JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

4-06
Atomistic Study of Irradiation-induced Mass
Transport Process
Y. Ikoma a) , T. Motooka a) , H. Sakita a) , Hafizal Yahaya a) ,
H. Naramoto b) , K. Narumi b) , S. Sakai b) b, c)
and Y. Maeda
a) Department of Materials Science and Engineering, Kyushu University,
b) Advanced Science Research Center, JAEA, c) Faculty of Engineering, Kyoto University
A nanometer-sized pores (nanopores) is of great interest
for a possible application to molecular sensors such as DNA
sequencers 1) . These nanopores are fabricated using
biomaterials and insulators. Especially, insulator
nanopores are mainly fabricated by means of ion beam
2, 3) 4)
sculpting or electron beam exposure . We have
investigated the nanopore formations utilizing the structural
change in Si and by ion irradiation 5, 6) and smart cut process
by hydrogen ion implantation into nanopore-formed
Silicon-on-Insulator (SOI) substrates 7) .
In the case of the ion irradiation technique, SOI(100)
substrates with the top Si layer of 180 nm. The initial
m-size holes were prepared by ~30 keV Ga + focused ion
beam irradiation using HITACHI FB-2000 at Kyushu
University. Then the B + , Si + , P + , and Ar + ions with the
energy of 10 keV were implanted into the hole region at
room temperature with doses of 4.4 × 1016 /cm 2 , 4.3 ×
10 16 /cm 2 , 0.9 × 1016 /cm 2 , and 1.5 × 1016 /cm 2 , respectively.
These implantations were carried out by 400 kV ion
implanter at TIARA. In order to avoid possible carbon
contaminations on the sample surfaces, the irradiation
chamber was kept cooled by surrounding cold shrouds.
Figure 1 shows the transmission electron microscopy
(TEM) photographs obtained from the SOI samples before
and after P + ion irradiation. The structural changes induced
by ion bombardments were analyzed based on the dark-field
(DF) and bright-field (BF) images combined with the
selected-area diffraction (SAD) patterns. The dark-field
images indicate that the hole region is crystalline before ion
irradiation, but the hole region is changed to amorphous
after ion irradiation. The pore area before and after ion
irradiations is changed from 4.73 m 2 to 4.56 m 2 ,
respectively. The shrinks of B + , Si + , P + , and Ar + ions per
dose are 0.5 × 10-25 cm 4 , 1.8 × 10-25 cm 4 , 1.9 × 10-25 cm 4 , and
5.5 × 10-25 cm 4 , respectively. It is found that the shrinkage
effects can be attributed to dilation of crystalline Si upon
amorphization induced by ion beam bombardments. The
observed difference in ion species may be due to the
difference in the number of the ion-beam-induced
Fig. 1 TEM photographs from the SOI sample with a hole
before and after the irradiation with 10 keV P + ions.
JAEA-Review 2010-065
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Frenkel-pairs, which is consistent with the D-D pair model
for ion-beam-induced amorphization of Si proposed
previously 8, 9) .
We also investigated the smart cut process by hydrogen
ion implantation into nanopore-formed SOI substrates.
The nanopore samples were fabricated by a pulse jet CVD
10)
technique described elsewhere . Separation by Implanted
Oxygen (SIMOX) (100) with SOI and buried oxide (BOX)
layers of 180 nm and 100 nm, respectively, were cleaned by
the conventional RCA method 11) . These substrates were
introduced into the chamber after being dipped in aqueous
5% buffered HF in order to remove surface oxides.
Electronic grade CH 3SiH 3 was introduced into the growth
chamber using a supersonic pulse valve with a nozzle
diameter of 0.8 mm. The pulse width and frequency were
set at 100 µs and 10 Hz, respectively. The substrate
temperature was set at 850 °C. After forming the SiC
heteroepitaxial layer and the {111} faceted pits on SOI layer,
these samples were dipped into 5% buffered HF solution for
10 min in order to remove the BOX layer under the pits.
Hydrogen ion implantation was performed at room
temperature with 1.44 MeV H 2 + up to the dose of 1 ×
10 17 H/cm 2 utilizing 3 MV single-ended accelerator at TIARA.
In order to separate the nanopore-grown film from SIMOX
substrates, we heated the as-implanted sample at ~500 °C in
air. From the scanning electron microscopy observation, it
was confirmed that the sample surface was successfully cut
with the depth at 10m from the substrate surface.
These results suggest that ion beam irradiation is
promising not only for inducing the structural changes of
solids but also for fabricating nanopore systems by the
smart-cut technique.
References
1) M. Rhee and M. A. Burns, Trends Biotechnol. 24 (2006)
580.
2) J. Li et al., Nature 412 (2001) 166.
3) J. Li et al., Nature Mater. 2 (2003) 611.
4) A. J. Storm et al., Nature Mater. 2 (2003) 537.
5) T. Motooka et al., JAEA Takasaki Ann. Rep. 2006
(2008) 169.
6) T. Motooka et al., JAEA Takasaki Ann. Rep. 2007
(2008) 140.
7) Y. Ikoma et al., Abst. 4th Takasaki adv. Radiat. Res.
Symp. (2009) 170.
8) T. Motooka, Phys. Rev. B 49 (1994) 16367.
9) T. Motooka et al., Phys. Rev. Lett. 78 (1997) 2980.
10) Y. Ikoma et al., Proc. SPIE 6984 (2008) 69841V.
11) W. Kern and D. A. Puotinen, RCA Rev. 31 (1970) 187.