Alleviation of abnormal NBTI phenomenon in LTPS TFTs on polyimide substrate for flexible AMOLED

Lee, Jaeseob; Lee, Byoung Hun; Kang, Taewook; Chu, Hye-Yong; Kwag, Jinoh

doi:10.1002/jsid.883

Cited by 23 publications

(15 citation statements)

References 19 publications

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“…This abnormal behavior is alleviated by the insertion of the bottom metal layer to block the diffusion of H from the PI substrate. [13,14] Fig. 5 shows the normal NBTI behavior, that is, negative Vth shift and increase of both Nit and Ntrap in the unstrained, transvrse tensile-and compressive-strained 4-terminal double-gate (4-T DG) LTPS TFTs on PI.…”

Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

5‐2: Enhanced Bending Endurance with Transverse Tensile Strain and 4‐Terminal Double Gate LTPS TFTs for flexible AMOLED

Lee

Kang

et al. 2021

Symp Digest of Tech Papers

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This letter investigates the degradation behavior of p‐channel LTPS TFTs on PI substrate under the static bending stress. During 1hr bend, the threshold voltage shifts positively and the subthreshold slope increases slightly. In transverse compressive strain, the field effect mobility increases abruptly with the decrease of the effective channel length and the off state leakage current. This is attributed to the generation of the strain‐induced GI defects near the source and drain terminals, resulting in the trapping of electrons and a shrinkage of the effective channel length and the H passivation of the strained Si bonds in the channel. By inserting the bottom metal layer to block the H diffusion from PI substrate, the controllable normal NBTI behavior is observed in a strained LTPS TFT on PI. These transverse tensile strained and 4‐termianl double gate LTPS TFTs on PI shows as a stable switching TFTs on PI for the flexible system‐on‐panel display.

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Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

5‐2: Enhanced Bending Endurance with Transverse Tensile Strain and 4‐Terminal Double Gate LTPS TFTs for flexible AMOLED

Lee

Kang

et al. 2021

Symp Digest of Tech Papers

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“…Grain boundary trap states of LTPS TFTs can be extracted by Levinson and Proano method. [9,10] Considering the effect of the grain boundaries in the active layer, the drain current of LTPS TFTs can be expressed as…”

Section: Interface Trap and Grain Boundary Trapmentioning

confidence: 99%

3‐2: Invited Paper: Instability Issues of LTPS TFT for High Performance of Flexible AMOLED Display

Zhao

Chen

Xing

et al. 2021

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We present here a combined theoretical and experimental investigation on hysteresis improvement of LTPS TFTs via optimizing hydrogen content in poly‐silicon and adjusting density of states at poly‐Si/oxide interface. It can be demonstrated that hysteresis seems to be more dependent on the difference in trap density between the bandedge and midgap energy levels. A new method named just noticeable current difference (JND_Current) is employed to evaluate TFT reliability and short‐term image sticking. Incorporating the optimized processes of a‐Si deposition, cleaning conditions before gate‐insulator (GI) deposition and contact hole annealing is helpful to improve instability of LTPS TFTs. The hysteresis level (ΔVth) can be reduced to 0.11V, and also an improvement in quantized level of short‐term image sticking by 35%.

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“…Especially, commonly used TFTs including LTPS and a-IGZO TFT that adopt new features such as low frequency and always-display-on are susceptible to charge-induced degradation and image retention 25,28 . One of the feasible solutions proposes a metal layer deposition underneath the channel above the PI substrate for blocking PI charging 29,30 . However, the details about the blocking mechanism have not been fully investigated.…”

Section: Introductionmentioning

confidence: 99%

Highly Reliable Flexible Device With Charge Compensation Layer

Kim

Park

Khim

et al. 2022

Preprint

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Flexible devices fabricated with polyimide (PI) substrate are crucial for foldable, rollable, or stretchable products in various applications. However, inherent technical challenges remain in mobile charge induced device instabilities and image retention, significantly hindering future technologies. We introduced a new barrier material, SiCOH, into the backplane of amorphous indium-gallium-zinc-oxide (a–IGZO) thin-film transistors (TFTs) that were then implemented into production-level flexible panels. We found that the SiCOH layer effectively compensates the surface charging induced by fluorine ions at the interface between the PI substrate and the barrier layer under bias stress, thereby preventing abnormal positive Vth shifts and image disturbance. The a–IGZO TFTs, metal-insulator-metal (MIM), and metal-insulator-semiconductor (MIS) capacitors with the SiCOH layer demonstrate reliable device performance, Vth shifts, and capacitance changes with an increase in the gate bias stress. A flexible device with SiCOH enables the suppression of abnormal Vth shifts associated with PI and plays a vital role in the degree of image sticking phenomenon. This work provides new inspirations to creating much improved process integrity and paves the way for expediting versatile form-factors.

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Alleviation of abnormal NBTI phenomenon in LTPS TFTs on polyimide substrate for flexible AMOLED

Cited by 23 publications

References 19 publications

5‐2: Enhanced Bending Endurance with Transverse Tensile Strain and 4‐Terminal Double Gate LTPS TFTs for flexible AMOLED

5‐2: Enhanced Bending Endurance with Transverse Tensile Strain and 4‐Terminal Double Gate LTPS TFTs for flexible AMOLED

3‐2: Invited Paper: Instability Issues of LTPS TFT for High Performance of Flexible AMOLED Display

Highly Reliable Flexible Device With Charge Compensation Layer

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