A new device structure of oxide thin‐film transistor (TFT) having lower overlap capacitance without scarifying the drain current is proposed. This can be used for high‐speed circuits and high frame rate displays using the conventional TFT manufacturing process. The existence of spreading currents in amorphous indium‐gallium‐zinc oxide (a‐IGZO) TFTs with stripe‐patterned source/drain (S/D) electrodes is demonstrated. The device performances of the a‐IGZO TFTs with various widths of stripe‐patterned S/D electrodes and open spaces between them are compared. The drain currents of the a‐IGZO TFTs are almost same when the width of open space changes from 0 to 10 µm because of the existence of spreading currents. The overlap capacitance between gate and S/D of the a‐IGZO TFTs can be significantly reduced without scarifying drain currents by using stripe‐patterned S/D electrodes. The operation frequency of the ring oscillator made of the TFTs with stripe S/D electrodes with 10 µm open space width is 2.5 times that made of the conventional a‐IGZO TFTs. This spreading current concept can be widely used for the design of oxide TFT array with low RC (resistance capacitance product) delay for high‐speed circuits.
We report the performance improvement of low-temperature coplanar indium–gallium–zinc–oxide (IGZO) thin-film transistors (TFTs) with a maximum process temperature of 230 °C. We treated F plasma on the surface of an SiO2 buffer layer before depositing the IGZO semiconductor by reactive sputtering. The field-effect mobility increases from 3.8 to 9.0 cm2 V−1·s−1, and the threshold voltage shift (ΔVth) under positive-bias temperature stress decreases from 3.2 to 0.2 V by F-plasma exposure. High-resolution transmission electron microscopy and atom probe tomography analysis reveal that indium fluoride (In-F) nanoparticles are formed at the IGZO/buffer layer interface. This increases the density of the IGZO and improves the TFT performance as well as its bias stability. The results can be applied to the manufacturing of low-temperature coplanar oxide TFTs for oxide electronics, including information displays.
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