Wednesday, April 17, 2019

NCD’s ALD IGZO TFTs exhibit remarkable stabilities

NCD Co., Ltd, a global equipment and technology provider of ALD (Atomic Layer Deposition), has developed oxide Thin Film Transistors (TFTs) using In-Ga-Zn-O (IGZO) channels.

IGZO oxide TFTs have rapidly been increased interest in these days, as LTPO oxide TFTs have been adapted for state of the art displays like apple watches as well as IGZO is the most applicable for future transparent flexible devices due to its high mobility and optical transparency. However, IGZO thin films are required to meet the various properties such as higher resolution, large-area uniformity, and better device stability with ultra-thin and flexible structures. Atomic layer deposition (ALD) has recently been reported as a replacement for the conventional sputtering method for fabricating IGZO thin films. The sputtering deposition has some problems such as uniformity issues in thickness and composition, degradation of properties by plasma damages and non-uniformity in the magnetic field, and stability issue of the sputtering target. While ALD-IGZO could show film thickness and composition control in atomic scale, high film conformity and excellent thickness uniformity on large area substrates because ALD is dominated by a self-limiting growth mechanism.

Figure 1: (a) Structure of IGZO TFT and microscopic cross-sectional view of IGZO TFT by Lucida GD Series ALD

Figure 2: a) Comparisons of the IDS–VGS transfer characteristics and IGS gate leakage currents between the devices using ALD IGZO channels with thicknesses of 6 and 10 nm. (b) IDS–VDS output characteristics for the TFT using 6 nm-thick IGZO channel.(*)

NCD has developed oxide TFTs using very thin In-Ga-Zn-O channels, and the excellent device characteristics and the reliable bias temperature stabilities can be successfully obtained. Such a remarkable device stabilities of TFTs with the IGZO channel prepared by the ALD process can help extend the employment of IGZO TFTs for various applications.(*)

NCD’s Lucida GD Series ALD which can run up to 6th generation substrates (1500x1850mm2) could be the best ALD coating solutions for IGZO channels since it’s very compatible, reliable, and producible on large area applications. NCD could provide the most advanced ALD-IGZO technology with its technological knowledge and experience to the customers who are seeking competitive ALD-IGZO systems for current LTPO applications or large-area OLED displays as well as for future flexible transparent displays.

Figure 3: Lucida™ GD Series ALD

* RSC Adv., 2018, 8, 25014, Investigations on the bias temperature stabilities of oxide thin film transistors using In–Ga–Zn–O channels prepared by atomic layer deposition, So-Jung Yoon, Nak-Jin Seong, Kyujeong Choi, Woong-Chul Shin, and Sung-Min Yoon. DOI: 10.1039/c8ra03639j

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