Enhanced performance and stability of a-ZTO TFTs via off-axis sputtering: impact on defect density and channel stability

초록

ON-axis and OFF-axis RF sputtering configurations have been compared to analyze their effects on the device performance and reliability of amorphous Zinc-Tin-Oxide (a-ZTO) thin-film transistors (TFTs). The OFF-axis deposited TFTs exhibited superior electrical characteristics with a field-effect mobility of 26.4 cm2 V-1 & centerdot;s-1, threshold voltage of 3.31 V, and an excellent Ion/Ioff ratio of 3.08 & times; 1011, significantly outperforming the ON-axis configuration. Temperature stress tests, positive bias stress (PBS), and comprehensive analysis including transfer and output characteristics revealed that OFF-axis deposited devices exhibited a significantly lower density of states (DOS), indicating better structural channel stability. X-ray photoelectron spectroscopy further confirmed that OFF-axis deposition produced a moderate amount of shallow donor-like oxygen vacancies while suppressing deep interfacial defects, consistent with the reduced DOS and improved stability. Transmission line method measurements showed reduced contact and sheet resistances, reflecting improved electrode/channel interface quality. These results clearly demonstrate that OFF-axis sputtering effectively tailors defect distributions and interfacial quality, leading to both superior performance and stability in oxide TFTs.

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