Polycrystalline Silicon Thin Film Transistors

摘要

Polycrystalline silicon thin film transistors (poly-Si TFTs) have been widely applied to switching elements for liquid-crystal and organic electroluminescent displays used in note book type personal computers, mobile phones and televisions (1). Application of TFTs to logical integrated circuits have also proceeded because of their capability of a high operation frequency (2,3). Fabrication of TFT circuits on plastic films is attractive for cheap, flexible and light devices. Fabrication processes of TFTs at low temperatures are essential for those purposes. In this paper, we review technologies of poly-Si film formation. We also discuss electrical and structural properties of poly-Si films. Low temperature processing of poly-Si TFTs is then discussed. Many important technologies have been developed during recent twenty years. Formation of SiO_2 gate insulator is essentially important for TFT fabrication as well as poly-Si formation. Defect passivation is necessary for high performance poly-Si TFT fabrication. Transfer technology is also interesting. Development in evaluation methods of electrical properties of poly-Si and TFTs has much contributed to improvement in TFT processing. Finally, we discuss capability of TFT performance and possibility of application to electronic devices in future.