Stability and high-frequency operation of amorphous In-Ga-Zn-O thin-film transistors with various passivation layers
Stability and high-frequency operation of amorphous In-Ga-Zn-O thin-film transistors with various passivation layers
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DOI：
10.1016/j.tsf.2011.10.068
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发表时间：
2012-03-01
期刊：
影响因子：
2.1
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Nomura, Kenji;Kamiya, Toshio;Hosono, Hideo
研究了非晶In-Ga-Zn-O（a-IGZO）薄膜晶体管（TFT）的稳定性，重点研究了钝化层材料（Y2 O3、Al 2 O3、HfO 2和SiO2）和热退火对TFT稳定性的影响。检测了正偏压恒流应力（CCS）、无光照负偏压应力（NBS）和负偏压光照应力（NBLS）。发现如果沟道在钝化形成之前退火（沉积后退火）并且钝化层在>= 250 ℃下退火（制造后退火），则在所有稳定性测试方面，Y2 O3是本研究中最好的钝化层材料。制造后的Y2 O3钝化层的热退火产生非常稳定的TFT对CCS和NBS应力和消除subgap photoresponse高达2.9 eV的光子能量。即使对于具有2.7eV光子的NBLS，在3小时的测试之后，阈值电压偏移也被很好地抑制到-4.4V。这些结果提供了以下信息：（i）钝化去除了a-IGZO中的表面深亚带隙缺陷并消除了亚带隙光响应，但是（ii）在钝化过程之前应当去除a-IGZO中的体缺陷。Y2 O3钝化的TFT不仅在这些应力条件下稳定，而且还与高频操作兼容，电流增益截止频率为91 kHz，这与静态特性一致。(C)2011 Elsevier B. V.保留所有权利。
The stability of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) was investigated focusing on the effects of passivation layer materials (Y2O3, Al2O3, HfO2, and SiO2) and thermal annealing. Positive bias constant current stress (CCS), negative bias stress without light illumination (NBS), and negative bias light illumination stress (NBLS) were examined. It was found that Y2O3 was the best passivation layer material in this study in terms of all the stability tests if the channel was annealed prior to the passivation formation (post-deposition annealing) and the passivation layer was annealed at >= 250 degrees C (post-fabrication annealing). Post-fabrication thermal annealing of the Y2O3 passivation layer produced very stable TFTs against the CCS and NBS stresses and eliminated subgap photoresponse up to the photon energy of 2.9 eV. Even for NBLS with 2.7 eV photons, the threshold voltage shift is suppressed well to -4.4 V after 3 h of test. These results provide the following information: (i) passivation removes the surface deep subgap defects in a-IGZO and eliminates the subgap photoresponse, but (ii) the bulk defects in a-IGZO should be removed prior to the passivation process. The Y2O3-passivated TFT is not only stable for these stress conditions, but is also compatible with high-frequency operation with the current gain cut-off frequency of 91 kHz, which is consistent with the static characteristics. (C) 2011 Elsevier B.V. All rights reserved.