Chih-Wei Chien

High-Performance Flexible a-IGZO TFTs Adopting Stacked Electrodes and Transparent Polyimide-Based Nanocomposite Substrates

We demonstrated flexible amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) on fully transparent and high-temperature polyimide-based nanocomposite substrates. The flexible nanocomposite substrates were coated on the carrier glass substrates and were debonded after the TFT microfabrication. The adoption of the Ti/IZO stacked electrodes as source/drain/ gain electrodes significantly improved the etching compatibility with other material layers, enabling successful implementation of flexible a-IGZO TFTs onto the transparent nanocomposite substrates by conventional lithographic and etching processes. The flexible a-IGZO TFTs exhibited decent mobility and mechanical bending capability. Field-effect mobility of up to 15.9 cm2/V · s, a subthreshold swing of 0.4 V/dec, a threshold voltage of 0.8 V, and an on/off ratio of >; 108 were extracted from the TFT characteristics. The devices could be bent down to a radius of curvature of 3 mm and yet remained normally functional. Such successful demonstration of flexible oxide TFTs on transparent flexible substrates using fully lithographic and etching processes that are compatible with existing TFT fabrication technologies shall broaden their uses in flexible displays and electronics.

Self-Aligned Top-Gate Coplanar In-Ga-Zn-O Thin-Film Transistors

Self-aligned techniques are often used in conventional CMOS and Si-based thin-film transistors (TFTs) technologies due to various merits. In this paper, we report self-aligned coplanar top-gate InGaZnO TFTs using PECVD a-SiNinfin:H patterned to have low hydrogen content in the channel region and high hydrogen content in the source/drain region. After annealing to induce hydrogen diffusion from a-SiNinfin:H into the oxide semiconductor, the source-drain regions become more conductive and yet the channel region remains suitable for TFT operation, yielding a working self-aligned TFT structure. Such fabrication involves neither back-side exposure nor ion implantation, and thus may be compatible with the typical and cost-effective TFT manufacturing.

Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-IGZO Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates

In this paper, we had successfully implemented flexible top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin- film transistors (TFTs) on colorless and transparent polyimide (PI)-based nanocomposite substrates using fully lithographic and etching processes that are compatible with existing TFT mass fabrication technologies. The use of the selectively coated release layer between the nanocomposite PI film and the glass carrier ensured smooth debonding of the plastic substrate after TFT fabrication. The TFTs showed decent performances (with mobility >; 10 cm2/V · s) either as fabricated or as debonded from the carrier glass. By bending the devices to different radii of curvature (from a flat state to an outward bending radius of 5 mm), influences of mechanical strains on the characteristics of flexible a-IGZO TFTs were also investigated. In general, the mobility of the flexible a-IGZO TFT increased with the tensile strain, whereas the threshold voltage decreased with the tensile strain. The variation of the mobility in a-IGZO TFTs versus the strain appeared smaller than those observed for amorphous silicon TFTs.

Room-temperature-processed flexible n-InGaZnO/p-Cu2O heterojunction diodes and high-frequency diode rectifiers

In this work, we report successful implementation of room-temperature-processed flexible n-InGaZnO/p-Cu2O heterojunction diodes on polyethylene naphthalate (PEN) plastic substrates using the sputtering technique. Using n-type InGaZnO and p-type Cu2O films deposited by sputtering at room temperature, flexible n-InGaZnO/p-Cu2O heterojunction diodes were successfully fabricated on PEN plastic substrates. The didoes on PEN substrates exhibited a low apparent turn-on voltage of 0.44?V, a high rectification ratio of up to 3.4???104 at ?1.2?V, a high forward current of 1?A?cm?2 around 1?V and a decent ideality factor of 1.4, similar to the characteristics of n-InGaZnO/p-Cu2O diodes fabricated on glass substrates. The characterization of the frequency response of the room-temperature-processed flexible n-InGaZnO/p-Cu2O heterojunction diode rectifiers indicated that they are capable of high-frequency operation up to 27?MHz, sufficient for high-frequency (13.56?MHz) applications. Preliminary bending tests on diode characteristics and rectifier frequency responses indicate their promise for applications in flexible electronics.

Influence of channel-deposition conditions and gate insulators on performance and stability of top-gate IGZO transparent thin-film transistors

— Amorphous-oxide-semiconductor thin-film transistors (TFTs) have gained wide attention in recent years due to their many merits. In this paper, a series of top-gate transparent thin-film transistors (TFTs) based on amorphous-indium—gallium—zinc—oxide (a-IGZO) semiconductors have been fabricated and investigated. Specifically, low-temperature SiNx and SiOx were used as the gate insulator and different Ar/O2 gas-flow ratios were used for a-IGZO channel deposition to study the influences of gate insulators and channel-deposition conditions. In addition to the investigation of device performance, the stability of these TFTs was also examined by applying constant-current stressing. It was found that a high mobility of 30-45 cm2/V-sec and small threshold-voltage shift in constant-current stressing can be achieved using SiNx with suitable hydrogen-content stoichiometry as the gate insulator and the carefully adjusted Ar/O2 flow ratio for channel deposition. These results may be associated with hydrogen incorporation into the channel, the lower defect trap density, and the better water/oxygen barrier properties (impermeability) of the low-temperature SiNx.

Top-Gate Staggered a-IGZO TFTs Adopting the Bilayer Gate Insulator for Driving AMOLED

We report the successful implementation of top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with decent performance and environmental stability by adopting the SiOx/SiNx bilayer gate-insulator stack. The PECVD SiOx and SiNx were used as the first and second gate insulators, respectively, in the TFT to simultaneously ensure the channel/gate-insulator interface properties for device performances and the water impermeability of the gate insulator for effective passivation of the channel layer. It was also found that the cleanliness of the back-channel interface (and thus the effectiveness of the source/drain etching process) is critical for the successful implementation of the top-gate staggered a-IGZO TFTs. In this paper, a two-step wet-etching process for source/drain was used to ensure the quality of the back-channel interface. Finally, we successfully integrated the top-gate staggered a-IGZO TFTs into a working 2.2-in active matrix organic light-emitting display panel, demonstrating the real use of the developed TFTs.

High-performance oxide TFTs based on solution-processed ZTO

Thin-film transistors (TFTs) based on solution-processed Zinc-Tin oxides (ZTO) of different Zn:Sn compositions are investigated. The solution-processed ZTO TFTs show rather high device performances, with the mobility up to 15 cm2/V-s, the on/off ratio up to 106~107 and a subthreshold slope <;0.6 V/decade.

61.4: High‐Performance and Highly Rollable a‐IGZO TFTs Adopting Composite Electrodes and Transparent Polyimide Substrates

We have demonstrated high-performance and highly rollable flexible oxide TFTs on fully transparent/colorless polyimide substrates by adopting lithographic and etching processes and composite electrodes. The TFTs exhibited a field-effect mobility of up to 15.9 cm2/Vs, a sub-threshold swing of 0.43 V/decade, and an on/off ratio of > 108. The devices could be bent down to a radius of 3 mm and yet remained normally functional.

P‐34: Influences of Channel Deposition Conditions on Characteristics of Bottom‐Gate Oxide TFTs Adopting In‐Free Zinc‐Tin Oxides

Bottom-gate Zinc-Tin oxide (ZTO, ZnO: SnO2) thin film transistors were fabricated on glass substrates with fully photolithographic/etching processes and with completed passivation. The TFTs exhibit a field-effect mobility of up to 12.1 cm2/V-s and an on/off ratio of >107.