Performance Of a-IGZO Thin-film Transistors Research Articles

Role of in-situ hydrogen plasma treatment on gate bias stability and performance of a-IGZO thin-film transistors

This work investigates the effect of an in situ hydrogen plasma treatment on gate bias stability and performance of amorphous InGaZnO thin-film transistors (TFTs) deposited by using atmospheric-pressure PECVD. The H2 plasma-treated a-IGZO channel has shown significant improvement in bias stress induced instability with a minuscule threshold voltage shift (ΔV th) of 0.31 and −0.17 V under positive gate bias stress (PBS) and negative gate bias stress (NBS), respectively. With the aid of the energy band diagram, the proposed work demonstrates the formation of negative species O2 − and positive species H2O+ in the backchannel under PBS and NBS in addition to ionized oxygen vacancy (Vo) defects at a-IGZO/ZrO2 interfaces are the reason for gate bias instability which could be effectively suppressed with in situ H2 plasma treatment. From the experimental result, it is observed that the electrical performance such as field-effect mobility (μ FE), on-off current ratio (I on/I off), and subthreshold swing improved significantly by in situ H2 plasma treatment with passivation of interface trap density and bulk trap defects.

Fabrication and Characterization of a-IGZO Thin-Film Transistors With and Without Passivation Layers

The thin-film transistors (TFTs) devices based on amorphous indium gallium zinc oxide (a-InGaZnO, a-IGZO) films were fabricated and characterized in this paper. We have employed the a-IGZO thin film as an active channel layer in the bottom gate structure of transistor, the silicon dioxide (SiO2) as a gate insulator, and the indium tin oxide (ITO) as a gate source and drain electrodes. All of them were grown on ITO glass substrates by radio frequency (RF) magnetron sputtering technique. However, there were still some inherent defects in the a-IGZO materials, it would be affected the performance of the fabricated transistors. Therefore, in this work, it explored to research a-IGZO TFTs with aluminum (Al) passivation layers as sensitive to water and oxygen thereby affect the device stability, and time dependence threshold voltage variation in ambient of passivation layer and reliability. Demonstrably, our experimental results revealed that the W/L (W = wide, L = length) ratio is 10, the on/off ration and the mobility would be better, respectively. Moreover, the results also showed improvement in the performance of a-IGZO TFTs with the Al passivation layers and annealing process treatment.

The Effect of Microwave Annealing of Reliability Characteristics on Amorphous IGZO Thin Film Transistors.

Amorphous oxide semiconductors (AOSs) are attracted much attention due to high mobility, low temperature deposition, flexible, transmission, and uniformity. The thin film transistors (TFTs) with a-IGZO thin film as active layer perform higher field-effect mobility (>10 cm²/V·S), larger Ion/Ioff ratio (106), smaller subthreshold swing and better stability against electrical stress. LaAlO₃/ZrO₂ is employed as gate electrode and gate dielectric layer for a-IGZO TFTs, under the premise that performance of a-IGZO TFTs without decreasing. Due to the good selectivity of energy transformation and rapid heating rate, microwave annealing is applied to improve the device reliability in the investigation. With adjusting the parameter of microwave annealing, the effect on reliability characteristics of a-IGZO TFTs is studied.

Simulation of the influence of the gate dielectric on amorphous indium-gallium-zinc oxide thin-film transistor reliability

Indium-gallium-zinc oxide (IGZO) thin films have attracted significant attention for application in thin-film transistors (TFTs) due to their specific characteristics, such as high mobility and transparency. The performance of a-IGZO TFTs with four different insulators (SiO2 Si3N4, Al2O3 and HfO2) is examined using a numerical simulator (Silvaco Atlas). It is found that the output performance is significantly enhanced with high relative permittivity of the insulator. HfO2 gives the best performance: lower threshold voltage 0.23 V and subthreshold 0.09 V dec−1, higher field-effect mobility 13.73 cm2 s−1 V−1 and on current (Ion) and Ion/Ioff ratio $$2.81 \times 10^{ - 6}$$ A, $$5.06 \times 10^{12}$$ , respectively. Therefore, HfO2 gate showed high stability compared with other gate insulator materials.

Effects of Stacked Mo–Ti/Cu Source and Drain Electrodes on the Performance of Amorphous In–Ga–Zn-O Thin-Film Transistors

In this letter, the performance of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) is investigated using the stacked Mo-Ti/Cu source (S) and drain (D) electrodes. The test samples A and B of the a-IGZO TFT have interlayers with Mo/Ti ratios of 2.29 and 1.15, respectively, for the SD electrodes, and each has a core layer of Cu stacked on the top of the interlayers. They were fabricated and measured to compare their performance in terms of the transfer characteristic and mobility. The measurement results showed that the sample B with a lower Mo/Ti ratio exhibited better performance than the sample A: higher field-effect mobility by 4.4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V-s, higher saturation mobility by 3.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V-s, smaller sub-threshold slope by 0.91 V/decade, and lower threshold voltage by 1.4 V. In addition, the material properties of samples A and B were obtained using the line scan of the energy dispersive spectroscopy and analyzed with technology computer-aided design simulation. As a result, the performance of a-IGZO TFTs can be optimized by tuning the Mo/Ti ratios of the interlayer in the stacked SD electrodes.

Enhanced performance of a-IGZO thin-film transistors by forming AZO/IGZO heterojunction source/drain contacts

A low-cost Al-doped ZnO (AZO) thin film was deposited by radio-frequency magnetron sputtering with different Ar/O2 flow ratios. The optical and electrical properties of an AZO film were investigated. A highly conductive AZO film was inserted between the amorphous InGaZnO (a-IGZO) channel and the metal Al electrode to form a heterojunction source/drain contact, and bottom-gate amorphous a-IGZO thin-film transistors (TFTs) with a high κ HfON gate dielectric were fabricated. The AZO film reduced the source/drain contact resistivity down to 79 Ω cm. Enhanced device performance of a-IGZO TFT with Al/AZO bi-layer S/D electrodes (W/L = 500/40 µm) was achieved with a saturation mobility of 13.7 cm2 V−1 s−1, a threshold voltage of 0.6 V, an on-off current ratio of 4.7 × 106, and a subthreshold gate voltage swing of 0.25 V dec−1. It demonstrated the potential application of the AZO film as a promising S/D contact material for the fabrication of the high performance TFTs.

Systematic investigation on the effect of contact resistance on the performance of a‐IGZO thin‐film transistors with various geometries of electrodes

AbstractWe demonstrate the influence of the contact resistance on the electrical properties of a‐IGZO thin‐film transistors (TFTs) with ZrO2 gate insulator grown by rf‐magnetron sputtering at room temperature by adopting various channel widths and lengths. These TFTs have all been processed at room temperature with the same channel W/L ratio (W/L = 5) but different channel widths (50, 150, 250, and 350 µm). As the channel width increases from 50 to 350 µm, the on‐current and field effect mobility increase from 0.7 to 1 mA and 19 to 31 cm2/V s, respectively. However, the subthreshold swing decreases from 0.37 to 0.19 V/decade. These results show that the contact resistance strongly affects the device performances and should be considered in these applications.

Effect of Excimer Laser Annealing on the Performance of Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors

This article reports a method for reducing the contact resistance between amorphous-InGaZnO (a-IGZO) channel and source/drain layer via XeCl excimer laser annealing (ELA) and the device performance of a-IGZO thin-film transistors (TFTs) in terms of laser energy density. The source/drain region in the a-IGZO layer was selectively ELA-treated using a mask, and the resistivity dramatically reduced compared to that of the untreated film (from 10 4 to 10 ―3 Ω cm). Our TFTs had a field-effect mobility of 21.7 cm 2 /V s, an on/off ratio of 1.2 × 10 8 , a threshold voltage of ―0.15 V, and a subthreshold swing of 0.26 V/decade.