Effects of oxygen on crystallization of amorphous silicon films and polysilicon TFT characteristics |
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Authors: | Yong-Min Ha Seong-Hoon Lee Chul-Hi Han Choong-Ki Kim |
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Affiliation: | (1) Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong-Dong, Yusong-Gu, 305-701 Taejon, Korea;(2) Gold Star Co, Seoul, Korea |
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Abstract: | Oxygen ions were implanted into the amorphous silicon film deposited at 540°C in order to study the effects of oxygen on the
solid phase crystallization of silicon films. The resulting films were investigated using transmission electron microscopy,
x-ray diffraction (XRD), and also by measuring the electrical characteristics of polycrystalline silicon thin film transistors
(TFTs) fabricated in the crystallized films. The development of {111} texture as a function of annealing time is similar to
films implanted with Si, with higher oxygen samples showing more texture. Transmission electron microscopy shows that the
grain size of completely crystallized films varies little with oxygen concentration. The electrical performances of TFTs are
found to degrade with increasing oxygen dose. The trap state density increases from 5.6 × 1012/cm2 to 9.5 × 1012/cm2 with increasing oxygen dose. It is concluded that for a high performance TFT, oxygen incorporation in the Si film should
be kept to 1019/cm3 or less. |
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Keywords: | Implantation oxygen polysilicon TFT solid phase crystallization trap state density |
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