Enhancing Repetitive Uniaxial Mechanical Bending Endurance at ${R} = 2$  mm Using an Organic Trench Structure in Foldable Low Temperature Poly-Si Thin-Film Transistors

Huang, Shin-Ping; Zheng, Yu‐Zhe; Chang, Ting‐Chang; Chen, Bo-Wei; Chen, Po-Hsun; Chu, Ann-Kuo; Chen, Hong-Chih; Tsao, Yu‐Ching; Chen, Min-Chen; Chen, Wei-Han; Wang, Terry Tai-Jui; Kanicki, Jerzy; Zhang, Shengdong

doi:10.1109/led.2019.2909966

Cited by 14 publications

(9 citation statements)

References 24 publications

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“…This is due to the increases of defects after repeated mechanical bending at the poly‐Si/SiO 2 interface and GI. [ 18,24,25 ] Note that the Young's moduli of the SiO 2 and SiN x are 70 and 250 GPa, respectively, and these inorganic materials have much higher moduli than that (2.5 GPa) of PI. Therefore, the stress in the GI and poly‐Si/SiO 2 interface is much higher as compared to that using PI.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the stress in the GI and poly‐Si/SiO 2 interface is much higher as compared to that using PI. [ 25 ] Therefore, the LTPS TFTs with inorganic ITL have more degradation under repetitive bending stress. In addition, it can be clearly seen that tensile bending induces more degradation than compressive bending.…”

Section: Resultsmentioning

confidence: 99%

“…The effects of mechanical strain and electrical reliability of LTPS TFTs have been previously reported (show in Table 1 ) with the conclusion that the mechanical stability is inferior to oxide TFTs. [ 15–30 ] Therefore, finding a solution to overcome the performance degradation during mechanical stress is important for more flexible and foldable AMOLED displays.…”

Section: Introductionmentioning

confidence: 99%

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Poly‐Si Thin‐Film Transistors on Polyimide Substrate for 1 mm Diameter Rollable Active‐Matrix Organic Light‐Emitting Diode Display

et al. 2021

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Recently, flexible displays based on active-matrix organic lightemitting diode (AMOLED) on polyimide (PI) substrate are of increasing interest for use in foldable displays. PI substrates are not only thin and light, [1,2] but also could be processed at relatively high temperature (≥450 C). To achieve a flexible AMOLED display, thin-film transistor (TFT) array should be manufactured on a plastic substrate. [3][4][5][6][7][8][9][10][11] Popular semiconductor materials used for TFTs are amorphous silicon (a-Si), amorphous indium-gallium-zinc-oxide (a-IGZO), and polycrystalline Si (poly-Si) on PI substrate. Due to its low-temperature process on large glass substrates such as 10.5G (2.2 m Â 2.5 m), the a-Si:H has been used as a TFT switching element. However, it cannot be used for AMOLED TFT backplanes because of its threshold voltage (V TH ) shift during OLED operation. [12,13] Note that a-IGZO TFT has at least one order of magnitude higher mobility compared to a-Si:H TFT even though the TFT process temperature is similar. The a-IGZO TFT can be manufactured by using G10.5 glass so that manufacturing cost of oxide TFT backplanes for OLED can be much lower than that of low-temperature poly-Si (LTPS) TFT. Therefore, intensive studies on amorphous oxide semiconductors are being carried out for TFT backplanes of OLED displays. However, all smartphone OLED displays are still based on LTPS TFT backplanes because of its high mobility and excellent stability. The LTPS TFTs on PI substrate with high mobility and high stability are very suitable for mobile application. [14] The effects of mechanical strain and electrical reliability of LTPS TFTs have been previously reported (show in Table 1) with the conclusion that the mechanical stability is inferior to oxide TFTs. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Therefore, finding a solution to overcome the performance degradation during mechanical stress is important for more flexible and foldable AMOLED displays.In this article, to improve the reliability under mechanical stress, flexible LTPS TFTs were fabricated using three kinds of interlayers (ITLs): inorganic (SiO 2 /SiN x ), hybrid (SiN x /PI), and organic (PI) layers. Reliability test of the LTPS TFTs is performed using bending and rolling machines until 10 000 cycles. Using low Young's modulus organic material (PI) ITL, the change in electrical performance under mechanical strain could be reduced significantly. Especially, rolling test with rolling radius of 1 mm was examined until 10 000 cycles. The LTPS TFT with inorganic ITL shows the crack generation after rolling with 1 mm radius. However, the performance of the LTPS TFTs with hybrid ITL

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Poly‐Si Thin‐Film Transistors on Polyimide Substrate for 1 mm Diameter Rollable Active‐Matrix Organic Light‐Emitting Diode Display

et al. 2021

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“…Chen et al reported that positive gate sweep after mechanical stress on poly‐Si TFT causes the electron trapping at GBs. [ 29,30 ] Therefore, the V TH shifts to positive after out‐folding stress. If the atomic bonds in poly‐Si and SiO 2 are broken or weakened, O, H, and hydroxyl (OH) could be formed inside the GI and GI/poly‐Si interface.…”

Section: Resultsmentioning

confidence: 99%

“…The electrical stability of the LTPS TFT can be affected by the mechanical strain. [ 26–34 ] Contrastingly, electro‐thermal (positive bias temperature stress (PBTS) or negative bias temperature stress (NBTS) after mechanical strain [ 35 ] can also severely deteriorate the electrical characteristics, which needs to be further studied.…”

Section: Introductionmentioning

confidence: 99%

Excellent Mechanical Durability of In‐Folding Stress of Poly‐Si Thin‐Film Transistor on Plastic Substrate Compared with Out‐Folding: Generation of Gate Leakage Currents in Flexible Poly‐Si Thin‐Film Transistor by Out‐Folding and Bias‐Temperature Stress

et al. 2020

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The effect of electro‐thermal stress on the electrical performance of flexible, low‐temperature polysilicon (LTPS) thin‐film transistors (TFTs) after mechanical‐folding stress aiming to improve the reliability of foldable display backplanes is studied (IG). Herein, for the first time, the significant increase of gate leakage currents upon the negative bias temperature stress (NBTS) or positive bias temperature stress (PBTS) after the out‐folding test on excimer laser annealing (ELA) TFTs is reported. Out‐folding stress increases the drain current, shifts the threshold voltage (ΔVTH) by 2.4 V, and increases the subthreshold swing without affecting the (IG). However, the ΔVTH is 1.8 V upon NBTS, and the negative ΔVTH is −4.7 V upon PBTS after out‐folding stress along with a drastic increase in IG. A thermal annealing at 250 °C for 10 h for the electro‐thermal stressed TFTs after out‐folding is performed, and initial electrical characteristics recovery is achieved; except the abruptly increased IG. These results are correlated with charge trapping at the damaged grain boundary and (GI). A model with moisture/water molecule diffusion through the nanocracks generated by out‐folding is proposed. The ionized charges (H+, OH−) captured at the nanocrack‐induced trap sites in poly‐Si and GI appear to be the origin of abnormal ΔVTH and IG.

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Thin‐Film Transistors for Integrated Circuits: Fundamentals and Recent Progress

Yan,

Wang,

Yan

et al. 2023

Adv Funct Materials

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High‐performance thin‐film transistors (TFTs) integrated circuits (ICs) have become increasingly necessary to meet the emerging demands such as healthcare, edge computing, and the Internet of Things, etc. This article aims to point out the potential development trends and bottlenecks of TFT ICs, enhancing their performance in terms of electronic performance, stability, consistency, CMOS design, and manufacturing capability. Basic device structures and overall metrics of TFT ICs are explored, as well as their superiority compared to silicon‐based ultrathin chips. Hydrogenated amorphous silicon, low‐temperature polycrystalline silicon, and amorphous oxide semiconductors are widely used in displays due to their ability to be deposited on large areas at low processing temperatures and low cost, and are validated in many prototypes for TFT ICs. Their conduction mechanisms, process flows, performance evaluation, and recent advances are comprehensively viewed. In addition, the potential of emerging low‐dimensional materials as next‐generation channel materials is discussed, along with their limitations and progress in this field. Finally, the major challenges in manufacturing high‐performance TFT ICs and future perspectives are summarized.

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Enhancing Repetitive Uniaxial Mechanical Bending Endurance at ${R} = 2$ mm Using an Organic Trench Structure in Foldable Low Temperature Poly-Si Thin-Film Transistors

Cited by 14 publications

References 24 publications

Poly‐Si Thin‐Film Transistors on Polyimide Substrate for 1 mm Diameter Rollable Active‐Matrix Organic Light‐Emitting Diode Display

Poly‐Si Thin‐Film Transistors on Polyimide Substrate for 1 mm Diameter Rollable Active‐Matrix Organic Light‐Emitting Diode Display

Excellent Mechanical Durability of In‐Folding Stress of Poly‐Si Thin‐Film Transistor on Plastic Substrate Compared with Out‐Folding: Generation of Gate Leakage Currents in Flexible Poly‐Si Thin‐Film Transistor by Out‐Folding and Bias‐Temperature Stress

Thin‐Film Transistors for Integrated Circuits: Fundamentals and Recent Progress

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