A Novel Structural Design Serving as a Stress Relief Layer for Flexible LTPS TFTs

Wang, Yu-Xuan; Chang, Ting‐Chang; Huang, Shin-Ping; Tai, Mao‐Chou; Zheng, Yu‐Zhe; Wu, Chia‐Ching; Sze, Simon M.

doi:10.1109/iedm19573.2019.8993456

Cited by 5 publications

(10 citation statements)

References 7 publications

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“…These newly generated trap states near and at the interface is proportional to the strain amount. [1,2,4,5] The decrease of Ntrap is contrary with the previous studies. It is reported that the Ntrap increases during the static bending on glass substrate or metal foil and the dynamic cyclic bending on PI substrate.…”

Section: -1 IV Characteristics Under the Mechanical Bending Stresscontrasting

confidence: 95%

“…[4,5,9~12] And the off-state leakage current is dependent with the grain boundary traps. [2,5,10] That means that the off current is due to the thermionic field emission via grain-boundary traps in the surface depletion region at the drain terminal. The reduced off current is coincident with the reduction of grainboundary trap state density (Ntrap) as shown in fig.…”

Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

“…This increases ΔLeff. [2,6] We propose that the transverse compressive strain is high enough to generate the GI defects near the source and drain. Also, ΔLeff in non-strained TFTs, 0.79~0.81μm, is similar with the previously reported data, where ΔLeff is 0.77~0.87μm for the p-channel LTPS TFTs.…”

Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

“…[1~3] Also, the subthreshold slope (SS) increases through the generation of interface states and/or the barrier height lowering between source and channel by electron injection into GI, which is proposed to be severe at the poly-Si/SiO2 edge. [1,2,4,5] Field effect mobility also change. The mechanical stress induces an generation of grain boundary trap states, resulting in the decrease of mobilty.…”

Section: Introductionmentioning

confidence: 99%

“…[1,5] On the other hand, the inhomogeneous trap generation in the GI near the source and drain terminals induces electron trapping, resulting in the decrease of the effective channel length, which come to an increase of transconductance in p-channel TFTs. [2,6] Not only the trap state density change but also the integral effects from lattice torsion and carrier effective mass change can also influence on the carrier mobility. Under the biaxial tensile or biaxial tensile plus additional longitudinal uniaxial tensile strain, hole mobility increases by the decrease of the scattering rate through the split of the energy band.…”

Section: Introductionmentioning

confidence: 99%

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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 Stresscontrasting

confidence: 95%

Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

Section: -1 IV Characteristics Under the Mechanical Bending Stressmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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A Stacked p‐Type Low‐Temperature Polycrystalline Silicon Thin‐Film Transistor for Future Display Applications

Wang

Tai

Chang

et al. 2022

Adv Materials Technologies

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In this study, a novel structural design of the p‐type low‐temperature polycrystalline silicon thin‐film transistors (p‐type LTPS TFTs) applied to the pixel structure of displays is proposed. Compared to the conventional pixel structure of displays, the proposed architecture can achieve the aperture ratio improvement by stacking the switch thin‐film transistor and the storage capacitor in a pixel region to enlarge the active space. Therefore, the demands of high‐resolution characteristics, such as a high aperture ratio, and high pixel densities for high‐end displays or novel technologies, can be satisfied by the adoption of the proposed design concept. Furthermore, the discussion of experimental and simulated results in terms of device physics of the transistor indicates that proposed TFTs possess higher performance and reliability properties. By modulating the geometry of the drain‐connected bottom metal in stacked TFTs, output characteristics and hot carrier phenomenon in devices can be further improved. Time‐dependent transfer characteristics, extracted electrical parameters, and numerical simulation results are performed to support our design.

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P‐29: Influence of the Static Bending Stress on LTPS TFT

Guo¹,

Chen²,

Yuan³

et al. 2022

Symp Digest of Tech Papers

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We investigated the degradation behavior of p‐channel LTPS TFTs on PI substrate under the static bending stress. In order to evaluate the bending durability of flexible LTPS TFTs, device‐bending tests under different bending strains and directions have been performed. The performance of TFT under tensile bending stress degraded (ΔVth≈ 0.38V) worse than compressive bending stress (ΔVth ≈0.07V), which might be originated from both the generation of interface trap states (ΔNit) and channel boundary trap density (ΔNtrap) under tensile bending stress much higher than compression‐bent. In the meanwhile, the stress distribution has also been simulated. According to the results of test and simulation, we speculated the mechanical stress near the source and drain electrodes caused the traps in gate insulator, which in turn cause electron trapping.

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A Novel Structural Design Serving as a Stress Relief Layer for Flexible LTPS TFTs

Cited by 5 publications

References 7 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

A Stacked p‐Type Low‐Temperature Polycrystalline Silicon Thin‐Film Transistor for Future Display Applications

P‐29: Influence of the Static Bending Stress on LTPS TFT

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