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Won-Ju Cho

Bio: Won-Ju Cho is an academic researcher from Kwangwoon University. The author has contributed to research in topics: Thin-film transistor & Non-volatile memory. The author has an hindex of 25, co-authored 277 publications receiving 2358 citations. Previous affiliations of Won-Ju Cho include Electronics and Telecommunications Research Institute.


Papers
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Journal ArticleDOI
TL;DR: In this paper, an ultrathin HfO2 trap layer with a thickness of 2 nm stored almost the same charges with the Si3N4 layer with thickness of 7 nm.
Abstract: MHOS (metal-HfO2–SiO2–Si) structure capacitors were fabricated to investigate the charge trapping properties of HfO2 layer with various thicknesses for the applications of charge trap flash (CTF) memory devices. Also, the centroid of charge trap in HfO2 layer was extracted by constant current stress method and compared with that of conventional Si3N4 layer. The gate leakage current of MHOS capacitor due to tunneling was significantly reduced by stacking the HfO2 trap layer on thin SiO2 tunnel layer. The MHOS capacitors showed a larger memory window than the MNOS (metal-Si3N4–SiO2–Si) capacitors at the same trap layer thickness, because the HfO2 layer has better charge trapping efficiency than the Si3N4 layer. It is found that ultrathin HfO2 trap layer with a thickness of 2 nm stored almost the same charges with Si3N4 layer with a thickness of 7 nm. Consequently, the application of ultrathin HfO2 to charge storage layer can considerably improve the performance and enhance the high density of CTF memory.

118 citations

Journal ArticleDOI
TL;DR: The UTB DGISFET will allow the ISFET-based biosensor platform to continue enhancement into the next decade and provide a comprehensive analysis of the body thickness effects especially how the thick body can render the degradation in the device performance, such as sensitivity and stability.
Abstract: Recently, thin-film transistor based-ISFETs with the dual-gate (DG) structures have been proposed, in order to beat the Nernst response of the standard ISFET, utilizing diverse organic or inorganic materials. The immutable Nernst response can be dramatically transformed to an ultra-sensing margin, with the capacitive-coupling arisen from the DG structure. In order to advance this platform, we here embedded the ultra-thin body (UTB) into the DG ISFET. The UTB of 4.3 nm serves to not only increase its sensitivity, but also to strongly suppress the leakage components, leading to a better stability of the DG ISFET. In addition, we first provide a comprehensive analysis of the body thickness effects especially how the thick body can render the degradation in the device performance, such as sensitivity and stability. The UTB DG ISFET will allow the ISFET-based biosensor platform to continue enhancement into the next decade.

83 citations

Journal ArticleDOI
TL;DR: In this article, a linear relation was observed between the threshold voltage shift when the temperature varies from −150 to 150°C and the number of the interface states present within the energy range of 0.2 −0.4 eV from the conduction band edge energy.
Abstract: Temperature dependence of threshold voltage in n-channel SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) was studied. Linear relation was observed between the threshold voltage shift when the temperature varies from −150 to 150 °C and the number of the interface states present within the energy range of 0.2–0.4 eV from the conduction band edge energy Ec. This relationship revealed that the interface state profile near Ec in n-channel SiC MOSFETs can be represented by that in n-type SiC MOS capacitors. The relationship between the channel mobility and the interface state profile also suggested that the interface states within the energy range of 0.2–0.4 eV from Ec have little influence on the channel mobility.

74 citations

Journal ArticleDOI
TL;DR: In this paper, an ensemble of Si nanowires (NWs) was integrated into an electrolyte-insulator-semiconductor (EIS) sensor with a large capacitance, near-Nernst-limit pH sensitivity, and good reliability.
Abstract: a b s t r a c t Low sensitivity and poor reliability currently limit the applications of solid-state bio-chemical sensors. We demonstrate an electrolyte-insulator-semiconductor (EIS) sensor with a large capacitance, near- Nernst-limit pH sensitivity, and good reliability by integrating an ensemble of Si nanowires (NWs) for the first time. The NWs were fabricated by using the electroless wet etching technique. An Al2O3/SiO2 bilayer coating was employed as a sensing membrane. The EIS sensors with 3.8 m long NWs exhibited about 8 times larger capacitance than that of a planar type EIS sensors that were fabricated using the same fabrication scheme without integrating NWs. The measured pH sensitivity at room temperature was 60.2 mV/pH, which is higher than the theoretical Nernstian of 59 mV/pH. Our results and analysis clearly indicate that ultra-sensitive pH sensing can be realized with optimized NW integrated EIS sensors.

66 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated novel patterning techniques to produce ultrafine patterns for nanoscale devices, such as triple-gate metal oxide semiconductor field effect transistor (MOSFET) with a gate length of 6nm.
Abstract: We investigated novel patterning techniques to produce ultrafine patterns for nanoscale devices. Hydrogen silsesquioxane (HSQ) was employed as a high-resolution negative tone inorganic electron beam resist. The nanoscale patterns with sub-10nm linewidth were successfully formed. A trimming process of HSQ by the reactive ion etcher (RIE) played an important role for the formation of 5nm nanowire patterns. Additionally, hybrid lithography was used to produce various device patterns as well as to minimize proximity effects of electron beam lithography (EBL). Finally, we successfully fabricated triple-gate metal oxide semiconductor field effect transistor (MOSFET) with a gate length of 6nm by using the proposed patterning process.

65 citations


Cited by
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Patent
01 Aug 2008
TL;DR: In this article, the oxide semiconductor film has at least a crystallized region in a channel region, which is defined as a region of interest (ROI) for a semiconductor device.
Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

1,501 citations

Journal ArticleDOI
TL;DR: This review focuses on the fundamentals of flexible pressure sensors, and subsequently on several critical concepts for the exploration of functional materials and optimization of sensing devices toward practical applications.
Abstract: By virtue of their wide applications in personal electronic devices and industrial monitoring, pressure sensors are attractive candidates for promoting the advancement of science and technology in modern society. Flexible pressure sensors based on organic materials, which combine unique advantages of flexibility and low-cost, have emerged as a highly active field due to their promising applications in artificial intelligence systems and wearable health care devices. In this review, we focus on the fundamentals of flexible pressure sensors, and subsequently on several critical concepts for the exploration of functional materials and optimization of sensing devices toward practical applications. Perspectives on self-powered, transparent and implantable pressure sensing devices are also examined to highlight the development directions in this exciting research field.

940 citations

Journal ArticleDOI
TL;DR: The UWBG semiconductor materials, such as high Al‐content AlGaN, diamond and Ga2O3, advanced in maturity to the point where realizing some of their tantalizing advantages is a relatively near‐term possibility.
Abstract: J. Y. Tsao,* S. Chowdhury, M. A. Hollis,* D. Jena, N. M. Johnson, K. A. Jones, R. J. Kaplar,* S. Rajan, C. G. Van de Walle, E. Bellotti, C. L. Chua, R. Collazo, M. E. Coltrin, J. A. Cooper, K. R. Evans, S. Graham, T. A. Grotjohn, E. R. Heller, M. Higashiwaki, M. S. Islam, P. W. Juodawlkis, M. A. Khan, A. D. Koehler, J. H. Leach, U. K. Mishra, R. J. Nemanich, R. C. N. Pilawa-Podgurski, J. B. Shealy, Z. Sitar, M. J. Tadjer, A. F. Witulski, M. Wraback, and J. A. Simmons

785 citations

Journal ArticleDOI
TL;DR: To imitate tactile sensing via e‐skins, flexible and stretchable pressure sensor arrays are constructed based on different transduction mechanisms and structural designs that can map pressure with high resolution and rapid response beyond that of human perception.
Abstract: The skin is the largest organ of the human body and can sense pressure, temperature, and other complex environmental stimuli or conditions. The mimicry of human skin's sensory ability via electronics is a topic of innovative research that could find broad applications in robotics, artificial intelligence, and human-machine interfaces, all of which promote the development of electronic skin (e-skin). To imitate tactile sensing via e-skins, flexible and stretchable pressure sensor arrays are constructed based on different transduction mechanisms and structural designs. These arrays can map pressure with high resolution and rapid response beyond that of human perception. Multi-modal force sensing, temperature, and humidity detection, as well as self-healing abilities are also exploited for multi-functional e-skins. Other recent progress in this field includes the integration with high-density flexible circuits for signal processing, the combination with wireless technology for convenient sensing and energy/data transfer, and the development of self-powered e-skins. Future opportunities lie in the fabrication of highly intelligent e-skins that can sense and respond to variations in the external environment. The rapidly increasing innovations in this area will be important to the scientific community and to the future of human life.

679 citations