Role of Surface Termination in Atomic Layer Deposition of Silicon Nitride

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• 作者：Chaitanya Krishna Ande ; Harm C. M. Knoops ; Koen de Peuter ; Maarten van Drunen ; Simon D. Elliott ; Wilhelmus M. M. Kessels
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：September 17, 2015
• 年：2015
• 卷：6
• 期：18
• 页码：3610-3614
• 全文大小：262K
• ISSN：1948-7185

文摘

There is an urgent need to deposit uniform, high-quality, conformal SiN_x thin films at a low-temperature. Conforming to these constraints, we recently developed a plasma enhanced atomic layer deposition (ALD) process with bis(tertiary-butyl-amino)silane (BTBAS) as the silicon precursor. However, deposition of high quality SiN_x thin films at reasonable growth rates occurs only when N₂ plasma is used as the coreactant; strongly reduced growth rates are observed when other coreactants like NH₃ plasma, or N₂鈥揌₂ plasma are used. Experiments reported in this Letter reveal that NH_x- or H- containing plasmas suppress film deposition by terminating reactive surface sites with H and NH_x groups and inhibiting precursor adsorption. To understand the role of these surface groups on precursor adsorption, we carried out first-principles calculations of precursor adsorption on the 尾-Si₃N₄(0001) surface with different surface terminations. They show that adsorption of the precursor is strong on surfaces with undercoordinated surface sites. In contrast, on surfaces with H, NH₂ groups, or both, steric hindrance leads to weak precursor adsorption. Experimental and first-principles results together show that using an N₂ plasma to generate reactive undercoordinated surface sites allows strong adsorption of the silicon precursor and, hence, is key to successful deposition of silicon nitride by ALD.