Performance Enhancement and Bending Restoration for Flexible Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors by Low-Temperature Supercritical Dehydration Treatment

Abstract

For high-performance and high-lifetime flexible and wearable electronic applications, a low-temperature posttreatment method is highly expected to enhance the device performance and repair the defects induced by the low-temperature fabrication process intrinsically. Particularly, if the method can repair the traces induced by the multiple cycles of bending or deforming, it would overcome current fatal obstacles and provide a vital solution to the rapid development of flexible electronics. In this work, we propose a method to apply low-temperature supercritical CO2 fluid with a dehydration function to improve or even restore the performance of flexible amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). After the treatment, the a-IGZO TFT exhibits 3 times improvement drivability up to 0.24 μA/μm, a smaller subthreshold swing of 0.18 V dec–1, a smaller V th of 0.25 V, and a larger I on/I off ratio of 3.8 × 107. Additionally, the posttreated a-IGZO TFTs possess relatively good uniformity and reproducibility with an on-current standard deviation of 0.047 μA/μm, and the performance of the a-IGZO TFT after the treatment remains almost unchanged even after bending 2500 times at a bending radius of 5 mm. These characteristics are attributed to the improved quality of the channel and gate dielectric. It is worth noting that when this is applied to a flexible TFT-driven organic light-emitting diode lighting system, this treatment method can restore the performance of not only the TFT but also the lighting system, even after the system has been bent more than 600 times and has failed. To date, this is the first time that the bending-track erasing function of the supercritical fluid for flexible systems has been reported, which has the potential to prolong the lifetime of flexible electronics.

Analysis of Carrier Behavior for Amorphous Indium Gallium Zinc Oxide After Supercritical Carbon Dioxide Treatment

“…[24] The decreased −OH bonds at the interface together with the improved dielectric result in disappearance of the hump. [18] From the above data and analysis, the post-treated 41-nm a-IGZO TFT shows decreased μ although the rear and front a-IGZO surface was modified by the SCCO 2 . The determining factor for μ is scattering effect.…”

“…After calculation, I on standard deviations of the 19, 28, and 41 nm devices are 9.7%, 10.9% and 12.0%, respectively, indicating comparable uniformity and reproducibility in the fabricated a-IGZO TFTs compared with the state-of-the-art works. [18,20]…”

“…Compared with other methods, SCCO 2 method is more promising due to its low‐temperature process, nondestructive property, ability to remove organic impurities, and restorability from bending. Earlier work [ 18 ] has studied the enhancing effect of this treatment on flexible a‐IGZO devices. To gain maximum advantage of such technique, an understanding of the carrier mechanism beyond the performance enhancement is important.…”

“…[9] Poor-quality of a-IGZO film has hindered the development of commercial applications for a-IGZO thin film transistor (TFT)based electronics. [10][11][12] Many post-treatments such as annealing, [13] microwave irradiation, [14] plasma treatment, [15][16][17] and supercritical carbon dioxide fluid (SCCO 2 ) treatment [18,19] have been implemented to improve a-IGZO film quality. Compared with other methods, SCCO 2 method is more promising due to its low-temperature process, nondestructive property, ability to remove organic impurities, and restorability from bending.…”

Applications and Future Developments of Flexible Organic Light-emitting Diode

“…OLEDs are favored plenty of consumers owing to their advantages e.g., self-emission, low driving voltage, high response speed, high contrast, wide viewing angle, good temperature characteristics, ultra-thin, impact resistance, flexible display etc. They are regarded as the third generation display technology after cathode ray tube (CRT) display and liquid crystal display (LCD) [1], and have gradually become a research hotspot in the display field.…”