Abstract
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.
Highlights
A vertical oxide thin-film transistor was developed with interfacial oxidation for low voltage operation
Amorphous silicon Thin-film transistors (TFTs) were applied to liquid crystal displays (LCDs), and low-temperature polycrystalline silicon TFTs were adopted in high-resolution LCDs and organic light emitting diode (OLED) displays
The first interlayer dielectric (ILD) of SiO2 and metal gate electrode were deposited by successive sputtering, and dry etched at one time with one photo mask
Summary
A vertical oxide thin-film transistor was developed with interfacial oxidation for low voltage operation. Since a TFT has a metal–insulator–metal (MIS) structure, effective ways to reduce the operation voltage are decreasing the thickness of the gate insulator and using a high dielectric-constant material. Both the decrease of the thickness and increase of the dielectric constant increase the induced charge in the channel by the gate voltage, which results in a decrease of the threshold voltage of the TFT and enables the low voltage operation of the TFT. Interfacial oxidation between a gate metal and an IGZO layer was used instead of vacuum deposition for the gate insulator, which is the first try to the oxide vertical TFT and remove the deposition process and reduce plasma induced deterioration of the layer during plasma process
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