22P021-O
Substrate Temperature Effect in the Interactionof Hydrogen Plasma with a Silicon Surface
水素プラズマ-シリコン基板表面相互作用の温度依存性
Kojiro Hara1, Yoshiki Takami2, Yuya Takaki2,Masanori Shinohara2, Yoshinobu Matsuda2, Hiroshi Fujiyama2
原 幸治郎 1，高見佳生 2，高木雄也 2，篠原正典 2，松田良信 2，藤山 寛 2
1Graduate School of Science and Technology, Nagasaki University
1-14 Bunkyo, Nagasaki 852-8521, Japan
2
Graduate School of Engineering, Nagasaki University
1-14 Bunkyo, Nagasaki 852-8521, Japan
1 長崎大学生産科学研究科，2 長崎大学工学研究科

We investigated hydrogen insertion process into silicon crystal from silicon surface, with infraredabsorption spectroscopy in multiple internal reflection geometry (MIR-IRAS). Infrared spectra suggested
that kinds of generated silicon hydride components were changed with the substrate temperature. The
formation of amorphous SiH components was increased with the substrate temperature; on the other hand,the formation of amorphous SiH2 components was decreased on the contrary to the substrate temperature.
1. Introduction
Silicon (Si) is an important semiconductormaterial used for electronic devices such as LSI,
solar cells and so on. Reaction of silicon withplasma is one of the important processes in Si
device processing. Hydrogen plasma is one of theimportant plasmas, because the hydrogen radicals
and ions generated in hydrogen plasma play animportant role in either etching or deposition
processes. Then, to control preciously either process,it is important to investigate an interaction ofhydrogen plasma with Si surface. A lot of works
have been so far reported, but the interaction has
not been cleared. One of the problems is to know
the interaction process. The comprehension of theprocess tells us how to control the process.
However, the process is hard to be investigated,because the surface is subjective to oxidation. At
least “in-situ” measurement has to be required.
Then, we use infrared spectroscopy in multiple
internal reflection geometry (MIR-IRAS) to
investigate it. The interaction depends on various
factors, such as substrate bias, substratetemperature, and so on. In this study, we focus on
the substrate temperature effect on the interaction
between Si crystal and hydrogen plasma. We haveinvestigated the interaction of Si(100) and Si(110)
surfaces with hydrogen plasma. In this paper wepresent about the interaction on Si(110) surface.
2. Experiments
The chamber used in this study was equippedwith RF plasma source, high vacuum pump system,and IRAS monitoring system. The pressure wasevacuated to 1×10-6 Torr. RF plasma was generated
by applying 13.56 MHz RF power to a coilwrapped around a glass tube. Hydrogen plasma wasgenerated using 30W RF power at a hydrogenpressure of 50 mTorr. The substrate temperature iscontrolled by heater. The Si prisms were used as asubstrate. The prisms were made of n-type Si (110)wafers with the resistivity of approximately 10cm.
The prisms had a dimension of 0.5 × 10 × 40 mm,
with mirror-polished 45° bevels on each of the short

Fig.1 Experimental set up

edges. As the reference spectrum, the surface ofsilicon covered with a chemical oxide layer wasused. The chemical oxide layer was produced in aboiled H2O2/H2SO4 solution.
3. Results and Discussions
Figure 3 shows the infrared absorption
spectrum of Si(110) exposed to hydrogen plasma
with substrate temperature from 70 to 200 °C. Thepeak at approximately 2070 cm-1 and the peak atapproximately 2090cm-1 can be assigned toSiH-SiH chains of Si(110) surface. The peak at
approximately 2140 cm-1 can be assigend to theSiH2 on the step of Si(110) surface. The surfaces
should become atomically random with thehydrogen plasma exposure, since the observed
peaks in this region were broad. The amorphous
SiH2 had a peak at approximately 2100cm-1. Thesecomponents were overlapped with the surface
silicon hydride components. The peak became
sharp with the substrate temperatures. It means thatthe amorphous SiH2 compoinets was suppressedwith the substrate temperatures. The peak at 2000
cm-1 was also observed. The peak can be assigned
to SiH component observed in amorphous phase.
The peak was increased with the substratetemperature. The amount of the SiH components inamorphous phase were increased with the substratetemperature. These results indicated that theformation of amorphous SiH2 components wassupressed with the substrate temperature, and thatthe formation of amorphous SiH components wasincreased with the substrate temperature.

chaneged with the substrate temperature. The
formation of amorphous SiH components wasincreased with the substrate temperature; on theother hand, the formation of amorphous SiH2components was decreased on the contrary to thesubstrate temperature.

4. Conclusion
We investigated the interaction of hydrogenplasma with Si(110) surface, and its substratetemperature effect, by using infrared spectroscopy
inmultiple
internal
reflection
geometry(MIR-IRAS). Infrared spectra suggested that kindsof generated silicon hydride comoponents wereAcknowledgments
This research was partly supported by both of a
Grant-in-Aid for Young Scientists (A), No.
20684027 (2008-2012) and a Grant-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.

Fig.3 Infrared spectra(from 70 to 200 °C)