Fabrication and characterization of ferroelectric-gate thin-film transistors with an amorphous oxide semiconductor, amorphous In-Ga-Zn-O

We fabricated and characterized ferroelectric-gate thin-film transistors (FeTFTs) with an amorphous In Ga Zn-O (a-IGZO) channel and an oxide ferroelectric (Bi,La)(4)Ti3O12(BLT) gate insulator, and examined the fabrication conditions beforehand for realizing ferroelectric hysteresis in their drain current versus gate voltage (I-D-V-G) characteristics. First, the optimal annealing conditions for BLT-thin-film formation by the sol gel method were considered in terms of chemical phenomena and crystallization mechanism. As a result, the leakage current density of the film was decreased by more than two orders of magnitude. Second, sputtering deposition conditions and postdeposition annealing temperatures of a-IGZO thin films were investigated to prepare the a-IGZO channel with good electrical properties. A small charge-injection-type hysteresis width of 0.2V was obsereved in I-D-V-G characteristics of a-IGZO/SiO2 TFTs. Finally, a-IGZO/BLT FeTFTs were fabricated using the above results, and the ferroelectric hysteresis with a width of 0.4 V was observed. (C) 2014 The Japan Society of Applied Physics