Sih Lee

Improvement in the bias stability of amorphous indium gallium zinc oxide thin-film transistors using an O2 plasma-treated insulator

The effects of an O2 plasma-treated SiNX-based insulator on the interfacial property and the device performances of amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) were investigated. We tried to improve the interfacial characteristics by reducing the trap density between the SiNX gate insulator and a-IGZO channel by the O2 plasma treatment. The plasma treated-device performances were remarkably improved. The drastic improvements obtained for the O2 plasma-treated a-IGZO TFTs included excellent bias stability as well as a high field effect mobility (μFE) of 19.4 cm2/V s, an on/off current (ION/IOFF) of 108, and a subthreshold value (S) of 0.5 V/decade.

Application of DC Magnetron Sputtering to Deposition of InGaZnO Films for Thin Film Transistor Devices

This is the first report demonstrating that InGaZnO (IGZO) thin films deposited using DC magnetron sputtering can be used for the active channel layer of a thin film transistor (TFT) device. We have determined the process conditions at which dc magnetron sputtering provides a high growth rate and smooth surface for IGZO thin films using an InGaZnO4 ceramic target. The effect of the oxygen content on the electrical properties of the IGZO thin films was examined. The field effect mobility of the TFT device fabricated with the IGZO thin film deposited at an optimum oxygen partial pressure of 6% was 9.2 cm2 V-1 s-1. The operation mechanism of IGZO-TFT was explained on the basis of the band diagram with flat band voltage. Moreover, we evaluated the effects of bias stress on transistor performance and showed that device instability appears to be a result of the carrier trapping and releasing in the gate insulator layer under high gate voltage stress.

Nanoscale floating-gate characteristics of colloidal Au nanoparticles electrostatically assembled on Si nanowires

Nanoscale floating-gate characteristics of colloidal Au nanoparticles electrostatically assembled on Si nanowires have been investigated. Colloidal Au nanoparticles with ∼5nm diameters were selectively deposited onto the lithographically defined n-type Si nanowire surface by 2min electrophoresis between the channel and the side gates. The device transfer characteristics measured at room temperature showed hysteresis, with the depletion mode cutoff voltage applied by the side gates shifted by as much as 1.5V, with the source-drain bias at 1.4V. The results demonstrate that the electrostatic assembly of colloidal Au nanoparticles is a useful method for the fabrication of Si nanowire based nanoscale floating-gate nonvolatile memory structures.

Amorphous Indium Gallium Zinc Oxide Semiconductor Thin Film Transistors Using O2 Plasma Treatment on the SiNx Gate Insulator

In this study, we investigated the role of processing parameters on the electrical characteristics of amorphous In–Ga–Zn–O (a-IGZO) thin film transistors (TFTs) fabricated using DC magnetron sputtering at room temperature. Processing parameters including the oxygen partial pressure, annealing temperature, and channel thickness have a great influence on TFT performance and better devices are obtained at a low oxygen partial pressure, annealing at 200 °C, and a low channel thickness. We attempted to improve the a-IGZO TFT performance and stability under a gate bias stress using O2 plasma treatment. With an O2 plasma treated gate insulator, remarkable properties including excellent bias stability as well as a field effect mobility (µFE) of 11.5 cm2 V-1 s-1, a subthreshold swing (S) of 0.59 V/decade, a turn-on voltage (VON) of -1.3 V, and an on/off current ratio (ION/IOFF) of 105 were achieved.

Effects of oxygen contents in the active channel layer on electrical characteristics of ZnO-based thin film transistors

The authors report the fabrication and characteristics of thin film transistors with ZnO channel layers (ZnO TFTs) having different oxygen contents. Also, the authors define the operation mechanism of ZnO TFTs as the variation of oxygen contents in the ZnO channel layer. The ZnO thin films were deposited on SiO2∕n-Si substrate by dc magnetron sputtering at various oxygen partial pressures. Effects of oxygen contents in ZnO thin films on the electrical performance of ZnO TFTs with bottom gate structure were investigated. The ZnO thin films deposited at oxygen partial pressures of 40% exhibit a nonstoichiometric system in an oxygen rich state, resulting in resistivity as high as 105Ωcm. ZnO TFTs with this channel layer exhibited depletion mode, turn on voltage of −15V, on-off current ratio of ∼106, and field effect mobility of 0.88cm2∕Vs. This research implied that an attractive application for TFTs involves their use as select transistors in individual pixels of an active-matrix liquid-crystal display.

Phosphorus Doping Effect in a Zinc Oxide Channel Layer to Improve the Performance of Oxide Thin-Film Transistors

In this study, we fabricated phosphorus-doped zinc oxide-based thin-film transistors (TFTs) using direct current (DC) magnetron sputtering at a relatively low temperature of 100°C. To improve the TFT device performance, including field-effect mobility and bias stress stability, phosphorus dopants were employed to suppress the generation of intrinsic defects in the ZnO-based semiconductor. The positive and negative bias stress stabilities were dramatically improved by introducing the phosphorus dopants, which could prevent turn-on voltage (VON) shift in the TFTs caused by charge trapping within the active channel layer. The study showed that phosphorus doping in ZnO was an effective method to control the electrical properties of the active channel layers and improve the bias stress stability of oxide-based TFTs.