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PROPERTIES AND PRODUCTION MECHANISM OF LOW-TEMPERATURE DEPOSITED CAT-CVD POLY-SILICON FILMS HIDEKI MATSUMURA*, YOICHI HOSODA** and SEIJIRO FURUKAWA** *Japan Advanced Institute of Science and Technology (JAIST) Hokuriku, Tatsunokuchi, Ishikawa-ken 923-12, Japan **Tokyo Institute of Technology, Department of Applied Electronics, Nagatsuda, Midori-ku, Yokohama 227, Japan ABSTRACT Poly-silicon films are obtained at temperatures as low as 400 °C by the catalytic chemical vapor deposition (cat-CVD) method, in which deposition gases are decomposed by the catalytic or pyrolytic reactions with a heated catalyzer near substrates. It is found that there are roughly two modes of deposition conditions such as low gas pressure mode and high gas pressure mode for obtaining poly-silicon films, and also that the Hall mobility of the cat-CVD poky-silicon films of low gas pressure mode sometimes exceeds over 100 cm /Vs. 1.INTRODUCTION A poly-silicon (poly-Si) film on a glass substrate is one of promising materials for thin film transistors (TFT) used in a liquid crystal display (LCD) panel. Such poly-Si films are mainly prepared by the conventional thermal CVD at around 600 0 C or by the laser spot annealing [1,2]. However, the process temperature in the conventional CVD appears too high to suppress the thermal distortion of the glass substrate. It is believed that the temperature should be kept lower than 450 0 C at least for the fabrication of a wide area LCD panel, because of this glass distortion. Additionally, the laser annealing is not suitable for wide-area polycrystallization. Thus, the development of a new technology, which can prepare wide-area poly-Si films at lower than 450 *C, is strongly required. We have developed a new deposition method named "catalytic chemical vapor depostion (cat-CVD) method" [3]. In the method, deposition gases are decomposed by the catalytic or pyrolytic reactions with a heated catalyzer placed near substrates, and so that, the films are deposited at low temperatures without help from plasma or photochemical excitation. Actually, one of authors has already found that the poly-Si films can be often obtained at lower than 400 0 C by the cat-CVD method, when the gas pressure during deposition Pg and the temperature of catalyzer Ta are maintained within a certain range [4]. Since then, we continue the s uy on this low-temperature poly-Si formation, in order to obtain higher mobility films. This paper is to describe the results of such further studies. It is found that there are roughly two modes of deposition conditions to obtain poly-Si films at low temperatures. One is the condition of relatively low Tctt around 1300 °C (lower than melting temperature of silicon) with re tively high Pg around 0.1 Torr, and the other is that of high Tcat over 1600 °C (higher than silicon melting temperature) with low Pg around 0.001 Torr. And it is found that the Hall mobility of poly-Si films deposited with such low Pg conditions sometimes exceeds over 100 cm2 /Vs. 2.FUNDAMENTALS FOR POLY-SILICON FORMATION The depo