Effect of the Electrode Materials on the Drain-Bias Stress Instabilities of In–Ga–Zn–O Thin-Film Transistors

Abstract

The effects of electrode materials on the device stabilities of In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) were investigated under gate- and/or drain-bias stress conditions. The fabricated IGZO TFTs with a top-gate bottom-contact structure exhibited very similar transfer characteristics between the devices using indium-tin oxide (ITO) and titanium electrodes. Typical values of the mobility and threshold voltage of each device were obtained as 13.4 cm(2) V(-1) s(-1) and 0.72 V (ITO device) and 13.8 cm(2) V(-1) s(-1) and 0.66 V (titanium device). Even though the stabilities examined under negative and positive gate-bias stresses showed no degradation for both devices, the instabilities caused by the drain-bias stress were significantly dependent on the types of electrode materials. The negative shifts of the threshold voltage for the ITO and titanium devices after the 10(4)-s-long drain-bias stress were estimated as 2.06 and 0.96 V, respectively. Superior characteristics of the device using titanium electrodes after a higher temperature annealing process were suggested to originate from the formation of a self-limiting barrier layer at interfaces by nanoscale observations using transmission electron microscopy.

Microwave Annealing Effect for Highly Reliable Biosensor: Dual-Gate Ion-Sensitive Field-Effect Transistor Using Amorphous InGaZnO Thin-Film Transistor

“…18,19 However, before using an a-IGZO TFT as a biosensor, the problem of threshold voltage instability of the TFT must be resolved. 20,21 For biosensor applications, this instability is one of the most critical considerations because it directly affects the reliability of the biosensors. To overcome this problem and achieve satisfactory performance and stability of the device, use of the high-temperature thermal annealing process at ∼600°C is typically required.…”

Effects of Deposition Temperature on the Device Characteristics of Oxide Thin-Film Transistors Using In–Ga–Zn–O Active Channels Prepared by Atomic-Layer Deposition

“…Next, the NBIS of the devices were also investigated with varying the irradiation wavelengths. Under the negative-bias stress in dark conditions, the IGZO TFTs generally exhibit stable device characteristics owing to the n-type semiconducting nature of IGZO channel layer. − Contrarily, the V TH values of the IGZO TFTs might experience considerable amounts of negative shifts under the NBIS conditions, which is related to the fact that the donor states can be newly created in shallow levels and provide conduction electrons into the conduction bands. , Sometimes, the generated conduction electrons can also be trapped at the interface between the gate insulator and IGZO channel layers. The NBIS tests were performed under the light illuminations by using the light-emitting diodes with the wavelengths of 635 (red), 530 (green), and 470 nm (blue) corresponding to the energies of 1.95, 2.34, and 2.65 eV.…”

Origin of Degradation Phenomenon under Drain Bias Stress for Oxide Thin Film Transistors using IGZO and IGO Channel Layers

“…From this series of evaluations of the transfer characteristics, it was confirmed that the IGO-TFT exhibited excellent DBS stability compared to those of the IGZO-TFT. From our previous reported work9, the effects of electrode materials on the device stabilities under DBS condition were investigated. Via nanoscale TEM images and EDS analysis, we could found that the Ti device annealed at a higher temperature exhibited an enhanced stability under the DBS due to the synergy effects of robust interface and role of transition layer acting as a barrier contrary to the severely degraded ITO device after the DBS.…”

“…Additionally, the interface damaged by the ion bombardment during the channel deposition process could be suggested to accelerate undesirable interdiffusion, even though it would have minor impact1314. This DBS-driven interdiffusion might induce some compositional changes at the interface close to the drain electrode9. The carrier concentration at specified regions near the drain electrode happened to increase by the compositional change and/or atomic rearrangement.…”

“…From our previous report9, the choice of electrode materials was found to be key in securing the reliability of In-Ga-Zn-O (IGZO) TFTs under DBS. However, a detailed degradation mechanism for long-term device reliability under the DBS was not clearly established.…”