Title :
Amorphous silicon thin film transistors formed by plasma enhanced deposition at 110°C on transparent glass/plastic substrates
Author :
Yang, Chien-Sheng
Author_Institution :
Unipac Optoelectron. Corp., Hsinchu, Taiwan
Abstract :
This article demonstrates good quality amorphous silicon thin film transistors (TFT) fabricated with a maximum processing temperature of 110°C on glass or flexible transparent plastic substrates, using rf plasma enhanced chemical vapor deposition. Hydrogen diluted silane was used for the preparation of the amorphous silicon (a-Si), while SiH4/NH3/N2 or SiH4/NH3 /N2/H2 mixtures were used for the preparation of silicon nitride (SiNx) films. Gate and source/drain metal was sputter deposited molybdenum. Plastic substrates were indium tin oxide (ITO) coated polyethylene terephthalate (PET). Transistors formed, using the same processes, on glass and plastic show linear mobilities of 0.33 and 0.12 cm2/Vs, respectively, with IONIOFF ratios greater than 106. For transistors on glass, the achieved highest linear mobility is 0.54 cm 2/Vs. The stability of transistors was characterized using electrical stress measurements. The threshold voltage shift is 5.0 volt for a typical transistor on glass substrate, using a stress condition of Vg=25 volt, 600 seconds. Without applying electrical stresses, threshold voltages and linear mobilities of all transistors were found to increase with storage time. We suggest that the relaxation of the interface (SiN x/a-Si) through the bond breaking of the weakest Si-Si bonds contributes to the observation
Keywords :
amorphous semiconductors; bonds (chemical); carrier mobility; elemental semiconductors; indium compounds; molybdenum; plasma CVD; semiconductor growth; silicon; silicon compounds; sputter deposition; thin film transistors; tin compounds; 110 C; 25 V; 5 V; 600 s; H2; ITO; InSnO; N2; NH3; PET; Si-Si bonds; Si-SiN-Mo; SiH4; SiH4/NH3/N2; SiH4/NH3/N2/H2; SiNx; TFT; amorphous silicon thin film transistors; bond breaking; electrical stress measurements; flexible transparent plastic substrates; gate metal; hydrogen diluted silane; indium tin oxide coated polyethylene terephthalate; linear mobilities; plasma enhanced deposition; rf plasma enhanced chemical vapor deposition; silicon nitride; source/drain metal; sputter deposited molybdenum; stability; storage time; threshold voltage shift; transparent glass/plastic substrates; Amorphous silicon; Glass; Indium tin oxide; Plasma chemistry; Plasma materials processing; Plasma temperature; Plastics; Silicon compounds; Substrates; Thin film transistors;
Conference_Titel :
Information Display, 1999. ASID '99. Proceedings of the 5th Asian Symposium on
Conference_Location :
Hsinchu
Print_ISBN :
957-97347-9-8
DOI :
10.1109/ASID.1999.762761