“…This is due to a higher number of H-related impurities that formed through silanol condensation in the film during the curing process. 17) These H-related impurities remained in the film as the post-baking temperature was too low to facilitate effective evaporation. But still, the performance of PSQ passivation is comparable to inorganic passivations and much better compared to organic passivation cured at low temperatures.…”
This paper presents a low-temperature solution-processed passivation material based on polysilsesquioxane (PSQ) which greatly improves electrical performance and stability of solution-processed amorphous InZnO (a-IZO) thin-film transistors (TFTs). PSQ-passivated TFTs exhibited maximum mobilities of 6.02 cm2 V−1 s−1 with the smallest threshold voltage shift of 2.8 V after positive bias stress test. We showed that hydrogen-related ions from PSQ passivation help passivate oxygen vacancies, thus improving the percolation path in a-IZO channel. Moreover, PSQ-passivated TFTs showed minimal change after being subjected to humidity stress. These results demonstrate the ability of low-temperature PSQ passivation as an effective barrier against atmospheric effects.
“…This is due to a higher number of H-related impurities that formed through silanol condensation in the film during the curing process. 17) These H-related impurities remained in the film as the post-baking temperature was too low to facilitate effective evaporation. But still, the performance of PSQ passivation is comparable to inorganic passivations and much better compared to organic passivation cured at low temperatures.…”
This paper presents a low-temperature solution-processed passivation material based on polysilsesquioxane (PSQ) which greatly improves electrical performance and stability of solution-processed amorphous InZnO (a-IZO) thin-film transistors (TFTs). PSQ-passivated TFTs exhibited maximum mobilities of 6.02 cm2 V−1 s−1 with the smallest threshold voltage shift of 2.8 V after positive bias stress test. We showed that hydrogen-related ions from PSQ passivation help passivate oxygen vacancies, thus improving the percolation path in a-IZO channel. Moreover, PSQ-passivated TFTs showed minimal change after being subjected to humidity stress. These results demonstrate the ability of low-temperature PSQ passivation as an effective barrier against atmospheric effects.
“…[1][2][3][4][5] However, there are still many issues related to the control of threshold voltage and bias-induced degradation. [6][7][8][9][10][11] Therefore, there have been many studies on improving AOS TFT stability such as high-pressure oxygen annealing, 12 annealing in hydrogen environment, 13 O 2 plasma treatment, 14 suitable passivation materials, 15 long channel TFT 16 and long-time annealing, etc. 17 Especially, the performance of a-IGZO TFT depends on channel length, and the TFTs with channel length less than 2 µm exhibit mostly depletion mode behavior.…”
We report two-step annealing, high temperature and sequent low temperature, for amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) to improve its stability and device performance. The annealing is carried out at 300 oC in N2 ambient for 1 h (1st step annealing) and then at 250 oC in vacuum for 10 h (2nd step annealing). It is found that the threshold voltage (VTH) changes from 0.4 V to -2.0 V by the 1st step annealing and to +0.6 V by 2nd step annealing. The mobility changes from 18 cm2V-1s-1 to 25 cm2V-1s-1 by 1st step and decreases to 20 cm2V-1s-1 by 2nd step annealing. The VTH shift by positive bias temperature stress (PBTS) is 3.7 V for the as-prepared TFT, and 1.7 V for the 1st step annealed TFT, and 1.3 V for the 2nd step annealed TFT. The XPS (X-ray photoelectron spectroscopy) depth analysis indicates that the reduction in O-H bonds at the top interface (SiO2/a-IGZO) by 2nd step annealing appears, which is related to the positive VTH shift and smaller VTH shift by PBTS.
“…It had a small number of hydroxyl groups (21.4%), and there was a slight decrease for the 250 °C-annealed film. Therefore, the solution processed HfO 2 passivation layer is sufficiently oxidized when annealed at 150 °C, and a small number of hydroxyl groups can ensure TFT reliability because dissociated hydrogen from hydroxide bonds can diffuse into a channel and affect the characteristic of TFT 26 , 27 . Figure 5 XPS results for ( a ) the Y 3d spectra of the Y 2 O 3 and ( b ) the Hf 4 f spectra of the HfO 2 passivation layer annealed at 150 °C and 250 °C, and the O 1s spectra of the ( c ) Y 2 O 3 and ( b ) HfO 2 passivation layer annealed at 150 °C, and the ( e ) Y 2 O 3 and ( f ) HfO 2 passivation layer annealed at 250 °C.…”
We report low-temperature solution processing of hafnium oxide (HfO2) passivation layers for amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs). At 150 °C, the hafnium chloride (HfCl4) precursor readily hydrolyzed in deionized (DI) water and transformed into an HfO2 film. The fabricated HfO2 passivation layer prevented any interaction between the back surface of an a-IGZO TFT and ambient gas. Moreover, diffused Hf4+ in the back-channel layer of the a-IGZO TFT reduced the oxygen vacancy, which is the origin of the electrical instability in a-IGZO TFTs. Consequently, the a-IGZO TFT with the HfO2 passivation layer exhibited improved stability, showing a decrease in the threshold voltage shift from 4.83 to 1.68 V under a positive bias stress test conducted over 10,000 s.
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