Properties of Large Grain-Size poly-Si Films by Catalytic Chemical Sputtering
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PROPERTIES OF LARGE GRAIN-SIZE POLY-Si FILMS BY CATALYTIC CHEMICAL SPUTTERING Atsushi Masuda, Koji Kamesaki, Akira Izumi and Hideki Matsumura School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Tatsunokuchi, Ishikawa 923-1292, JAPAN ABSTRACT Large grain-size polycrystalline Si (poly-Si) films are obtained on glass substrate by newly developed catalytic chemical sputtering method at low temperatures around 400 C. Si films are also epitaxially grown on (100) single-crystalline Si substrates. In the method Si films are deposited by the chemical transport of SiH4 species generated by the reaction between solid Si target and catalytically generated H atoms. Efficient deposition is realized using the remarkable difference in the etch rate depending on Si target temperatures. That is, SiH4 species are efficiently generated on cooled Si target by atomic-H etching and deposited on substrates with suppressed etching phenomena by heating. Full-width at half maximum of transverse-optical Raman signals originating from crystalline phase for the obtained poly-Si films is narrower than that for poly-Si prepared by excimer-laser annealing. It was noticeable that the grain size exceeds 1 m for the films with a thickness of about 1 m. Growth mode of poly-Si films especially in the initial stage is remarkably changed with a difference in the substrate material. It was found that formation of seed layer enhances the growth of poly-Si films on glass substrate. INTRODUCTION Device-quality hydrogenated amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) films are obtained at low temperatures around 400 C by plasma-enhanced chemical vapor deposition (PECVD) or catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD, using silane (SiH4). a-Si:H or poly-Si films are also obtained utilizing even chemical transport of volatile silicon-hydride species generated by the reaction between a solid silicon (Si) and hydrogen (H) atoms produced by plasma decomposition of hydrogen (H2) molecules [1,2]. Recently, it was found that the efficiency of gas use for Cat-CVD is much higher than that for PECVD, for example, about 60-80 % for a-Si:H deposition [3]. It has been also confirmed by laser-induced fluorescence and ultraviolet absorption that H atoms are also effectively generated from H2 molecules by catalytic cracking reaction and that the density of H atoms in the gas phase generated by it is one or two orders of magnitude higher than that for plasma decomposition of H2 molecules in similar conditions [4]. It is also expected that no ion bombardment occurs for the chemical transport using H atoms generated by catalytic cracking reaction. Thus, the authors have been developed a novel thin-film deposition method using the reaction between Si target and H atoms generated by the catalytic
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cracking reaction instead of plasma decomposition [5,6]. Although this phenomenon is not physical sputtering but chemical etching, they named the method "catalytic chemical sputtering", from a
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