The Impact Of Channel Processing On IZO-TFTs Stability And Its Mechanism

This paper aims to investigate the impact of channel processing by radio frequency magnetron sputtering (RFMS) on thin film transistors (TFTs). stabilities. Indium-zinc oxide (IZO) based TFTs were fabricated at low temperature. Both the IZO as channel layer and aluminum oxide (Al2O3) as dielectric layer were deposited by RFMS and aluminum electrodes by thermal evaporation. The processing temperature all along is below 100℃, which is compatible with the fabrication of flexible electronics. The prepared IZO-TFT exhibits optimum performance when the deposition time and oxygen partial pressure (Po2) of IZO layer are 8 minutes and 0.24 Pa, respectively, with the saturation mobility of 5.52 cm2/V·s, the threshold voltage (VTH) of 6.09 V, the subthreshold swing of 0.54 V/dec and on/off current ratio of 3× 106. Within our certain experimental parameters, the transfer characteristics of the TFTs move upper left along with the deposition time increasing or Po2 decreasing. Furthermore, these two channel processing parameters have a regular impact on TFTs stabilities.Po2 play a role in IZO films and the electrical performances of IZO-TFTs. As-deposited IZO films have amorphous structure, smooth surface (root mean squre roughness is 0.36 nm at least), and about 87% average transmittance in the visible region. The environmental stability between TFT (Po2=0.16 Pa) and TFT (Po2=0.24 Pa) were made a contrast then. After one month the former’s electrical performance changed a lot while the latter’s stable.On the other hand, the prepared TFTs with different channel deposition time (7.5, 8.0,8.5 min respectively) were subjected to a positive stress at VG=10 V for up to 1500 s, and all the three TFTs showed a typical positive parallel VTH shift, which was mainly contributed to electron trapping in the gate dielectric or at the dielectric/channel interface. What’s more, longer deposition time of IZO layer exacerbated the VTH shift, and bias stressing under simultaneous illumination have a smaller Δ VTH compared with stressing in the dark.