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Functional Inorganic Materials and Devices
Ultra-High Speed Intense Pulsed-Light Irradiation Technique for High-Performance Zinc Oxynitride Thin-Film Transistors Hyun-Jun Jeong, Hyun-Mo Lee, Chung Hyeon Ryu, Eun-Jae Park, Ki-Lim Han, Hyun-Jun Hwang, Kyung-Chul Ok, Hak-Sung Kim, and Jin-Seong Park ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b20291 • Publication Date (Web): 04 Jan 2019 Downloaded from http://pubs.acs.org on January 11, 2019
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ACS Applied Materials & Interfaces
Ultra-High Speed Intense Pulsed-Light Irradiation Technique for High-Performance Zinc Oxynitride Thin-Film Transistors Hyun-Jun Jeong‡1, Hyun-Mo Lee‡1, Chung-Hyeon Ryu‡2, Eun-Jae Park1, Ki-Lim Han1, Hyun-Jun Hwang2, Kyung-Chul Ok1, Hak-Sung Kim*,2,3, and Jin-Seong Park*,1 1Division
of Materials Science and Engineering, Hanyang University, 222, Wangsimni-ro,
Seongdong-gu, Seoul, 04763, Republic of Korea 2Department
of Mechanical Convergence Engineering, Hanyang University, 222,
Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea 3Institute
of Nano Science and Technology, Hanyang University, 222, Wangsimni-ro,
Seongdong-gu, Seoul, 04763, Republic of Korea
Abstract
In this study, we investigated the effects of intense pulsed light (IPL) on the electrical performance properties of zinc-oxynitride (ZnON) thin films and thin-film transistors (TFTs) with different irradiation energies. Using the IPL process on the
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oxide/oxynitride semiconductors has various advantages, such as ultra-short process time (~100 ms) and high electrical performance without any additional thermal processes. As the irradiation energy of IPL increased from 30 J/cm2 to 50 J/cm2, the carrier concentration of ZnON thin films decreased from 5.07 x 1019 cm-3 to 9.96 x 1016 cm-3 and the electrical performance of TFTs changed significantly, which is optimized at an energy of 40 J/cm2 (field effect mobility = 48.4 cm2/Vs). Not only the properties of TFTs, such as mobility, S.S., and hysteresis, but also the stability of the device under negative bias were degraded as irradiation energy increased. This degradation was contributed to the change of nitrogen-related bonding states, such as nonstoichiometric ZnxNy and N-N bonding, rather than that of oxygen-related bonding states and the atomic composition of ZnON thin films. Optimization of the IPL process in our results makes it possible to produce high performance ZnON TFTs very fast without any additional thermal treatment, which indicates that highly productive TFT fabrication is achievable with this process.
Keywords: zinc-oxynitride, thin-film transistor, high mobility, intense pulsed light (IPL), ultra-fast fabrication process,
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1
Introduction
In recent years, the emergence of new concept displays (e.g., flexible/stretchable displays, head-mount displays, augmented reality (AR), and virtual reality (VR)) made it possible for people to have new experiences. In particular, the AR/VR technique has already been used in various industries (e.g., games and real estate) and mixed reality (MR), which is a combination of AR and VR, allowing people to experience more abundant content. Since a low-resolution display can cause users to experience discomfort, such as dizziness, highresolution technologies are essential for these industries. Amorphous oxide semiconductor (AOS)-based thin-film transistors (TFTs) have been studied widely because of their various advantages, such as low process temperature (< 350oC), relatively high mobility (~10 cm2/Vs)1 and low off-current2 (less than 1 pA), compared to conventional hydrogenated amorphous silicon (a-Si) and polycrystalline silicon (p-Si)-based devices. The amorphous In-Ga-Zn-O (IGZO) semiconductor, which is the most popular among the AOS materials, has been widely used in various areas, such as channel layers of display backplanes3-7, optical/gas sensors8-10 and other electronic devices. Other AOS materials (In-Sn-Zn-O11, Al-In-Zn-Sn-O12, etc.13-16) have also been studied to improve electrical performance and stability relative to IGZO. Recently, zinc oxynitride (ZnON) has attracted attention as a promising material for electronic/optical devices owing to its high electronic performance (low electron effective mass, high field effective mobility over 50 cm2/Vs) and electrical stability under illumination conditions, such as low persistent photocurrent (PPC) originating from oxygen vacancies (Vo), compared to other oxide semiconductors17-18. Since the outstanding electrical performance and possibilities of ZnON devices was reported, various groups have been optimizing the device fabrication process and studying its other
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applications, such as photo-sensors19-24. Since the meta-stable Zn3N2 bonding has a larger enthalpy value than ZnO bonding (standard enthalpy of formation: ∆Hf0,Zn-N = - 26.2 kJ/mol, ∆Hf0,Zn-O = - 350 kJ/mol at 298 K), deposition and stabilizing processes to fabricate stable stoichiometric Zn3-N2 and ZnO bonding with high temperatures above 250oC were limited. For these reasons, our previous research was conducted with control of the various post-treatment conditions, such as temperature, time and ambient atmosphere. To fabricate highly stable ZnON semiconductors, long and complicated post-treatment processes were suggested to avoid the loss of nitrogen atoms and unstable nitrogen-related bonding in the thin film. Because these inefficient annealing processes are not suitable for the mass production of ZnON semiconductors for commercialization, new methods for rapid treatment techniques are needed. The IPL technique has been received the increased attention as an alternative to the conventional thermal annealing techniques. The IPL irradiation from xenon lamp, which emits radiation in the range between 350 and 950 nm, encompassing the entire visible spectrum is available to sinter the metal NPs because the plasmon resonance bands of metal nano-particles are in visible spectrum25-28. Also, it can immediately sinter the metal nano-particles within a few milliseconds at room temperature under ambient conditions. Furthermore, the operation of its process is very convenient owing to just several operation conditions with irradiation time, pulse gap, pulse energy and pulse number. Because of these benefits, IPL technique has been widely used in the fields of solution based printed electronics for nano-particles/nanowire sintering process29-32. We studied the effects of IPL treatment on the electrical performance and stability of ZnON TFTs and the relationship between the chemical bonding states with different photo
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energies. Stable ZnO and non-stoichiometric Zn3N2 bonding were formed without any phase or composition changes, which is attributed to degradation of mobility and bias stability as the photo energy increased. The ZnON TFTs with IPL treatment showed high electrical performance (saturation mobility (μsat) > 50 cm2/Vs) and bias stability (threshold voltage shift (ΔVth)
