunwoong Seo1, Kunihiro Kamataki2,
Giichiro Uchida1, Naho Itagaki1,3, Kazunori Koga1, and Masaharu Shiratani1
中原賢太1, 波戸﨑浩介1, 橋本優史1, 松永剛明1, 佐藤宗治1, 山下大輔1,松崎秀文1, 徐鉉雄1, 鎌滝晋礼2, 内田儀一郎1, 板垣奈穂1,3, 古閑一憲1, 白谷正治11

Graduation School of Information Science and Electrical Engineering,
Center for Research and Advancement in Higher Education Kyushu University
744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
2PRESTO, Japan Science and Technology Agency, Sanbancho, Tokyo 102-0075, Japan
九州大学システム情報科学府1, 高等教育開発推進センター2, 〒819-0395 福岡市西区元岡744
3JSTさきがけ〒102-0075 東京都千代田区三番町52

We have succeeded in deposition of highly stable a-Si:H films at a rate of 3 nm/s. To evaluate theirperformance as an I layer of PIN solar cells, Fill Factor (FF) of N-type c-Si/a-Si:H/Ni Schottky cells withcluster free a-Si:H films were measured. High quality stable a-Si:H films, were deposited with amulti-hollow discharge plasma CVD reactor together with a cluster-eliminating filter. Initial FF of the cellis 0.521, whereas stabilized FF is 0.495 that is 4.99% lower than the initial FF. Our multi-hollow discharge
plasma CVD method is useful to fabricate highly stable a-Si:H solar cells.

1. Introduction
Hydrogenated amorphous Silicon (a-Si:H)
suffers from the Staebler-Wronski effect, which
results in the efficiency of devices utilizing
amorphous silicon dropping as the cell is exposed
to light. Recently, we have succeeded indeposition of highly stable a-Si:H films of
4.7x1015 cm-3 in stabilized defect density at a rateof 3 nm/s at Ts= 250oC by suppressing
incorporation of amorphous silicon nanoparticles(clusters) below 10 nm in size into the films [1].
To evaluate their performance as an I layer of
PIN solar cells, Fill Factor (FF) of N-type
c-Si/a-Si:H/Ni Schottky cells with cluster freea-Si:H films was measured in this study.
2. Experimental
Cluster free a-Si:H films were deposited by amulti-hollow discharge plasma CVD method. For
the method, clusters, which are generated in thedischarge region, were driven toward thedownstream region by gas flow, because the gas
flow velocity of 330cm/s in the discharge region
was much faster than the diffusion velocity ofclusters. Therefore, cluster-free a-Si:H films weredeposited on a N-type c-Si substrate of 20x20 mm2
in the upstream region [2]. Gas of SiH4 wassupplied at a flow rate of 15 sccm. The totalpressure was 0.5 Torr. Discharge frequency andFig. 1. Schematic of multi-hollow discharge plasma
CVD reactor.

power were 60 MHz and 20 W. Under thesecondition, a-Si:H films with 1m thickness weredeposited at Ts= 250oC.
A cluster-eliminating filter was a device thatremoved clusters and through which SiH3 radicals,
which were the main precursor radicals of a-Si:H
films of device quality, were passed. The filter
reduced the contribution of the clusters todeposition of films using the difference between thesticking probability of the clusters and the surface
reaction probability of the radicals. Cluster removal
in the filter was realized by collision andattachment to the surface of the filter plates. Thefilter was composed of two stainless-steel plates of
0.1 mm in thickness with 8 or 9 slits of 1 mm inwidth. The slits of one plate were covered by theReferences[1] W. M. Nakamura, H. Matsuzaki, H. Sato, Y.
Kawashima, K. Koga, and M. Shiratani: Suf. Coat.
Technol., 205 (2010) S241.
[2] K. Koga, T. Inoue, K. Bando, S. Iwashita, M.
Shiratani, and Y. Watanabe: Jpn. J. Appl. Phys., 44(2005) L1430.
[3] Kazunori Koga, Naoto Kaguchi, Kouki Bando,
Masaharu Shiratani, and Yukio Watanabe: Review ofSci. Instr., 76 (2005) 113501.
[4] Satoshi Shimizu, Michio Kondo, and Akihisa
Matsuda: J. Appl. Phys., 97 (2005) 033522.
30.6
Initial
LS 6h40m
LS 13h20m

J (mA/cm2)

2.5

Fig. 2. Schematic of cluster-eliminating filter

3. Results
Figure 3 shows initial and stabilized J-Vcharacteristics of the Schottky cell. Initial FF of thecell was 0.521. JSC and VOC were 2.70mA/cm2 and0.35V, respectively. Stabilized FF was 0.495 which
was 4.99% lower than the initial FF. JSC and VOC
were stabilized as 2.71mA/cm2 and 0.35V,
respectively. A-Si:H films of 7% degradation wasalso realized using a triode discharge system at low
deposition rate of 0.018nm/s [4]. The deposition
rate in this work was 0.065nm/s. These results showthat our cluster free a-Si:H films at a higher
deposition rate show better stability against light
exposure. Our method is useful to fabricate highly

stable a-Si:H solar cells.
4. Conclusions
We deposited a-Si:H films using SiH4
multi-hollow discharge plasma CVD together withcluster-eliminating filter. Initial FF of the cell was0.521. Stabilized FF was 0.495 which was 4.99%
lower than the initial FF. Our method is useful tofabricate highly stable a-Si:H solar cells.
Acknowledgments
This work was partly supported by the New
Energy and Industrial Technology Development
Organization (NEDO) and Photovoltaic Power
Generation Technology Research Association(PVTEC)

Initial
LS 6h40m
LS 13h20m

20.5
0.4

1.5

0.3

10.2

0.5

0.1

000.1

0.20.30.4P (mW/cm2)

other plate as shown in Fig. 2. The transmittance of
these plates is 0.4. These plates were placed at adistance of 0.5 mm. The distance from
Cluster-eliminating filter to electrode was 6.0mm.
Cluster-eliminating filter was placed at distance of5.0mm from discharge.

00.5

V (V)
Fig. 3. Initial and stabilized J-V characteristics
of Schottky cell.
Table I. Initial and stabilized characteristics ofSchottky cell.

FF
Jsc (mA/cm2)
Voc (V)
Pmax (mW/cm2)
Rsh (Ohm cm2)
Rs (Ohm cm2)

Initial Stabilized
0.521
0.495
2.70
2.71
0.35
0.35
0.493
0.471
671
561
2931