Ultrathin flexible thin film transistors with CYTOP encapsulation by debonding process

Abstract

We fabricated ultrathin flexible thin film transistors with hydrophobic encapsulation layer by debonding process. In the debonding process, to separate the transistors from the carrier glass in deionized (DI) water, a strong hydrophobic material such as CYTOP was used for encapsulation, thus increasing their resistance to moisture. PVA was used as a release layer and the debonding process was optimized to separate the carrier glass and the transistors. It was confirmed that water penetration into the device can be suppressed effectively when the CYTOP thickness is 800 nm. In addition, the electrical characteristics remained almost constant even in the presence of water for 50 min. The total thickness after debonding process was approximately 2 μm. Waterproof experiments and debonding process were performed for a simple inverter circuit as well as a discrete device, and the operation and voltage gain of the inverter did not change when water was placed on the device or after debonding process. Finally, the flexibility was measured by transferring the device to a flexible PI substrate. Consequently, it was confirmed that degradation in the electrical properties was slightly up to a bending radius of 2.5 mm.

Improved Electrical and Temporal Stability of In-Zn Oxide Semiconductor Thin-Film Transistors With Organic Passivation Layer

“…These results indicate that the device stability was significantly affected by the type of the polymer passivation layer. Owing to the high hydrophobicity as shown by the high water contact angle, the CYTOP fluoropolymer is much more effective in protecting the active layer from ambient moisture than the slightly hydrophilic PMMA [42].…”

Vertically Integrated Electronics: New Opportunities from Emerging Materials and Devices

“…CYTOP is another fluoropolymer that can prevent potential damage to the underlying organic semiconductors because fluorinated solvents for CYTOP are generally orthogonal to organic semiconductors [ 58 , 59 ]. Combined with other advantages including excellent chemical stability and strong hydrophobicity, CYTOP has been used as a protective layer as well as a dielectric layer of top-gate geometry [ 60 – 63 ]. Kim et al [ 20 ] utilized the bilayer dielectric where the CYTOP layer was spin coated and Al 2 O 3 was deposited by atomic layer deposition (ALD) thereon (Fig.…”

Stability of organic thin-film transistors based on ultrathin films of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT)

“…Our choice of these materials was dictated by the requirement to deposit the encapsulation immediately (within one to two minutes) following the completion of the deposition of the ultrathin DNTT film in the same vacuum-deposition system and without breaking the vacuum. This ruled out virtually all popular organic-TFT-encapsulation materials, such as Al 2 O 3 , 45 Cytop 46 and parylene, 47 as none of these can be deposited in the vacuum-deposition system in which the DNTT films are deposited. The three materials we selected for the in-situ encapsulation of ultrathin DNTT films are polytetrafluoroethylene (PTFE), C 60 and titanyl phthalocyanine (TiOPc).…”