1997 Fiscal Year Final Research Report Summary
Experimental Study of Photochemical Deposition in a Condensed Phase on a Cryogenic Substrate
| Project/Area Number |
07555041
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
機械工作・生産工学
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| Research Institution | Osaka University |
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Principal Investigator |
ENDO Katsuyoshi Osaka Univ., Grad.School of Eng., Associate Professor, 工学部, 助教授 (90152008)
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| Co-Investigator(Kenkyū-buntansha) |
OSHIKANE Yasushi Osaka Univ., Grad.School of Eng., Research Associate, 工学部, 助手 (40263206)
KATAOKA Toshihiko Osaka Univ., Grad.School of Eng., Professor, 工学部, 教授 (50029328)
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| Project Period (FY) |
1995 – 1997
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| Keywords | photochemical reaction / deposition / condensed phase / cryogenic substrate / excimer laser / silane / crystalline silicon / two-photon absorption |
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| Research Abstract |
We have studied photochemical deposition in a condensed phase. In the experiment, liquid silane (SiH_4) on a cryogenic substrate is irradiated with KrF and ArF excimer laser. The deposition film is characterized by Raman scattering, scanning electron microscopy, transmission electron microscopy and transmission electron diffraction. The film is composed of many rod-like crystalline silicon (c-Si) products. Their diameter and height are 400-500 nm and 500-700 nm, respectively. It is remarkable that the rod-like c-Si has grown on the cryogenic substrate. Therefore, we consider that the liquid-solid interface reaction plays an important role in the crystallization growth. In other words, the growth from the c-Si surface is necessary or crystallization. We propose the following deposition mechanism. Namely, (1) SiH_4 molecule photoexcited by a two-photon absorption would be dissociated into a SiH_3 radical and an atomic hydrogen. (2) A created atomic hydrogen extracts a hydrogen atom from the "neighboring" molecule, and forms a hydrogen molecule H_3. (3) The remaining radicals combine and form a Si-Si bond. A similar reaction occurs successively and the generated hydrogen silicides (Si_xH_y) are deposited on the substrate. In the second stage, the formed nuclei (Si_xH_y) grow to be c-Si through the one-photon absorption. Generally speaking, as a molecule becomes larger, its absorption edge shifts to longer wavelength. Therefore, the large hydrogen silicides are excited and react easily with "neighboring" SiH_4 through the one-photon absorption process. This technique solves general problems in photochemical vapor deposition techniques, such as deposition on the optical window, thermal damages of the substrate and the low deposition rate in the gas phase.
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