A series of gas barrier films on colorless polyimide substrates are studied at G4.5 backplane. The performances of barrier layer and TFT are identified by the film‐forming temperature, film structure, reliabilities, NBTIS and WVTR. The use of a SiNx‐SiOx (100nm–500nm) at PECVD temperature 285/295 °C resulted in the best light transmittance and reliabilities, and the electrical properties of a‐IGZO TFTs on glass is better than on cPI. The WVTR value of the SiNx‐SiOx (100nm–500nm) barrier layer on cPI are calculated to be 8.5×10 −5 g/(m 2 ‐day) at 37.8°C/100% RH, the NBTIS are improved after LLO and are deterioration after WVTR test. It is believed that the moisture and hydrogen diffusion from the underlying layers including cPI and environment atmosphere can be effectively suppressed by SiNx‐SiOx (100nm–500nm) barrier, and a flexible array backplane is demonstrated by means of these methods.
We successfully realized 14 inch flexible LCD display with FHD resolution. The LCD panel has the thickness less than 0.3 mm, which using new type of colorless PI as substrate. The flexibel LCD is IPS mode. The key technology includes the conbination of indium gallium zinc oxide (IGZO) TFT, Color filter on Array substrate(COA)and Black Photo Spacer(BPS).
In this work, a novel thin film transistor (TFT) structure named ASD was prepared, which means active layer bottom‐contact with source/drain(SD) layer. ASD device use the first light shield metal layer served as SD electrode simultaneously, which can reduce 2‐count‐mask array process compared with traditional top gate (TG) device. The mobility and subthreshold swing of the ASD a‐IGZO TFT device can reach 14 cm2/Vs and 0.18 V/dec, respectively. The PBTS and NBTIS are within 0.5V through process optimization. In addition, a 7.1 inch Micro‐LED display used ASD TFT backplane has demonstrated, and Finally, the Micro‐LED panel shows +0.7V Vth shift after the high temperature and high humidity operation (HTHHO) 500h reliability test.
Five process improvements for protecting the Micro LED display from HTHHO were evaluated by measuring the Vth shift of top‐gate IGZO TFT backplane. The results showed that the Vth value of Micro LED backplane was placed at HTHHO (60 °C, 90% RH) for 1000h drifted less than 1.5V after protected by the inorganic/ organic film of TF‐1/TF‐2.
In this paper, we disscuss the influence of measuring environment on the leakage current and Vth of ESL (Etching‐Stop‐Layer structure) and TG‐SA (Top‐Gate self‐aligned structure) a‐IGZO TFTs. Hydrogen and oxygen in air can accumulate on the surface of TFTs, forming electrode with floating potential. This layer coupled with input signal potential, results in I off increasing in both structure, and V th shifting negatively in the ESL structure.
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