Top Interface Engineering of Flexible Oxide Thin‐Film Transistors by Splitting Active Layer

Abstract

The effect of active layer (amorphous indium–gallium–zinc oxide, a‐IGZO) splitting on the performances of back‐channel‐etched (BCE) and etch‐stopper (ES) thin‐film transistors (TFTs) on polyimide substrate is studied. While the performance of BCE TFT is independent of active layer splitting, the performance of ES TFT is improved significantly by splitting the active layer into 2–4 µm width along the channel. The saturation mobility is enhanced from 24.3 to 76.8 cm2 V−1 s−1 and this improvement is confirmed by the operation of a ring oscillator made of the split TFTs also. X‐ray photoelectron spectroscopy (XPS) analysis of the split a‐IGZO indicates the incorporation of F at the island interface and thus improves the top interface quality, leading to a significant improvement of the top channel TFT mobility from 0.25 to 24.22 cm2 V−1 s−1. This improvement is correlated with bonding of In with F at the top interface according to XPS results. The bias stability, hysteresis, and mechanical stability of the ES a‐IGZO TFT are also remarkably improved by splitting a‐IGZO active layer.

Top-down Fabrication and Enhanced Active Area Electronic Characteristics of Amorphous Oxide Nanoribbons for Flexible Electronics

“…On/off ratios of NR TFTs are over 10 7 showing a tendency of slight decrease in on/off ratio after being etched. Effective field-effect mobility ( μ FE )was extracted using the following equation 28 :where V D is drain voltage (set at 10 V), L is the device length (fixed as 10 μm), and C i is the gate capacitance per unit area. C i value is experimentally obtained by a metal-insulator-semiconductor capacitor of 34.5 nF/cm 2 (Supplementary Fig.…”

Highly robust oxide TFT with bulk accumulation and source/drain/active layer splitting

“…Schematic cross sections of the DG TFT on PI substrate with split active structures along the channel length (BB’) and along the channel width (AA’) are shown in Figure E and F, respectively. The detailed fabrication process of the DG a‐IGZO TFTs on PI substrate as described elsewhere . First, the formation of a Carbon nano tube (CNT): Graphene oxide (GO) release layer on carrier glass by spin coating and then spin coating of a PI layer and multilayer gas barrier consisting of SiO 2 /SiNx is deposited through plasma‐enhanced chemical vapor deposition (PECVD) on top of the PI, followed by the formation of BG electrode.…”

“…The unique properties of oxide‐based semiconductors such as wide bandgap and high transparency also make novel applications possible. For example, a see‐through type transparent AMOLED can be realized using oxide based semiconductor . Using such types of displays, one can see the objects in the opposite side of the displays, and thus many interesting applications can be possible.…”

“…And, we reported the advantages of the split active layer used for etch‐stopper (E/S) oxide TFTs. The mobility can be over 70 cm 2 /Vs and the low sub‐threshold swing (SS) and there are stable under the bias, temperature, and mechanical stress . In addition, we reported that the micron size patterning (split) of source, drain, and gate electrodes as well as of the a‐IGZO semiconductor layer improves TFT robustness under mechanical bending strain .…”

“…The mobility can be over 70 cm 2 /Vs and the low sub-threshold swing (SS) and there are stable under the bias, temperature, and mechanical stress. 13,14 In addition, we reported that the micron size patterning (split) of source, drain, and gate electrodes as well as of the a-IGZO semiconductor layer improves TFT robustness under mechanical bending strain. 15,16 To prevent the extension of cracks in semiconductor and source/drain (S/D) electrode layer, split both electrodes and semiconductor can be used.…”