22P020-O
Bias Dependent Reactions of a Si(110) Substrateon Irradiation of Hydrogen Plasma
水素プラズマ照射によるシリコン(110)基板相互反応のバイアス依存性
Y. Takami1, K. Hara2, Y. Takaki1, M. Shinohara1, Y. Matsuda1 and H. Fujiyama1
高見佳生 1，原 幸治郎 2，高木雄也 1，篠原正典 1，松田良信 1，藤山 寛 1
Graduate School of Engineering. Nagasaki Univ. 1, Graduate School of Sci. and Technol. 2
長崎大学大学院工学研究科 1，長崎大学大学院生産科学研究科 2,It has been investigated hydrogen exposure process on Si(110) surface, with infrared absorption
spectroscopy in multiple internal reflection geometry (MIR-IRAS). Infrared absorption spectra showedthat inserting hydrogen in Si(110) result in the formation of amorphous layer. The kinds of the generated
hydride components were changed with the exposure. The SiH was formed in the initial stage and theSiH2 was formed in the latter stage.

1. Introduction
Silicon is indispensable in semiconducting
materials and is used for a solar cell, LSI and so on.
Hydrogen plasma is well known to modify themorphology, structure and properties of siliconmaterials. The interaction of hydrogen with c-Si
surfaces gives rise to a large variety of phenomena,such as etching, vacancy-generation and so on. It isconsidered that the interaction is affected to several
factors like substrate bias and temperature.
Nevertheless, it is not fully understood howhydrogen plasma-induced reactions on Si crystal
surfaces. In order to know the details of theplasma-surface interaction, we need to understandhow hydrogen is inserted in Si surface and bulk Si.
In this study, therefore, we used in situ and real time
infrared reflection absorption spectroscopy (IRAS)
in multiple internal reflection (MIR) geometry toinvestigate the interaction of hydrogen plasma andSi(110) surface with substrate bias.
2. Experiment
The system that we used in this study was achamber equipped with an MIR-IRAS monitoring
system, an inductively coupled plasma (ICP) source,
and a gas delivery system, as is schematicallyillustrated in Fig.1. The Si prism used here wasmade of n-type Si(110) wafers. The prisms had adimension of 0.5 × 10 × 40 mm, withmirror-polished 45° bevels on each of the shortedges. RF plasma was generated by applying
13.56MHz RF power to a coil wrapped around aglass tube. Hydrogen plasma was generated byusing 30W RF power at a hydrogen pressure of50mtorr. The RF bias during plasma exposure wasgiven by the high-frequency power source of 800
KHz. The silicon surface covered with a chemicaloxide layer was used as the reference spectrum of
all spectra in order to recognize the changed portion.
The chemical oxide layer was produced in a boiled
H2O2/H2SO4 solution.

Fig.1

Experimental set up

3. Experimental results and discussion
Figure 2 shows infrared absorption spectra ofSi(110) exposed hydrogen plasma with substratebias, -200V. Each figure indicated the exposure
time. These spectra showed that the peak intensity
was increased with the exposure times, indicatingthat the hydride components were generated by thehydrogen plasma exposure. The peak located at

22P020-O
2030cm-1 was observed at low exposure reagion.
The peak at 2100cm-1 was observed at the highexposure region. The peak position was changed
with the plasma exposure. It means that the kinds ofhydride components were changed with thehydrogen exposure. According to the previousreports, the peak at 2030cm-1 is assigned to amonohidride (SiH) component in amorphous siliconphase, that at 2100cm-1 is assigned to silicondihidride (SiH2) component in amorphous siliconphase. Then we can consider as follows: the silicon
cyrstal was changed to amorphous layer to form
SiH components in the Si by hydrogen plasma
exposure with the substrate bias of -200V. The SiH
components
werehydrogenatedtoSiH2components by further exposure to the hydrogenplasma.
Figure 3 shows infrared absorption spectra ofSi(110) exposed hydrogen plasma with substratebias, which is respectively -50V, -100V, -150V and-200V. Because peak intensity is strong withincreasing bias, hydrogen is easily introduced inSi(110) with substrate bias. In case of Si(110)applying substrate bias -50V and none, the reactionof Si(110) surface is the main, as the main peak isSiH. In case of -100V, -150V and -200V, the main
peak is bulk-SiH2. Therefore, the main reaction isthe amorphous form.
4. Conclusion
We investigated the interaction of hydrogenplasma with Si(110), especially the effect of theapplied substrate bias with infrared spectroscopy inmultiple internal reflection geometry (MIR-IRAS).
Infrared absorption spectra showed that insertinghydrogen in Si(110) result in the formation ofamorphous layer. The kinds of the generated
hydride components were changed with theexposure. The SiH was formed in the initial stage
and the SiH2 was formed in the latter stage.

Fig.2 Infrared spectra of Si(110) surface exposed
to hydrogen plasma with the substrate bias of-200V.

Fig.3 Infrared spectra of Si(110) surface exposed
to hydrogen plasma with the substrate bias offloating, -50V, -100V, and -200V.

Acknowledgments
This research was partly supported by both of a
Grant-in-Aid for Young Scientists (A), No.
20684027 (2008-2012) and a Grand-in-Aid for
Scientific Research on innovative Areas No.
22110511 (2010-2012) from the Ministry of
Education, Culture, Sports, Science and Technology(MEXT) of Japan.