Tochigi, Japan
Tochigi, Japan

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Shishido H.,Semiconductor Energy Laboratory Co. | Amano S.,Semiconductor Energy Laboratory Co. | Toyotaka K.,Semiconductor Energy Laboratory Co. | Miyake H.,Semiconductor Energy Laboratory Co. | And 8 more authors.
49th Annual SID Symposium, Seminar, and Exhibition 2011, Display Week 2011 | Year: 2011

We prototyped a 6.0-in. color sequential XGA LCD using an oxide semiconductor. A color sequential LCD has lower power consumption than a color filter LCD because light use efficiency is better. We utilize the low I off of the oxide semiconductor and make frame rate lower, which leads to the lower power consumption of drivers. The color sequential LCD can have a monochrome electronic paper function with a white backlight on.


Hirakata Y.,Semiconductor Energy Laboratory Co. | Kubota D.,Semiconductor Energy Laboratory Co. | Yamashita A.,Semiconductor Energy Laboratory Co. | Miyake H.,Semiconductor Energy Laboratory Co. | And 8 more authors.
49th Annual SID Symposium, Seminar, and Exhibition 2011, Display Week 2011 | Year: 2011

We have fabricated a prototype of a field-sequential blue phase mode LCD having an integrated scan driver including an oxide semiconductor FET. By using the blue phase mode, the frame rate of 180 fps (a subframe frequency of 540 Hz) or higher is now available. We obtained favorable images without color breakup.


Yamazaki S.,Semiconductor Energy Laboratory Co. | Atsumi T.,Semiconductor Energy Laboratory Co. | Dairiki K.,Semiconductor Energy Laboratory Co. | Okazaki K.,Advanced Film Device Inc. | Kimizuka N.,University of Sonora
ECS Journal of Solid State Science and Technology | Year: 2014

It is revealed that c-axis aligned crystal In-Ga-Zn oxide (CAAC-IGZO) and nanocrystalline IGZO films have high-density crystalline morphologies (5.9-6.3 g/cm3) and are very stable under electron-beam irradiation in transmission electron microscope observation. The electrical properties are suitable for practical use. We attempted to reproduce a previously reported amorphous IGZO film with no ordering. However, we were not able to confirm its existence; rather, we found nanocrystals with a width of 1-3 nm and a thickness of 0.7-0.8 nm. Furthermore, it is apparent that the amorphous-like film has low density (higher than or equal to 5.0 g/cm3 and lower than 5.9 g/cm3), and thus is an unstable material in which nanocrystals change when subjected to electron-beam irradiation. We fabricated field-effect transistors using CAAC-IGZO and examined their switching characteristics. As a result of microfabrication scaling, cutoff frequencies of 2 GHz and 1.5 GHz were obtained when the channel lengths were 60 nm and 100 nm, respectively. Switching characteristics in the order of GHz were obtained by microfabrication scaling with a field effect mobility of 5-10 cm2/V s, which opens new possibilities for oxide semiconductor large-scale integration. © 2014 The Electrochemical Society. All rights reserved.


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.


Amano S.,Semiconductor Energy Laboratory Co. | Harada H.,Semiconductor Energy Laboratory Co. | Akimoto K.,Semiconductor Energy Laboratory Co. | Sakata J.,Semiconductor Energy Laboratory Co. | And 8 more authors.
48th Annual SID Symposium, Seminar, and Exhibition 2010, Display Week 2010 | Year: 2010

By using an oxide semiconductor, we successfully prototyped a 3.4-inch QHD LCD panel including data and scan drivers: their power consumption is reduced by variable frame frequency (from 1/60 fps to 120 fps) depending on images. Low frame frequency in displaying still images on a PC monitor can reduce eyestrain.


Amano S.,Semiconductor Energy Laboratory Co. | Miyake H.,Semiconductor Energy Laboratory Co. | Nishi T.,Semiconductor Energy Laboratory Co. | Hirakata Y.,Semiconductor Energy Laboratory Co. | And 4 more authors.
ECS Transactions | Year: 2011

An oxide semiconductor thin film transistor (TFT) has much higher mobility than an amorphous silicon (a-Si) TFT, which leads to realization of larger displays with higher defimtion. Moreover, it has much lower off leak current than the a-Si TFT. We have focused on this feature and successfully fabricated a low-power 6.0-inch extended graphics array (XGA) transmissive liquid crystal display (LCD) with source and scan drivers integrated on a glass substrate. In order to realize low power consumption, unnecessary rewriting is not performed at the time of still image display. The interval between rewrite operations in our panel could be extended to about 1 min (= 1/60 fps) at the time of displaying still images. The power consumption of the drivers at 1/60 fps can be about 1/3,600 of that at 60 fps. We also discuss burn-in and flickers, which might be observed when this driving method is applied. ©The Electrochemical Society.


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.


Nakashima M.,Semiconductor Energy Laboratory Co. | Oota M.,Semiconductor Energy Laboratory Co. | Ishihara N.,Semiconductor Energy Laboratory Co. | Nonaka Y.,Semiconductor Energy Laboratory Co. | And 6 more authors.
Journal of Applied Physics | Year: 2014

To clarify the origin of the major donor states in indium gallium zinc oxide (IGZO), we report measurement results and an analysis of several physical properties of IGZO thin films. Specifically, the concentration of H atoms and O vacancies (VO), carrier concentration, and conductivity are investigated by hard X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, thermal desorption spectroscopy, and Hall effect measurements. The results of these experiments suggest that the origin of major donor states is H occupancy of VO sites. Furthermore, we use first-principles calculations to investigate the influence of the coexistence of VO and H in crystalline InGaO3(ZnO)m (m-1). The results indicate that when H is trapped in VO, a stable complex is created that serves as a shallow-level donor. © 2014 AIP Publishing LLC.


Hirakata Y.,Semiconductor Energy Laboratory Co. | Kubota D.,Semiconductor Energy Laboratory Co. | Yamashita A.,Semiconductor Energy Laboratory Co. | Ishitani T.,Semiconductor Energy Laboratory Co. | And 7 more authors.
Journal of the Society for Information Display | Year: 2012

Through the realization of a blue-phase-mode (hereinafter, the operational mode of liquid crystal having a blue phase is referred to as a blue-phase mode), a display using an improved fieldsequential method was confirmed to be capable of display at a frame rate of 180 fps (field frequency of 540 Hz) or higher. Under this condition, an image without annoyance caused by color breakup was obtained. Moreover, a novel field-sequential AMLCD integrated with a scan driver by combining the liquid-crystal-display (LCD) technology using blue phase and oxide-semiconductor technology has been developed. © Copyright 2012 Society for Information Display.


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.

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