Low power consumption is essential for wearable and internet-of-things applications. An effective way of reducing power consumption is to reduce the operation voltage using a very thin and high-dielectric gate insulator. In an oxide thin-film transistor (TFT), the channel layer is an oxide material in which oxygen reacts with metal to form a thin insulator layer. The interfacial oxidation between the gate metal and In–Ga–Zn oxide (IGZO) was investigated with Al, Ti, and Mo. Positive bias was applied to the gate metal for enhanced oxygen diffusion since the migration of oxygen is an important factor in interfacial oxidation. Through interfacial oxidation, a top-gate oxide TFT was developed with low source–drain voltages below 0.5 V and a gate voltage swing less than 1 V, which provide low power consumption.

A vertical oxide thin-film transistor was developed with interfacial oxidation for low voltage operation. The gate metal was used as a spacer for the definition of the transistor’s channel as well as the gate electrode. After definition of the vertical side wall, an IGZO (In-Ga-Zn Oxide) layer was deposited, followed by the interfacial oxidation to form a thin gate insulator. Ta was used for the gate material due to the low Gibbs free energy and high dielectric constant of tantalum oxide. A 15 nm tantalum oxide layer was obtained by the interfacial oxidation of Ta at 400 °C under oxygen atmosphere. The thin gate oxide made it possible to operate the transistor under 1 V. The low operation voltage enables low power consumption, which is essential for mobile application.

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Low voltage oxide thin-lm transistors (TFTs) operating below 1.0 V were developed using a high dielectric constant tantalum oxide produced by thermal oxidation. Thermal oxidation was carried out at 400, 500, and 600 °C under an oxygen atmosphere. The tantalum oxide was evaluated by X-ray photoelectron spectroscopy (XPS). XPS con rmed the binding energy of Ta4f, indicating the binding state of tantalum oxide. The bottom gate oxide TFT with the gate insulator of tantalum oxide grown at 500 °C exhibited mobility of 12.61 cm2/V and a threshold voltage of 0.46 V. The transfer characteristics at the drain voltages below 1.0 V show its applicability to low voltage operation below 1 V. The bootstrapped inverter with developed oxide TFTs operated well at the operation voltages of both the 1.0 and 2.0 V.

Liquid Crystal Display (LCD) and Organic Light Emitting Diode (OLED) display are operated by voltage or current driving. Several types of Thin-Film Transistor (TFT) are used in the backplane of a display, LTPS and a-IGZO TFTs are those. As the applied voltage increases to increase the brightness of the display, heat generation also increases at the channel of the TFT. Such heat generation increase the temperature, which degrades the characteristics of the TFT, and decrease the lifetime of the organic device. Therefore, in order to keep the quality of the display, it is necessary to monitor the temperature of the display and control related signals to implement optimal image quality. There are various temperature sensors which can be used to detect such a temperature change in a display. In the case of using a discrete temperature sensor, the process and cost are increased by attaching the temperature sensor additionally. However, in the case of a temperature sensor integrated into the display, an process for the temperature sensor is not necessary. One way to integrate is using resistance changing material with a reference resistor outside. In this case, temperature accuracy can be reduced when the reference resistance changes due to the influence of the external temperature. To solve the problem, external reference resistance is removed in this proposed sensor scheme. Figure 1 shows the developed thin-film temperature sensor, which consists of two wires connected in series. The temperature coefficients of Molybdenum (Mo) and Indium Tin Oxide (ITO) are different from each other, and that of ITO is about 1.2 times or more than that of Mo. In this scheme, no external resistance is required. In addition, to reduce the process steps, a thin film temperature sensor is designed to replace a light shield layer which is formed at the bottom of the active layer to prevent the input of light. The two thin film materials are connected in series and the voltages at a connecting point are measured. The generated heat transferred to the temperature sensor was tested for repeatability and accuracy. The thin-film temperature sensor was designed to be located at the bottom of a-IGZO Top Gate TFT structure to check the heating during the operation of TFT. an interlayer insulation film was deposited on the temperature sensor before deposition of the active layer. The temperature of the TFT was measured by a temperature sensor Figure 1. shows the schematic cross-sectional structure of the developed oxide TFT with an integrated temperature sensor. Figure 1