Excimer-Laser Crystallization of Patterned Si Films At High Temperatures Via Artificially Controlled Super-Lateral Growt
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H. Jin Song and James S. Im Department of Chemical Engineering, Materials Science, and Mining Engineering, Columbia University, New York, New York 10027 ABSTRACT
Based on the artificially controlled super-lateral growth approach, we have developed a novel excimer-laser-based high-substrate-temperature method for producing singlecrystal Si islands on SiO2 . By irradiating a photolithographically preconfigured sample, complete melting of an Si film is induced only at precisely predesignated An intentionally locations within patterned and physically isolated islands. incompletely melted section within each island initiates lateral growth of crystalline grains. A "bottleneck" portion of the island permits only one of the laterally growing grains to propagate into the main portion of the island. The low nucleation-to-growthrate ratios that are attainable with high substrate temperatures (1000-1200 'C) can lead to nearly unlimited lateral growth distances; with a proper combination of the substrate 2temperature and the island dimension, the main area of an island-up to 50x50 pno in area-is readily converted into a large single-crystal region. INTRODUCTION
Polycrystalline-Si-based thin-film transistors (TFTs) on quartz substrates have been and continue to be utilized in the production of active-matrix liquid-crystal displays (AMLCDs) [1,21. This configuration (i.e., a crystalline-Si film on a quartz substrate) is particularly attractive for manufacturing small AMLCDs in that it enables direct integration of driver circuits and also permits the convenient use of high temperature device fabrication processing steps [2]. However, the microstructural integrity of currently utilized polycrystalline Si films is rather lacking as a result of the presence of a high density of high-angle grain boundaries within the material. Consequently, the device quality of TFTs that are fabricated on these materials iswithout exception-inferior to those that are built on single-crystal Si films or surfaces.
In recent years, excimer-laser crystallization (ELC) has been actively investigated mainly as a glass-substrate-compatible means for crystallizing asdeposited a-Si films [3]. The conventional ELC approaches produce small- or largerained polycrystalline Si films that contain randomly located high-angle grain Once again, as a result of such a oundaries throughout the material [4,5]. microstructure, these films do not excel in terms of permitting production of TFTs that possess high performance and uniform device characteristics [5]. In order to prepare better materials in an efficient manner, artificially controlled super-lateral growth (ACSLG) methods are being developed [6,71 in our laboratory. Derived from the super-lateral growth (SLG) phenomenon [4,8], these methods are based on inducing complete melting and incomplete melting at precisely predetermined locations, and controlling the subsequent lateral solidification in order to obtain desirable microstructures. One of the major objectives of the ACSLG processes is to improve device p
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