Study The Pattern and Thickness Effect on Low- Temperature Polycrystalline Silicon Thin Film Induced by Nickel Silicide Crystallization Method
| Autor: | Tza-Hao Wang, 王澤豪 |
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| Rok vydání: | 2001 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 89 Low-temperature polycrystalline silicon (poly-Si) thin film has been widely studied. Among various approaches, the most useful method to mediate crystallization is metal induced crystallization (MIC) or metal induced lateral crystallization (MILC). In the MIC or MILC process, Ni is deposited on amorphous silicon (a-Si). Consequently, NiSi2 forms upon annealing. As the NiSi2 moves further towards the a-Si region, poly-crystalline Si forms behind the NiSi2 front. It is known that the quality of crystallinity of poly-Si thin film will deeply affect the electrical properties of the transistor. How to get a good quality poly-Si via low-temperature process is important. It is shown that both the deposited Ni pattern and the thickness of a-Si layer significantly affect the crystallization rate, crystallinity and the residual Ni impurities in the poly-Si thin film. In this work, these effects will be discussed and a model will be proposed to explain them. In the first section, we will discuss the geometrical effect of the Ni pattern on the quality of crystallization silicon. From optical microscopy (OM) images, we find that a-Si covered with patterned Ni whose pattern curvature is smaller would exhibit a high crystallization velocity. In contrast, a pattern having a larger curvature leads to a smaller crystallization velocity. Transmission electron microscopy (TEM) and Raman spectroscopy indicate that the crystallinity of MILC of a-Si covered with a rectangular layer of Ni is better than that covered with a circular layer of Ni. From SIMS analysis, the residual Ni concentration in MILC of a-Si covered with Ni rectangles is smaller when compared to that of a-Si covered with Ni circles. In the second section, the effect of a-Si layer thickness will be discussed. From the OM images, the MILC crystallization rate increases with the thickness of a-Si. X-ray Diffractometer (XRD), TEM and Raman spectroscopy, show that the grain size of crystal silicon of thicker a-Si is larger with better crystallinity. SIMS analysis indicates that the residual Ni concentration in the MILC layer is smaller in 1000Å a-Si case than that in the 300 Å a-Si layer. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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