Statistical Study of Degradation of Flexible Poly-Si TFTs Under Dynamic Bending Stress

Huaisheng Wang,Wenjuan Zhou,Bin Li,Mingxiang Wang,Dongli Zhang,Mengjun Du,Yang Hu

doi:10.1109/jeds.2022.3148129

Abstract

Degradation of flexible low-temperature poly-Si thin film transistors (TFTs) under dynamic bending cycles is investigated with statistical method. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm{ ON}}$ </tex-math></inline-formula> degradation data of different bending cycles and bending conditions are compared to five different statistical distribution models, and it is determined that the Gamma distribution best fits degradation data. Based on the model, the reliability of TFTs under a given stress condition can be evaluated under two typical application scenarios: (1) reliability prediction for large bending cycles; (2) reliability evaluation based on stress test with limited sample size.

Highlights

CURRENTLY, electronic products become increasingly flexible such as foldable flat panel displays
Under a mechanical stress in either bending or stretch, a large number of thin-film transistors (TFTs) are located within the same stress field and they suffer the same stress
The positive shift of the transfer characteristic is due to bending stress induced traps in the gate insulator (GI) or at the channel/GI interface, and fixed negative charges trapping

Summary

Introduction

CURRENTLY, electronic products become increasingly flexible such as foldable flat panel displays. In case of flexible low temperature poly-Si (LTPS) TFTs under bending stresses, the investigation covers TFT degradation and mechanisms [1,2,3,4], failure analysis [5,6,7], and process or structure optimization [8,9,10]. For mechanical stress induced degradation in flexible TFTs, there is no statistical analysis reported until now. Under a mechanical stress in either bending or stretch, a large number of TFTs are located within the same stress field and they suffer the same stress. In this case, degradation or failure of

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Conclusion