InGaZnO Thin Film Research Articles

Hydrogen behavior and microstructural evolution in flexible IGZO thin films under stress

In this study, we investigated the effect of mechanical stress on hydrogen diffusion in flexible amorphous InGaZnO (a-IGZO) thin films and the resulting microstructural changes. The cyclic bending test under different curvature radii (R) revealed significant morphological evolution and bond state changes in IGZO thin films. As the curvature radius decreases from 20 mm to 5 mm, the surface of the sample gradually becomes rough and cracks appear. Simultaneously, changes in nanoscale topological structure and chemical composition exhibit stronger hydrogen diffusion and structural relaxation: The oxygen-hydrogen (O-H) bond content increased from 19 % to 55 %, while the metal-oxygen (M − O) bond content decreased from 50 % to 28 %. The M − H content increased, and In-H related structures underwent transformation. The radius of gyration (Rg) increasing from 1.652 nm to 1.812 nm. These results provide quantitative insights into the stability and performance of IGZO-based flexible electronic devices under mechanical deformation.

Plasma Etch of IGZO Thin Film and IGZO/SiO2 Interface Diffusion in Inductively Coupled CH4/Ar Plasmas

ABSTRACTIn this work, the etching characteristics of InGaZnO4 (IGZO) thin films were systemically investigated in inductively coupled CH4/Ar plasmas with various gas ratios, bias voltages, and surface temperatures. The ion flux in the CH4/Ar plasmas was analyzed using bias power and voltage, whereas the relative densities of CH and H radicals were quantified through optical actinometry. The change in CH3 radical density was also estimated based on plasma kinetics analysis. The correlations between the plasma properties and IGZO etch rate were investigated. In CH4/Ar plasmas with CH4 ratios below 80%, the IGZO etch rate increases with a higher CH4 proportion, aligning with the ascending trend of CH3 radical density, which suggests that CH3 radical density acts as a limiting factor (radical‐limited regime). However, the IGZO etch rate decreases when the CH4 ratio exceeds 80%, corresponding to the reduction in ion flux, which indicates that ion flux becomes a limiting factor in this ion‐limited regime. The IGZO etch rate shows a linear relationship with bias voltage and follows the Arrhenius equation with varying surface temperature in plasmas without bias voltage. A spontaneous etch model was proposed based on these relationships. In this model, the IGZO etch rate depends on CH3 radical density and IGZO surface reactivity, where ion bombardment contributes more significantly to surface reactivity than high surface temperature. IGZO thin film was deposited on SiO2 during the fabrication of a 3D stacked ferroelectric field‐effect transistor (FeFET) memory device. The interaction between IGZO and SiO2 during CH4/Ar plasma processing was investigated using time‐of‐flight secondary ion mass spectrometry. The efficacy of removing IGZO atoms that had diffused into the SiO2 network was enhanced when subjected to plasma with a bias voltage, compared to the process without a bias voltage. However, exposure to CH4/Ar plasma resulted in a deeper diffusion of IGZO atoms into the SiO2 network, primarily attributed to ion bombardment rather than elevated surface temperature. A significant improvement in surface smoothness was achieved after IGZO and SiO2 etch by introducing BCl3 into the SiO2 etching chemistry.

DC and AC Performance of InGaZnO Thin-Film Transistors on Flexible PEEK Substrate

DC and AC Performance of InGaZnO Thin-Film Transistors on Flexible PEEK Substrate

Effect of Oxygen Plasma Treatment on the Performance of GQDs-Modulated InGaZnO Thin-Film Transistors

Effect of Oxygen Plasma Treatment on the Performance of GQDs-Modulated InGaZnO Thin-Film Transistors

Deposition time dependent structural and optical properties of polycrystalline [formula omitted] films

Sputtering-derived InGaZnO4 (IGZO) thin films were grown on quartz substrates and undergone post-deposition annealing at 700 °C for 2hr in N2 ambient. The influence of deposition time or film thickness on the morphological, structural and optical properties of polycrystalline IGZO thin films has been systematically investigated by means of characterization from field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectrophotometer. Results of AFM have shown that the root-mean-square (RMS) surface roughness of the IGZO films increases from 0.888 to 2.640 nm as the deposition time is extended from 50 to 250min. Analysis of XRD indicates that all the films are in polycrystalline phase, with crystallites growing into larger size accordingly to increasing deposition time. Appealingly and scarcely ever reported, the XRD diffraction planes can be separated into three domains, such as (0 0 l), (1 0 l) and (1 1 l) with different growth thicknesses. Optical measurement suggests that the optical bandgap have redshifted from 3.55 to 3.31eV at longer deposition time. Related mechanics about the change in physical properties against deposition time have been elaborated in detail. The validity of Swanepoel method, 1983 in deriving the refractive index of thick IGZO films has also been discussed.

Rational Design of Different Ga Content Bilayer InGaZnO Thin-Film Transistors With Al₂O₃/HfO₂ Passivation Layer

Rational Design of Different Ga Content Bilayer InGaZnO Thin-Film Transistors With Al₂O₃/HfO₂ Passivation Layer

Enhancing Reliability of Short-Channel Dual Gate InGaZnO Thin Film Transistors by Bottom-Gate Oxide Engineering

Enhancing Reliability of Short-Channel Dual Gate InGaZnO Thin Film Transistors by Bottom-Gate Oxide Engineering

Control of Interfacial Defect States in the Flexible InGaZnO Thin Film Transistor with a 6FDA-MDA Gate Insulator by Using an Al2O3 Interlayer

Control of Interfacial Defect States in the Flexible InGaZnO Thin Film Transistor with a 6FDA-MDA Gate Insulator by Using an Al₂O₃ Interlayer

Bi-directional threshold voltage shift of amorphous InGaZnO thin film transistors under alternating bias stress

Amorphous InGaZnO (a-IGZO) has attracted a lot of attention as a high-mobility channel material for thin film transistors (TFTs). However, the instability mechanism involving threshold voltage and subthreshold swing (SS) in a-IGZO TFTs still requires further investigation. In this study, we investigated the electrical instability of amorphous InGaZnO TFTs subjected to alternating positive and negative bias stresses. Based on the respective mechanisms under positive and negative bias stresses, including ionization and spatial movement of oxygen vacancies, bi-directional threshold voltage shifts were observed under alternating bias stress. The SS values vary with the bias stress polarity, reflecting the presence and distribution of oxygen vacancies. Our findings reveal a complementary mechanism based on oxygen vacancies, elucidating the behavior under complex bias stress schemes and extending our understanding of instability mechanisms beyond monotonous bias stress.

Reduction of internal stress in InGaZnO (IGZO) thin film transistors by ultra-thin metal oxide layer

In this study, the modification of indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) with an ultrathin metal oxide layer successfully reduces internal film stress. The introduction of an Al2O3 metal oxide layer effectively diminishes defects within the film and minimizes distortion in the film densification process. A low-temperature annealing process at 200 °C was employed to mitigate thermal expansion differences between the film and the substrate, thus reducing internal stress within the device. Furthermore, we have discovered that this structural modification holds the potential to enhance mechanical stress resistance. This paper offers a novel perspective and an experimental foundation for the stress analysis of flexible TFTs.

The Endurance and Reliability Mechanisms Investigation of InGaZnO and InSnO Thin Film Transistors

The Endurance and Reliability Mechanisms Investigation of InGaZnO and InSnO Thin Film Transistors

Increased Threshold Voltage of Amorphous InGaZnO Thin-Film Transistors After Negative Bias Illumination Stress

Increased Threshold Voltage of Amorphous InGaZnO Thin-Film Transistors After Negative Bias Illumination Stress

Ultrasonic Treatment-Induced Enhancement of Mechanical and Electrical Properties in InGaZnO Thin-Film Transistors

Ultrasonic Treatment-Induced Enhancement of Mechanical and Electrical Properties in InGaZnO Thin-Film Transistors

Self-Aligned InGaZnO Thin-Film Transistors and Circuits on Transparent Thin Glass and FEP Film

Self-Aligned InGaZnO Thin-Film Transistors and Circuits on Transparent Thin Glass and FEP Film

Control of hydrogen concentration on InGaZnO thin film using cryopumping system

Amorphous InGaZnO thin film transistors (a-IGZO TFTs) have been extensively studied as driving transistors for large organic light emitting diode (OLED) displays due to its’ exceptional uniformity. However, the positive bias stability (PBS) of a-IGZO TFT is not sufficiently acceptable to endure the long on-stress time. Here, the effect of hydrogen impurities in a-IGZO channels on the stability and performance of TFTs used in OLED displays are investigated. The hydrogen content in the a-IGZO film is reduced to limit the formation of trapping sites for charge carriers and improve TFT stability. This study uses a cryogenic pumping system to reduce the hydrogen impurity density during the deposition process and examines the electrical characteristics of bottom-gate a-IGZO TFTs. The threshold voltage shift (ΔVth) of the a-IGZO TFT fabricated using the cryogenic pumping system was found to be reduced by 3.4–6.9 V, compared to the TFT fabricated using the turbo molecular pump system. The hydrogen and oxygen concentrations in the oxide thin films are quantitatively analyzed, and the mechanism of OH bonding acting as an electron trap during positive bias stress is explained. Overall, this study provides insights into the impact of hydrogen impurities in a-IGZO TFT stability and performance, as well as proposes a method using cryopump for reducing hydrogen impurities to improve OLED display reliability.

Low temperature plasma deposited SiO2/organosilicon stacked film for transparent gate dielectric of InGaZnO thin film transistor

In this article, a 5-pair SiO2/organosilicon stacked film fabricated by inductively coupled plasma-enhanced chemical vapor deposition from hexamethyldisiloxane /O2 at low temperature was introduced as InGaZnO thin film transistor (IGZO TFT) gate dielectric for transparent flexible displays. The dielectric film has the flexibility of organosilicon while maintaining the high dielectric strength of SiO2. Due to the introduction of organosilicon, which connects with the IGZO active layer, the deep-state electron traps formed by oxygen vacancies are reduced, and moderate hydrogen diffused into IGZO layer becomes a shallow donor. Under the premise of high transmittance of the dielectric film, a high-performance TFT with mobility of 15.60 cm2/Vs was obtained.

Solution-Processed Aluminum-Zirconium Oxide as a Gate Dielectric for InGaZnO Thin Film Transistors

Solution-Processed Aluminum-Zirconium Oxide as a Gate Dielectric for InGaZnO Thin Film Transistors

Comprehensive investigation of sputtering deposition pressure effects on a-InGaZnO Schottky diodes

The effects of Ar sputtering deposition pressure on the optical, structural, morphological, and electrical properties of amorphous InGaZnO thin films were investigated. The InGaZnO thin films, which have amorphous structures determined by grazing incidence x-ray diffraction, contained In, Ga, Zn, and O confirmed by secondary ion mass spectrometry method. Additionally, when the thicknesses of the deposited thin films are examined, it was seen that the profilometer measurement results of the crater formed by secondary ion mass spectrometer and scanning electron microscope measurement results are nearly similar, and it is approximately 100 nm. The surface roughness, obtained from Atomic Force Microscopy results, show that decreased up to a particular value with the increase of the working pressure, and then the surface roughness increased. The optical band gaps of the films were obtained in the range of 3.50 eV−3.58 eV via Tauc relation by using the Ultraviolet-Visible measurements carried out in the wavelength range of 200 nm−1100 nm. It was seen that the optical band gap was decreased with the increase in Ar pressure. The electrical properties of InGaZnO thin film-based Schottky diodes, such as the barrier height, ideality factor, saturation current, series resistance, and shunt resistance, have also been studied comprehensively. The electrical results showed that diode properties change with increasing deposition pressure.

Improved reliability of a-IGZO thin-film transistor under positive gate bias stress by utilizing NH3 plasma treatment

In this paper, the degradation mechanisms of the bottom-gate amorphous InGaZnO thin film transistors (a-IGZO TFTs) under positive gate bias stress (PBS) are investigated. The PBS-induced degradation can be attributed to the electron capture at the interface of the gate insulator and a-IGZO and the generation of oxygen interstitial defects (Oi) in a-IGZO. The oxygen interstitial defect density (NOi) can be calculated by the degradation of SS during recovery after PBS. It is found that the proportion of degradation caused by Oi increases with the increased a-IGZO thickness. By utilizing NH3 plasma treatment, the threshold voltage shift was reduced by >40 % under PBS (@VG = 5 V, t = 1000s). Further analysis shows that NH3 plasma treatment can effectively suppress the electron capture at the interface and the generation of Oi during PBS. Thus, PBS reliability of a-IGZO TFTs is improved by the proposed method.

Low-Cost and High-Performance, Back-Channel Etched InGaZnO Thin Film Transistors by Spray Pyrolysis

Low-Cost and High-Performance, Back-Channel Etched InGaZnO Thin Film Transistors by Spray Pyrolysis