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Influence of different gas environments on the formation of thin film polysilicon by excimer laser annealing

W. C. CHANG1, K. F. YARN2, W. J. LUO3,* , C. T. CHENG2, W. C. CHUANG4, C. F. LO1

Affiliation

  1. Department of Electronic Engineering, Southern Taiwan University, Tainan County 710, Taiwan
  2. Department of Electronic Engineering, Far East University, Hsin-Shih, Tainan County 744, Taiwan
  3. Department of Refrigeration, Air Conditioning and Energy Engineering, National Chin-Yi University of Technology, Taichung County 411, Taiwan
  4. Department of Electro-Optics Engineering, National Formosa University, Huwei, Yulin, Taiwan, ROC

Abstract

Excimer laser annealing (ELA) amorphous silicon (a:Si) to poly-silicon (poly-Si) in different gas environments, i.e. N2 or N2 mixed with O2:2%, for the fabrication of thin film transistors (TFTs) is studied. Influence of laser power on the surface morphology, grain size and height of gibbous grain is also investigated. The variations of threshold laser power for the generation of surface ablation in pure N2 only and the mixture of N2:98% and O2:2% environments are also discussed respectively. From experiment, it is found the combination of N2:98% and O2:2% can enhance the threshold laser power for the generation of surface ablation from 320mJ/cm2 to 390 mJ/cm2 . In the condition of average grain over 0.25 μm, the process window (i.e. laser power for processing ability) is 30mJ/cm2 for pure N2 only, but is 50mJ/cm2 for the combination of N2:98% and O2:2%.

Keywords

Excimer laser annealing (ELA), Amorphous silicon, Surface ablation, Grain.

Citation

W. C. CHANG, K. F. YARN, W. J. LUO, C. T. CHENG, W. C. CHUANG, C. F. LO, Influence of different gas environments on the formation of thin film polysilicon by excimer laser annealing, Optoelectronics and Advanced Materials - Rapid Communications, 2, 11, November 2008, pp.697-700 (2008).

Submitted at: Sept. 2, 2008

Accepted at: Oct. 30, 2008