Nitric acid method for fabrication of gate oxides in TFT
Nitric acid method for fabrication of gate oxides in TFT
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DOI：
10.1016/j.apsusc.2007.10.103
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发表时间：
2008-04
影响因子：
6.7
通讯作者：
S. Mizushima;S. Imai;Asuha;Masato Tanaka;H. Kobayashi
中科院分区：
文献类型：
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作者：
S. Mizushima;S. Imai;Asuha;Masato Tanaka;H. Kobayashi
我们开发了用硝酸（HNO3）制备薄膜晶体管（TFT）栅氧化层的sio2层低温形成方法。通过两步硝酸氧化法，分别使用40%和68wt%（共沸混合物）的hno3水溶液进行初始和后续氧化，可以在32cm×40cm基底上形成厚度均匀性良好（即±4%）的厚（bbb10 nm） sio2层。硝酸氧化使多晶硅薄膜表面的脊状结构高度大大降低。当32cm×40cm玻璃基板上的多晶硅薄膜在共沸点（即68wt% hno3水溶液在121℃下）氧化时，在多晶硅表面形成厚度均匀性良好（±0.05nm）的超薄（即1.1nm） sio2层。等离子体增强化学气相沉积法制备的SiO2/Si结构在68wt% HNO3中浸泡后，氧化物固定电荷密度大大降低，界面态消除。在200℃的温度下进行热处理，进一步降低了固定电荷密度，从而获得了与热SiO2/Si结构相同的电容-电压特性。
We have developed low temperature formation methods of SiO2layers which are applicable to gate oxide layers in thin film transistors (TFT) by use of nitric acid (HNO3). Thick (>10nm) SiO2layers with good thickness uniformity (i.e., ±4%) can be formed on 32cm×40cm substrates by the two-step nitric acid oxidation method in which initial and subsequent oxidation is performed using 40 and 68wt% (azeotropic mixture) HNO3aqueous solutions, respectively. The nitric acid oxidation of polycrystalline Si (poly-Si) thin films greatly decreases the height of ridge structure present on the poly-Si surfaces. When poly-Si thin films on 32cm×40cm glass substrates are oxidized at azeotropic point (i.e., 68wt% HNO3aqueous solutions at 121°C), ultrathin (i.e., 1.1nm) SiO2layers with a good thickness uniformity (±0.05nm) are formed on the poly-Si surfaces. When SiO2/Si structure fabricated using plasma-enhanced chemical vapor deposition is immersed in 68wt% HNO3, oxide fixed charge density is greatly decreased, and interface states are eliminated. The fixed charge density is further decreased by heat treatments at 200°C, and consequently, capacitance–voltage characteristics which are as good as those of thermal SiO2/Si structure are achieved.