Charging Compensation Layer on Polyimide for Enhanced Device Stability in Flexible Technology

Bak

et al. 2021

Sci Rep

Self Cite

Flexible displays on a polyimide (PI) substrate are widely regarded as a promising next-generation display technology due to their versatility in various applications. Among other bendable materials used as display panel substrates, PI is especially suitable for flexible displays for its high glass transition temperature and low coefficient of thermal expansion. PI cured under various temperatures (260 °C, 360 °C, and 460 °C) was implemented in metal–insulator–metal (MIM) capacitors, amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFT), and actual display panels to analyze device stability and panel product characteristics. Through electrical analysis of the MIM capacitor, it was confirmed that the charging effect in the PI substrates intensified as the PI curing temperature increased. The threshold voltage shift (ΔVth) of the samples was found to increase with rising curing temperature under negative bias temperature stress (NBTS) due to the charging effect. Our analyses also show that increasing ΔVth exacerbates the image sticking phenomenon observed in display panels. These findings ultimately present a direct correlation between the curing temperature of polyimide substrates and the panel image sticking phenomenon, which could provide an insight into the improvement of future PI-substrate-based displays.

Section: Resultsmentioning

confidence: 99%

Effects of polyimide curing on image sticking behaviors of flexible displays

Bak

et al. 2021

Sci Rep

Self Cite

“…The hole carriers inject into the PI and break chemical bonds in the organic chains. Then, the ions such as F − generated from the broken bonds of the chains act as charged defects and increase the leakage current through the capacitors 27,32 .…”

Section: Electrical and Physical Characteristics Of The Mim And Mis C...mentioning

confidence: 99%

“…Such PI charging is detrimental, particularly for exible electronic products fabricated with the PI substrate. It has been reported that charge-induced V th shifts in TFTs on PI substrates lead to residual images that ultimately impact display image quality 26,27 . 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 .…”

Section: Introductionmentioning

confidence: 99%

Highly Reliable Flexible Device with a Charge Compensation Layer

ACS Appl. Mater. Interfaces

Khim

et al. 2022

Self Cite

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, signi cantly hindering future technologies. We introduced a new barrier material, SiCOH, into the backplane of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-lm transistors (TFTs) that were then implemented into production-level exible panels. We found that the SiCOH layer effectively compensates the surface charging induced by uorine ions at the interface between the PI substrate and the barrier layer under bias stress, thereby preventing abnormal positive V th shifts and image disturbance. The a-IGZO TFTs, metal-insulator-metal (MIM), and metalinsulator-semiconductor (MIS) capacitors with the SiCOH layer demonstrate reliable device performance, V th shifts, and capacitance changes with an increase in the gate bias stress. A exible device with SiCOH enables the suppression of abnormal V th 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.

Section: Electrical and Physical Characteristics Of The Mim And Mis Capacitormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Highly Reliable Flexible Device With Charge Compensation Layer

Khim

et al. 2022

Preprint

Self Cite

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.