21.4: Zinc Indium Oxide Thin‐Film Transistors for Active‐Matrix Display Backplane

Abstract

We report on the development of low‐temperature gate dielectric materials for zinc indium oxide (ZIO) thin‐film transistors (TFTs). Several films, including ALD HfO2 and PECVD SiNx (deposited at 175°C and 150°C, respectively), yield good TFT performance. Bias stress‐induced threshold shift for HfO2 is quite small, however does not follow conventional trends associated with hydrogenated amorphous Si (a‐Si:H) TFTs; PECVD SiNx conversely, shows bias stress characteristics that conform reasonably to a model appropriate for a‐Si:H devices.

Impact of drain bias stress on forward/reverse mode operation of amorphous ZIO TFTs

“…Although some papers have reported no V th shift with negative gate bias [4][5][6][7][8][9][10], we have found evidence of negative V th drift [14,16]. Moreover varying the drain voltage seems to have no impact on the post stressed forward and reverse currents (shown in Fig.…”

“…Most prior publications point towards charge trapping as the dominant mechanism [10,[13][14][15], although some observations favoring defect creations under high bias have also been reported [14]. While some papers report a logarithmic dependence of V th degradation with time [10,14,15], others have also reported the familiar stretched exponential model of V th degradation [4,16], as in a-Si:H [18].…”

“…In addition to transparency in visible range, they have superior electron mobility and better stability than a-Si:H TFTs [4][5][6][7], which has been the dominant device for flex electronics and flex displays [8]. Higher mobility directly translates into faster performance showing promise for even RFID tags [9].…”

“…Higher mobility directly translates into faster performance showing promise for even RFID tags [9]. Several AOS like Indium zinc oxide (IZO) [4], Indium Gallium Zinc Oxide [10] and Zinc Tin Oxide [11] have been reported and studied. Amorphous Zinc Indium Oxide (a-ZIO) is a promising candidate among these metal oxides.…”

Novel flexible reflective color media with electronic inks

“…HP is developing an active-matrix backplane technology based on transparent metal oxide thin-film transistors (TFTs) that are compatible with existing glass (AMLCD) fabs and that are capable of eventual migration to a R2R manufacturing process [9]. One of the key challenges to achieving a pixelated bright-color reflective device using a stacked architecture is the need to minimize the light absorption through the electronic elements within the optical stack.…”