Large-Grain Doped Poly-Si Films Fabricated Using New Excimer Laser Annealing Technique
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LARGE-GRAIN DOPED POLY-SI FILMS FABRICATED USING NEW EXCIMER LASER ANNEALING TECHNIQUE Hiroshi Iwata, Tomoyuki Nohda, Satoshi Ishida, Takashi Kuwahara, Keiichi Sano, Hiroyuki Kuriyama*, Shigeru Noguchi, Hiroshi Hanafusa, Keiichi Kiyama*, Shinya Tsuda, Shoichi Nakano and Yukinori Kuwano SANYO Electric Co., Ltd. 1-18-13 Hashiridani, Hirakata, Osaka 573, Japan * also with Giant Electronics Technology Co., Ltd. 1-6-5 Higashinihonbashi, Chuo-ku, Tokyo 103, Japan
ABSTRACT The grain size of phosphorous (P)-doped poly-Si film has been enlarged to about 5000 A by controlling the solidification velocity of molten Si during ArF excimer laser annealing. The drastically enlarged grain has few defects inside the grain. It has been confirmed that control of the solidification velocity is effective for P-doped poly-Si similar to the case of nondoped poly-Si films. In addition, a sheet resistance of 80 fl/El ( p =4X 10-4 fl2 cm) has been achieved for very thin (500 A) films by recrystallizing PECVD P-doped a-Si films.
INTRODUCTION Recrystallization methods for poly-Si films have attracted wide attention in the field of large-area electronics, especially for liquid crystal displays (LCDs). Of the various approaches available, solid phase crystallization realized very large grain poly-Si films[l]. However, this fabrication method requires a high-temperature process (>600 tC) and a very long annealing time. On the other hand, excimer laser annealing is a very promising technique for fabricating poly-Si TFTs on glass substrates because the absorption coefficient of a-Si is quite large for the UV light of the excimer laser. A rather serious problem, however, is that poly-Si films obtained by this technique have a grain size of less than 1000 A[2],[3]. This is because the solidification velocity during excimer laser annealing is extremely high and the melting duration is in the order of nano seconds[4]. Therefore, in order to enlarge the grain size, we started on the control of the solidification velocity of molten Si in a low-temperature (-400 'C) substrate heating process during excimer laser annealing. We made both numerical simulation and experimental investigation. It was found that for non-doped poly-Si films, it is possible to achieve a drastic enlargement of grain size. High field effect mobility, high uniform TFT were achieved by this method. This paper reports on a method developed to control the solidification velocity for P-doped poly-Si films. The target of the study is the realization of low-resistivity, thin P-doped poly-Si films with a sheet resistance of less than 100f2/[l fabricated in a low-temperature process. Applications of the thin P-doped poly-Si films are expected in the source-drain region of high performance poly-Si TFTs and in wiring and electrode materials.
Mat. Res. Soc. Symp. Proc. Vol. 283. 01993 Materials Research Society
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LARGE-GRAIN NON-DOPED POLY-SI FILMS
Excimer laser beam We used thermal analysis X a-Si X y*to calculate the recrystallization process for non-doped poly-Si Z -4-Si0 2 Glass fi
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