Center for Materials Analysis, Research Institute for Advanced Materials, Seoul National University, 599 Gwanangno, Gwanak-gu, Seoul 151-742, Korea.
Microsc Microanal. 2013 Aug;19 Suppl 5:109-13. doi: 10.1017/S1431927613012440.
The interfacial layer between the Al₂O₃ layer and the Si₃N₄ layer formed after postdeposition annealing (PDA) of TaN/Al₂O₃/Si₃N₄/SiO₂/Si (TANOS) stacks was investigated using transmission electron microscopy (TEM), scanning transmission electron microscopy, and electron energy loss spectroscopy (EELS). From the result of the TEM analysis, it was found that the 2-nm-thick interface layer between Al₂O₃ and Si₃N₄ layers was amorphous. The high-loss EELS analysis showed that the phases of the interfacial layer weakly bound together instead of the substoichiometric silicon oxide and amorphous Al₂O₃ near the bottom interface of the crystalline Al₂O₃. The low-loss EELS analysis showed that aluminum existed in metallic state at the interface. Therefore, we speculated that SiO(x)N(y) could be formed by oxidation of Si₃N₄ during PDA and that metallic aluminum could be formed by the decomposition of weakly bound amorphous Al₂O₃ during electron irradiation. These complicated reactions near the interface could induce oxygen deficiency in the Al₂O₃ layer and finally degrade the retention properties of TANOS stacks.
采用透射电子显微镜（TEM）、扫描透射电子显微镜和电子能量损失谱（EELS）研究了 TaN/Al₂O₃/Si₃N₄/SiO₂/Si（TANOS）叠层经后沉积退火（PDA）后形成的 Al₂O₃层与 Si₃N₄层之间的界面层。从 TEM 分析的结果可以看出，Al₂O₃和 Si₃N₄层之间 2nm 厚的界面层是无定形的。高损耗 EELS 分析表明，界面层的相弱结合在一起，而不是晶态 Al₂O₃底部界面附近的亚化学计量氧化硅和非晶态 Al₂O₃。低损耗 EELS 分析表明，界面处的铝呈金属态存在。因此，我们推测在 PDA 过程中 Si₃N₄的氧化可能形成了 SiO(x)N(y)，而在电子辐照过程中弱结合的非晶态 Al₂O₃的分解可能形成了金属铝。这些界面附近的复杂反应会导致 Al₂O₃层中的氧缺乏，最终降低 TANOS 叠层的保持性能。
