Comparison of the Atomic Layer Deposition of Tantalum Oxide Thin Films Using Ta(NtBu)(NEt2)3, Ta(NtBu)(NEt2)2Cp, and H2O

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• 作者：Seul Ji Song ; Taehyung Park ; Kyung Jean Yoon ; Jung Ho Yoon ; Dae Eun Kwon ; Wontae Noh ; Clement Lansalot-Matras ; Satoko Gatineau ; Han-Koo Lee ; Sanjeev GautamDeok-Yong Cho ; Sang Woon LeeCheol Seong Hwang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：January 11, 2017
• 年：2017
• 卷：9
• 期：1
• 页码：537-547
• 全文大小：610K
• ISSN：1944-8252

文摘

The growth characteristics of Ta<sub>2sub>O<sub>5sub> thin films by atomic layer deposition (ALD) were examined using Ta(N<sup>tsup>Bu)(NEt<sub>2sub>)<sub>3sub> (TBTDET) and Ta(N<sup>tsup>Bu)(NEt<sub>2sub>)<sub>2sub>Cp (TBDETCp) as Ta-precursors, where <sup>tsup>Bu, Et, and Cp represent tert-butyl, ethyl, and cyclopentadienyl groups, respectively, along with water vapor as oxygen source. The grown Ta<sub>2sub>O<sub>5sub> films were amorphous with very smooth surface morphology for both the Ta-precursors. The saturated ALD growth rates of Ta<sub>2sub>O<sub>5sub> films were 0.77 Å cycle<sup>–1sup> at 250 °C and 0.67 Å cycle<sup>–1sup> at 300 °C using TBTDET and TBDETCp precursors, respectively. The thermal decomposition of the amido ligand (NEt<sub>2sub>) limited the ALD process temperature below 275 °C for TBTDET precursor. However, the ALD temperature window could be extended up to 325 °C due to a strong Ta–Cp bond for the TBDETCp precursor. Because of the improved thermal stability of TBDETCp precursor, excellent nonuniformity of ∼2% in 200 mm wafer could be achieved with a step coverage of ∼90% in a deep hole structure (aspect ratio 5:1) which is promising for 3-dimensional architecture to form high density memories. Nonetheless, a rather high concentration (∼7 at. %) of carbon impurities was incorporated into the Ta<sub>2sub>O<sub>5sub> film using TBDETCp, which was possibly due to readsorption of dissociated ligands as small organic molecules in the growth of Ta<sub>2sub>O<sub>5sub> film by ALD. Despite the presence of high carbon concentration which might be an origin of large leakage current under electric fields, the Ta<sub>2sub>O<sub>5sub> film using TBDETCp showed a promising resistive switching performance with an endurance cycle as high as ∼17 500 for resistance switching random access memory application. The optical refractive index of the deposited Ta<sub>2sub>O<sub>5sub> films was 2.1–2.2 at 632.8 nm using both the Ta-precursors, and indirect optical band gap was estimated to be ∼4.1 eV for both the cases.