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High Mobility, High Stability Oxide Semiconductor TFT
AS oxide semiconductors with a mobility of 10 cm2/V·s were reported, they began attracting widespread attention as semiconductor materials that can replace amorphous silicon. In particular, oxide semiconductor thin-film transistors (oxide TFTs) have been extensively studied as display driving components and have recently succeeded in mass production for mobile devices. Moreover, several studies have utilized the extremely low off-current and back-end-of-line (BEOL) compatibility of oxide semiconductors to develop memory devices, such as dynamic random-access memory (DRAM) and NAND flash memory. However, higher mobility is still required for various applications of oxide semiconductors.
[1] S. -I. Cho et al. "Inserting Interfacial Layer for Atomic-Scaled Hydrogen Control to Enhance Electrical Properties of InZnO TFTs", IEEE Electron Device Letters, 2023
Trench Structure TFT
Oxide thin-film transistors (TFTs) with high mobility that exceed 100 cm2/V·s and appropriate turn-on voltage (Von) are necessary to drive next-generation displays and memory devices. However, a trade-off relationship exists between mobility and Von, making it difficult to achieve both in the same oxide TFT. In this letter, we propose a buffer layer engineered trench-TFT (T-TFT) as a solution to this trade-off problem. Trench TFT shows a high mobility of 129 cm2/V·s and a suitable Von of −0.4 V.
Channel-Shortening Effect (CSE) in oxide thin film transistors (TFTs) is a crucial issue that must be resolved for applications in ultra-high-resolution displays. One of the origins of the CSE is the diffusion of a shallow donor such as hydrogen from other layers into the channel. In this study, we investigated for the first time the CSE of self-aligned Al-doped In-Sn-Zn-O (Al-ITZO) TFTs with planar and trench structure.
[1] Y. Im et al. "C Buffer Layer Engineering of Indium Oxide Based Trench TFT for Ultra High Current Driving", IEEE Electron Device Letters, 2023
[2] J. Kim et al. "Channel-Shortening Effect Suppression of a High-Mobility Self-Aligned Oxide TFT using Trench Structure", IEEE Electron Device Letters, 2021
Self-Aligned TFT
Top-gate self-aligned structured oxide thin-film transistors (TFTs) are suitable for the backplanes of high-end displays because of their low parasitic capacitances. The gate insulator (GI) deposition process should be carefully designed to manufacture a highly stable, high-mobility oxide TFT, particularly for a top-gate structure. In this study, a nanometer-thick Al2O3 layer via plasma-enhanced atomic layer deposition (PE-ALD) is deposited on the top-gate bottom-contact structured oxide TFT as the interface tailoring layer, which can also act as the hydrogen barrier to modulate carrier generation from hydrogen incorporation into the active layer of the TFT during the following process such as post-annealing.
[1] J. B. Ko et al. "Engineering a sub-nanometer interface tailoring layer for precise hydrogen incorporation and defect passivation for high-end oxide thin-film transistors", ACS Applied Materials & Interfaces, 2023
Flexible and deformable Thin Film Transistor
Thin-film transistors (TFTs) are utilized as the backplane devices for active matrix (AM) liquid-crystal displays, AM organic light-emitting diode (AMOLED) displays, AM-LEDs, and quantum-dot LEDs. TFTs with amorphous oxide semiconductors are suitable candidates for such applications owing to their multiple advantages such as ease of fabrication, high electron mobility, high electrical stability, and uniformity over a large area. Therefore, it is necessary to develop flexible and transparent oxide TFTs that exhibit outstanding electrical performances. Furthermore, it is essential to design ultrathin display devices to ensure their complete coverage on and attachment to various objects including stretchable substrates.
[1] J. B. Ko et al. "Ultrathin, Flexible, and Transparent Oxide Thin-FIlm Transistors by Delamination and Transfer methods for Deformable DIsplays", Adv Mater Tech, 2021
Thin Film Encapsulation
Organic light emitting diode (OLED) is attracting attention as a light emitting technology to realize flexible display because of low price, low power consumption, and vivid color. OLED is composed of anode, organic emitting material and cathode. Each component is deteriorated when exposed to water and oxygen, making it difficult to use for a long time. Therefore, it is essential to develop a thin film encapsulation technology that effectively blocks the external environment for long-term use in OLED-based mobile and TV. We are currently focusing on nitride, alumina-based thin film encapsulation technology that is thin and high-performance for barrier.
[1] K. W. Park et al. "High-Performance Thin H:SiON OLED Encapsulation Layer Deposited by PECVD at Low Temperature", RSC Adv, 2019
[2] J. Kim et al. "Effect of H2 Addition during PECVD on the Moisture Barrier Property and Environmental Stability of Thin H:SiNx Passivation Film", Journal of American Ceramic Society, 2021
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