Effects of Thermal Annealing on ZnO Thin-Film Transistor Characteristics and the Application of Excimer Laser Annealing in Plastic-Based ZnO Thin-Film Transistors

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In this paper, we present the effects of thermal annealing and excimer laser annealing (ELA) on the characteristics of zinc-oxide (ZnO) thin-film transistors (TFTs) fabricated by magnetron sputtering at room temperature. The transfer characteristics of the ZnO-TFTs are found to improve with increasing thermal annealing temperature. Results of in situ high-temperature X-ray diffraction and electron back scattered diffraction pattern analyses indicate that this phenomenon arises from the crystallization of a low-crystallinity region present in as-deposited ZnO films. Almost all low-crystallinity regions crystallize at temperatures above 500 °C. Furthermore, to achieve such high-performance TFTs on flexible plastic substrates, ZnO-TFTs on a plastic substrate were irradiated with an excimer laser to raise the temperature of the ZnO films. Because of the extremely short pulse width of the laser (25 ns), it is possible to selectively increase the temperature of the ZnO with negligible thermal damage to the plastic substrate. The ELA process has enabled us to produce flexible high-performance ZnO-TFTs with a field-effect mobility of 12 cm2 V-1 s-1.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2009-08-25