Uniform Crystallization of a 3" Amorphous-Si TFT Array Employing Field-Aided Lateral Crystallization

In high-resolution displays, such as liquid crystal displays and organic light emitting diode displays, pixel-to-pixel uniformity in the panel is one of the most important requirements. In this study, a 120 X 320 thin-film transistor (TFT) array was fabricated on three-inch glass substrates by using Ni-induced, field-aided lateral crystallization (FALC) to improve the crystallization uniformity of a-Si below 500 degrees C. Two specially-designed common electrodes connecting the sources and the drains of the transistors in the array enabled application of a uniform electric field to the individual transistors during the FALC process. Thermal annealing at 500 degrees C for 4 hours completely crystallized the 20-mu m-long channels of the TFTs. The degree of crystallization and the electrical properties of the TFTs were very uniform with a deviation of less than a few percent, which indicates that the proposed common electrode design and the FALC process can be used in applications.