Non-ideal current drop behavior in ultra-thin inorganic a-InGaZnO thin film transistors

Recent research in flexible and imperceptible electronic devices has been dominated by the development of robust channel materials and adequate processes for thin-film transistors (TFTs) based on an inorganic amorphous oxide. Water-soluble sacrificial polyvinyl alcohol and parylene were employed for the fabrication of ultra-light amorphous In–Ga–Zn–O (a-IGZO) TFTs with a top-gate configuration. But, a higher negative gate bias stress (≥5 V) caused anomalous degradation in the on-current level and field-effect mobility with increasing stress time, which was attributed to the rough surface of the chemical vapor deposited parylene film. The current work adopts an ultraviolet ozone irradiation treatment for improving the surface roughness of the polymer films prior to the fabrication of oxide TFTs. A suppression of the on-current drop and typical TFTs transfer behavior were observed under light irradiation with a negative gate bias stress. The a-IGZO TFTs on the parylene surface treated for 20 min exhibited a device thickness of approximately 5 µm and good TFT performances with field-effect mobility, subthreshold swing, and on/off current ratio values of 13.9 cm²/V s, 0.24 V/dec, and 7 × 10⁸, respectively. This survey suggests that a polymer film with a smooth surface can play a beneficial role in fabricating flexible ultra-slim a-IGZO TFTs.