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Recent Progress of Low Temperature Poly Si Tft Technology

  • Kiyoshi Yoneda (a1)


Since being introduced to the production line in 1996, replacing the first generation a-Si TFT line, low-temperature poly-Si production technology aimed at manufacturing small and medium size LCD products has improved steadily corresponding to customers' requirements for rapid growth of the DVC and DSC markets. In the future, this production technology must progress to actual industry technology levels in order to cope with production applied not only to large size displays, which have a major market share in the present display market, but also to a large glass substrate, which effectively cuts the cost of products, although improvement of production yield and productivity in terms of pursuing cost reduction must be proceeded.

This paper has described existing problems of inherent low-temperature poly-Si TFT processes and their relating additional processes in present production methods. We have also discussed updating production technologies. To cope with production for a large size display, it is necessary to establish fabrication technology of higher performance TFTs with electron mobility larger than 200cm2/V·s. We believe that one key technology is to fabricate a large-scale and highly-uniform recrystallized poly-Si film with smooth surface morphology as well as precisely-controlled grain size in production. To cope with production using a large glass substrate, it is essential to develop ELA equipment with laser power greater than 200W.



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1) Kuriyama, H., Kiyama, S., Noguchi, S., Kuwahara, T., Ishida, S., Nohda, T., Sano, K., Iwata, H., Kawata, H., Osumi, M., Tsuda, S., Nakano, S. and Y, Kuwano : “Enlargement of Poly-Si Film Grain Size by Excimer Laser Annealing and Its Application to High-Performance Poly-Si Thin Film Transistor”, Jpn. J. Appl. Phys., Vol. 30, pp.37003703 (1991).
2) Hayashi, H., Kunii, M., N, Suzuki, Kanaya, Y., Kuki, M., Minegishi, M., Urazono, T., Fujino, M., Noguchi, T., Yamazaki, M. : “Fabrication of Low-Temperature Bottom-Gate Poly-Si TFTs on Large-Area Substrate by Linear-Beam Excimer Laser Crystallization and Ion Doping Method”, IEDM'95 Technical Digest, pp.829832 (1995).
3) Morimoto, Y., Hirano, K., Abe, H., Kuwahara, T., Hasegawa, I., Yuda, S., Sotani, N. and Yoneda, K. : “A 2.4-in. Driver-Integrated Full-Color Quarter VGA (320×3×240) Poly-Si TFT LCD by a Novel Low Temperature Process Using a Combination of ELA and RTA Technology”, IEDM'95 Technical Digest, pp.837840 (1995).
4) Yoneda, K. : “State-of the Art Low Temperature Processed Poly-Si TFT Technology” Proc. of the 17th IDRC, pp. M4047(1997).
5) Yoneda, K. : “Current Status of Production Technologies in Low-Temperature Poly-Silicon TFTs" Proc. of IDW'97, pp. 231234(1997).
6) Yoneda, K., Segawa, Y., Yamada, T., Kihara, K., Yokoyama, R. : “A Smart Arrangement of TFTs in Low-Temperature Poly-Si Circuitry for Achieving Higher Effective Yield in” Proc. of the 17th IDRC, pp. L14 (1997).
7) Tung, Yah-Jiun, Carey, Paul G., Smith, Patrick M., Theiss, Steven D., and King, Tsu-Jae : “An Ultra Low-Temperature Fabricated Poly-Si TFT with Stacked Composite ECR-PECVD Gate Oxide”, SID'98, to be published.
8) Giust, G. K., and Sigmon, T. W. : “Sputtered Low-Temperature Laser-Crystallized Polysilicon Thin Film Transistors”, VLSI Symposium 1998, to be published.
9) Jang, Y. H., Park, W. S., Takeya, M., Jong, G. S., and Ohmi, T. :“Low-Temperature Polycrystalline Silicon Deposition by Very High Frequency Sputtering Using Ar and H2 ”, J. Electrochem. Soc., Vol. 144, pp.39733978 (1997).


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