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Tochigi, Japan

Hirohashi T.,Semiconductor Energy Laboratory Co. | Okazaki K.,Advanced Film Device Inc. | Yamazaki S.,Semiconductor Energy Laboratory Co.
Japanese Journal of Applied Physics | Year: 2014

Crystallization of In-Ga-Zn-O (IGZO) thin films by electron-beam irradiation when observed with a transmission electron microscope (TEM) has been reported. Hence in this study, we have investigated deposition conditions and properties of films that could be easily crystallized in TEM observation. In a film deposited under high pressure, voids are observed, and such a film has high impurity concentration and is crystallized by electron-beam irradiation in TEM observation. In contrast, a dense film deposited under low pressure is not crystallized by electron-beam irradiation. Moreover, from a thin film transistor (TFT) fabricated using a film that can potentially be crystallized by electron-beam irradiation, normal characteristics cannot be obtained. However, by using a dense film, a TFT with less variation in characteristics can be fabricated. © 2014 The Japan Society of Applied Physics. Source


Yamazaki S.,Semiconductor Energy Laboratory Co. | Suzawa H.,Semiconductor Energy Laboratory Co. | Inoue K.,Semiconductor Energy Laboratory Co. | Kato K.,Semiconductor Energy Laboratory Co. | And 3 more authors.
Japanese Journal of Applied Physics | Year: 2014

We report, in this paper, that crystalline In-Ga-Zn-oxide (IGZO) can be formed over an amorphous surface or over an uneven surface by a sputtering process at lower than 500°C through the purification of IGZO. Crystalline IGZO, in which no clear grain boundary is observed, shows caxis alignment but random a- and b-axis orientations without alignment. This crystal morphology differs from other morphologies that have been known thus far, such as single crystal and polycrystal morphologies. Our model for understanding the formation of this crystal morphology [c-axisaligned crystal (CAAC)] is also discussed. Upon thermal annealing of a deposited film at lower than 500°C, nanocrystal regions remaining in the CAAC can be converted into the CAAC structure. Accordingly, Ioff can be at the yA/μm (10-24A/μm) level at 85°C. It has been proven that by utilizing normally-off characteristics even with L/W = 40nm/40nm (actual size: L/W = 68nm/34 nm), the fabrication of a three-dimensional (3D) LSI with a 3D oxide semiconductor/Si hybrid structure is feasible. © 2014 The Japan Society of Applied Physics. Source


Niikura Y.,Semiconductor Energy Laboratory Co. | Kubota D.,Semiconductor Energy Laboratory Co. | Hatsumi R.,Semiconductor Energy Laboratory Co. | Hirakata Y.,Semiconductor Energy Laboratory Co. | And 4 more authors.
Journal of the Society for Information Display | Year: 2016

As usage time for portable electronic terminals increases, associated problems regarding such extended use (e.g., battery holding times and eyestrain) are highlighted. Within the domain of power saving, we previously developed an idling stop (IDS) driving that avoids unnecessary refresh. Moreover, for reducing eyestrain to the highest extent possible, we calculated a luminance change in IDS driving that is not perceived as flickering by humans, via the use of a temporal modulation transfer function. According to the results of such calculations, a liquid crystal mixture that suppresses luminance changes perceived by humans was hence constructed. With the combined use of the liquid crystal mixture and a c-axis-aligned crystal oxide semiconductor with low off-state leakage current, a display could be developed wherein leakage current in IDS driving could be significantly reduced, along with enjoyed benefits of prolonged refresh intervals and power savings. The subject display is very eye-friendly, with less flickering than comparable technologies. © Copyright 2016 Society for Information Display. Source


Yamazaki S.,Semiconductor Energy Laboratory Co. | Hirohashi T.,Semiconductor Energy Laboratory Co. | Takahashi M.,Semiconductor Energy Laboratory Co. | Adachi S.,Semiconductor Energy Laboratory Co. | And 8 more authors.
Journal of the Society for Information Display | Year: 2014

Our crystalline In-Ga-Zn oxide (IGZO) thin film has a c-axis-aligned crystal (CAAC) structure and maintains crystallinity even on an amorphous base layer. Although the crystal has c-axis alignment, its a-axis and b-axis have random arrangement; moreover, a clear grain boundary is not observed. We fabricated a back-channel-etched thin-film transistor (TFT) using the CAAC-IGZO film. Using the CAAC-IGZO film, more stable TFT characteristics, even with a short channel length, can be obtained, and the instability of the back channel, which is one of the biggest problems of IGZO TFTs, is solved. As a result, we improved the process of manufacturing back-channel-etched TFTs. © Copyright 2014 Society for Information Display. Source


Hatsumi R.,Semiconductor Energy Laboratory Co. | Fukai S.,Semiconductor Energy Laboratory Co. | Kubota Y.,Semiconductor Energy Laboratory Co. | Yamashita A.,Semiconductor Energy Laboratory Co. | And 10 more authors.
Journal of the Society for Information Display | Year: 2013

In order to reduce eye strain, a driving method for reducing flickers of liquid crystal display (LCD) is devised. For this driving, an oxide semiconductor (OS) is used in a backplane, liquid crystal and alignment layer materials are optimized, and a fringe field switching (FFS) mode with a structurally formed storage capacitor is used. This work reveals that suitable usages of positive and negative liquid crystals differ from each other according to their characteristics. This work also describes an OS-LCD with a touch sensor we fabricated for mobile devices, which proves the possibility of reducing-eye-strain technology (REST) with reduced flickers. © Copyright 2014 Society for Information Display. Source

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