Effects of high pressure annealing on the characteristics of solid phase crystallization poly-Si thin-film transistors

• Published in: Journal of applied physics 2008-02, Vol.103 (4), p.044508-044508-5
• Main Authors: Kim, Moojin, Kim, Kyoung-Bo, Lee, Ki-Yong, Yu, CheolHo, Kim, Hye-Dong, Chung, Ho-Kyoon
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2885345

Integrating circuits into organic light emitting diode displays require fabrication of polycrystalline silicon (poly-Si) based thin-film transistors (TFTs) on glass substrates. In this work we evaluated the use of high pressure annealing (HPA) process of poly-Si films in H 2 O atmosphere to improve TFT characteristics via reducing defect density in poly-Si films. We attempted to develop a HPA process at temperatures below 600 ° C without causing any glass distortion and reducing the throughput. The HPA-treated poly-Si film was analyzed using various spectroscopic methods such as Raman, x-ray photoelectron spectroscopy, and transmission electron microscope, and the evaluation of the characteristics of TFTs fabricated by such poly-Si films was made. The heating at 550 ° C with 1 MPa H 2 O vapor increased the carrier mobility from 8.5 to 20 cm 2 ∕ V s and reduced the absolute value of the threshold voltage from 9.6 to 6.5 V , as compared with the conventional solid phase crystallization (SPC) process. The sub-threshold swings also decreased from 1.2 to 0.8 V /decade. Since the realization of good performance in poly-Si depends on the defect density, the poly-Si formed by a combined process of SPC and HPA may be well suited for fabrication of poly-Si TFTs for flat panel displays such as liquid crystal display and active matrix organic light emitting diode that require circuit integration on panels.