Device Performance and Reliability Characterization of Interface and Bulk Effect in Amorphous Indium Gallium Zinc Oxide
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1108-A09-12
Device Performance and Reliability Characterization of Interface and Bulk Effect in Amorphous Indium Gallium Zinc Oxide (a-IGZO) Thin Film Transistor. Kwang-il Choi1, Dong-Ho Nam1, Sung-Soo Park1, Jae-Kyeong Jeong2, and Ga-Won Lee1 1 Department of Electronic Engineering, Chungnam National Univ., Daejeon 305-764, Korea, Republic of 2 Corporate R&D Center, Samsung SDI Co., LTD, 428-5, Yongin-Si, Gyeonggi-Do 449-902, Korea, Republic of ABSTRACT We have investigated the relation of device performance and reliability characteristic on the a-IGZO TFTs fabricated by the different channel deposition conditions. Specific conditions of RF and DC sputtering are described as follows; magnetron power density of (1.4 W/cm2)/(2.0 W/cm2) in Ar/O2 gas ratio of (65/35)/(72/28), and the entire gas pressure was (5.0 mTorr ) and (3.4 mTorr), respectively. In transfer characteristic curve of the each fabricated device, electrical characteristic of DC device was more superior to RF one. And the results of C-V characteristic depending on frequency showed that RF device has bad channel quality. However, threshold voltage degradation on the normalized gate bias stress and C-V hysteresis characteristic mean that DC device is worse than RF one about the interface characteristic. From these results, we can know that electrical characteristic is more affected by channel traps than interface characteristic and the device showing superior electrical characteristic doesn`t guarantee good reliability invariably. And this result may be related with high magnetron power density in DC sputtered device. INTRODUCTION Recently, active matrix organic light emitting diode (AMOLED) have attracted considerable attentions than active matrix liquid crystal displays (AMLCDs) as a next generation flat panel display (FPD) because they are even faster, lighter and thinner than AMLCDs [1-2]. Conventional thin film transistors such as amorphous Si thin film transistor (a-Si TFTs) which are used as driving circuit for AMLCDs have the advantage of uniformity and low fabrication cost. However a-Si TFTs may be insufficient to drive large area AMOLEDs because of their low mobility and unstable reliability characteristic. Also, polycrystalline Si thin film transistor (polySi TFTs) which are used as a backplane for AMOLED displays due to their high mobility and stability, suffer from the non-uniformity of their mobility and threshold voltage, due to the presence of grain boundaries. Due to these reasons, amorphous Indium Gallium Zinc Oxide (aIGZO) thin film transistor (TFT) is in the limelight of a promising candidate for an alternative to poly-Si TFTs and a-Si TFTs, because they provide better uniformity in terms of their important device parameter such as threshold voltage and On/Off current ratio [3-4]. Furthermore, high channel mobility (>10cm2/V-s) is attainable with these devices even in the amorphous phase [5]. Therefore a-IGZO TFTs have been extensively studied by various groups. However, there is little report on interface and bulk effect on device per
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