Correlating Growth Characteristics in Atomic Layer Deposition with Precursor Molecular Structure: The Case of Zinc Tin Oxide
Correlating Growth Characteristics in Atomic Layer Deposition with Precursor Molecular Structure: The Case of Zinc Tin Oxide
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DOI：
10.1021/cm403913r
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发表时间：
2014-05-13
影响因子：
8.6
通讯作者：
Bent, Stacey F.
中科院分区：
文献类型：
--
作者：
Tanskanen, Jukka T.;Hagglund, Carl;Bent, Stacey F.
采用DFT计算和原位四极杆质谱（QMS）研究了混合氧化物薄膜在原子层沉积（ALD）中的生长特性，以二乙基锌（DEZn）、四甲基（二甲氨基）锡（TDMASn）和水为原料制备了氧化锌锡（ZTO） ALD。dft计算的TDMASn在oh端氧化锌表面结合反应的吉布斯自由能表明该反应是可行的，并为在氧化锌ALD过程中加入少量SnOx循环降低表面反应位点密度提供了证据。原位QMS实验验证了SnOx循环过程中表面反应位密度的降低，并证明了在随后的ZnO循环过程中反应位密度的恢复。反应位点密度的降低是TDMASn前体的四种可交换配体的结果，为实验观察到的ZTO ALD生长特性提供了原子水平的解释。本文建立的ZTO ALD前体分子结构与材料生长之间的相关性适用于其他ALD过程，其中前体遵循配体交换表面化学，因此，它为理解和发展ALD过程提供了有用的一般指导原则。
The growth characteristics in atomic layer deposition (ALD) of mixed oxide thin films have been investigated by DFT calculations and in situ quadrupole mass spectrometry (QMS) using zinc tin oxide (ZTO) ALD from diethylzinc (DEZn), tetrakis(dimethylamido)tin (TDMASn), and H2O as a case study. The DFT-calculated Gibbs free energies of reaction for binding TDMASn on OH-terminated ZnO surfaces demonstrate the reaction to be feasible and provide evidence for a reduction in surface reaction site density upon mixing a small number of SnOx cycles into the ZnO ALD process. The in situ QMS experiments verify the reduction in surface reaction site density during the SnOx cycle, and demonstrate restoration of reaction site density during the subsequent ZnO cycles. The reduction in reaction site density, which is a consequence of the four exchangeable ligands of the TDMASn precursor, is shown to provide an atomic-level explanation for experimentally observed ZTO ALD growth characteristics. The correlation between precursor molecular structure and material growth established here for ZTO ALD applies to other ALD processes where precursors follow ligand-exchange surface chemistries, and thus, it provides general guiding principles useful in understanding and developing ALD processes.