Chur-Shyang Fuh

Ambient Stability Enhancement of Thin-Film Transistor With InGaZnO Capped With InGaZnO:N Bilayer Stack Channel Layers

A thin-film transistor (TFT) with bilayer stack structure of amorphous nitrogenated InGaZnO (IGZO) (a-IGZO:N) on an IGZO channel is proposed to enhance device stability. The a-IGZO:N acting as a back-channel passivation (BCP) is formed sequentially just after the sputter-deposited amorphous IGZO (a-IGZO) film with in situ nitrogen incorporation process. The a-IGZO:N can effectively prevent the a-IGZO channel from exposing to the atmosphere and retarding interactions with ambient oxygen species. Also, the optical energy bandgap of the a-IGZO:N film is decreased due to the addition of nitrogen. This causes the a-IGZO TFT with a-IGZO:N BCP to exhibit high immunity to the ultraviolet-radiation impact.

Effect of Annealing on Defect Elimination for High Mobility Amorphous Indium-Zinc-Tin-Oxide Thin-Film Transistor

This letter studies the correlation of postannealing treatment on the electrical performance of amorphous In-Zn-Sn-O thin-film transistor (a-IZTO TFT). The 400 °C annealed a-IZTO TFT exhibits a superior performance with field-effect mobility of 39.6 cm²/Vs, threshold voltage (Vth) of -2.8 V, and subthreshold swing of 0.25 V/decade. Owing to the structural relaxation by 400 °C annealing, both trap states of a-IZTO film and the interface trap states at the a-IZTO/SiO₂ interface decrease to 2.16×10¹⁷ cm^-3eV^-1 and 4.38×10¹² cm^-2 eV^-1, respectively. The positive bias stability of 400 °C annealed a-IZTO TFTs is also effectively improved with a V_th shift of 0.92 V.

High-gain complementary inverter with InGaZnO/pentacene hybrid ambipolar thin film transistors

Ambipolar thin film transistors (TFTs) with InGaZnO/pentacene heterostructure channels are demonstrated for a high-voltage-gain complementary metal oxide semiconductor (CMOS) inverter. The ambipolar TFT exhibits a electron mobility of 23.8 cm2/V s and hole mobility of 0.15 cm2/V s for the InGaZnO and pentacene, respectively. The thermal annealing process was also studied to adjust electron concentration reducing operating voltage of the CMOS inverter. The voltage gain achieves as high as 60 obtained in the first and third quadrants of the voltage transfer characteristic. The high performance and simple manufacture of the heterostructure CMOS inverter show promise as critical components in various electrical applications.

Enhancement of reliability and stability for transparent amorphous indium-zinc-tin-oxide thin film transistors

We studied the influence of the backchannel passivation layer (BPL) on the ambient stability of amorphous indium-zinc-tin-oxide thin-film transistors (a-IZTO TFTs), in which atomic layer deposited (ALD) Al2O3 films and plasma-enhanced chemical vapor deposited (PECVD) SiO2 films were separately used to be the channel passivation layers. It was observed that the BPL deposition process strongly affects device performance and stability. From the results of the extracted activation energy (Eact), the Al2O3 passivation layer can reduce the trap density in localized tail states, which improves the mobility of a-IZTO TFTs. Compared with the SiO2 passivation layer, the Al2O3 passivation process effectively suppresses H injection into the a-IZTO channel layer underneath with secondary ion mass spectrometer analysis. In addition, it is found that the a-IZTO TFT with the Al2O3 passivation layer can enhance resistance against negative bias illumination stress (NBIS), making it reliable for realistic operation in flat panel displays.

Effects of Nitrogen on Amorphous Nitrogenated InGaZnO (a-IGZO:N) Thin Film Transistors

In this study, the role of nitrogen in the dc-sputtered amorphous indium gallium zinc oxide (a-IGZO):N are explored extensively with a series of nitrogen gas flow rates during IGZO film deposition. The amorphous film structure and the evolution of chemical bondings were confirmed by X-ray diffractometer and X-ray photoelectron spectroscopy spectra analysis. Also, electrical performance and reliability of a-IGZO:N thin-film transistors (TFTs) formed with different nitrogen gas flow rates were analyzed to study the effects of nitrogen on TFT devices. The device performance of a-IGZO:N TFTs can be enhanced with a proper nitrogen doping concentration. However, with excess nitrogen incorporation in the a-IGZO:N channel layer, both electric characteristic and reliability are degraded due to the extra creation of oxygen deficiencies in a-IGZO:N film and easy formation of unstable interface between gate insulator and channel layer, which were confirmed by low-frequency noise measurement. This potential issue of a-IGZO:N TFT characteristics can be effectively released by introducing a post-treatment on the surface of gate dielectric layer. The optimized electrical characteristics of a-IGZO:N TFT can exhibit a carrier mobility of 19.21 cm2/V·s, subthreshold swing of 0. 26 V/decade and threshold voltage (Vth) of -0.74 V in this study.

P‐64: Using Electroless Plating Technology for Copper Metallization in AMLCD Application

The feasibility of using electro-less plating (ELP) technology to manufacture copper (Cu) gate electrodes in TFTs is investigated. The poor adhesion between Cu and glass substrates is overcome by introducing ELP nickel-phosphorus layers. Self-aligning characteristics also omits the Cu-etching process. The similar electrical performance verifies the compatibility of this technology.