Understanding inherent substrate selectivity during atomic layer deposition: Effect of surface preparation, hydroxyl density, and metal oxide composition on nucleation mechanisms during tungsten ALD,The Journal of Chemical Physics

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Understanding inherent substrate selectivity during atomic layer deposition: Effect of surface preparation, hydroxyl density, and metal oxide composition on nucleation mechanisms during tungsten ALD
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-11-22 14:30:39 , DOI: 10.1063/1.4967811
Paul C. Lemaire ₁ , Mariah King ₁ , Gregory N. Parsons ₁

Affiliation

Area-selective thin film deposition is expected to be important for advanced sub-10 nanometer semiconductor devices, enabling feature patterning, alignment to underlying structures, and edge definition. Several atomic layer deposition (ALD) processes show inherent propensity for substrate-dependent nucleation. This includes tungsten ALD (W-ALD) which is more energetically favorable on Si than on SiO₂. However, the selectivity is often lost after several ALD cycles. We investigated the causes of tungsten nucleation on SiO₂ and other “non-growth” surfaces during the WF₆/SiH₄ W-ALD process to determine how to expand the “selectivity window.” We propose that hydroxyls, generated during the piranha clean, act as nucleation sites for non-selective deposition and show that by excluding the piranha clean or heating the samples, following the piranha clean, extends the tungsten selectivity window. We also assessed how the W-ALD precursors interact with different oxide substrates though individual WF₆ and SiH₄ pre-exposures prior to W-ALD deposition. We conclude that repeated SiH₄ pre-exposures reduce the tungsten nucleation delay, which is attributed to SiH₄ adsorption on hydroxyl sites. In addition, oxide surfaces were repeatedly exposed to WF₆, which appears to form metal fluoride species. We attribute the different tungsten nucleation delay on Al₂O₃ and TiO₂ to the formation of nonvolatile and volatile metal fluoride species, respectively. Through this study, we have increased the understanding of ALD nucleation and substrate selectivity, which are pivotal to improving the selectivity window for W-ALD and other ALD processes.

中文翻译：

了解原子层沉积过程中固有的衬底选择性：表面制备，羟基密度和金属氧化物成分对钨ALD过程中成核机理的影响

区域选择性薄膜沉积对于先进的低于10纳米的半导体器件至关重要，它可以实现特征图案，与下层结构的对准以及边缘清晰度。几种原子层沉积（ALD）工艺显示出依赖于基底的成核的内在倾向。其中包括钨ALD（W-ALD），在硅上比在SiO ₂上在能量上更有利。但是，在几个ALD循环后，选择性通常会丢失。我们研究了WF ₆ / SiH ₄期间钨在SiO ₂和其他“非生长”表面上形核的原因。W-ALD过程确定如何扩展“选择性窗口”。我们建议在食人鱼清洁过程中产生的羟基充当非选择性沉积的成核位点，并表明通过排除食人鱼清洁或在食人鱼清洁之后加热样品，可以扩展钨的选择性窗口。我们还评估了W-ALD前体如何通过W-ALD沉积之前的各个WF ₆和SiH ₄预暴露与不同的氧化物基底相互作用。我们得出的结论是，重复进行SiH ₄预暴露可减少钨的成核延迟，这归因于SiH ₄在羟基位点上的吸附。此外，氧化物表面反复暴露于WF ₆，似乎形成金属氟化物。我们将钨在Al ₂ O ₃和TiO ₂上的不同成核延迟分别归因于非挥发性和挥发性金属氟化物的形成。通过这项研究，我们增加了对ALD成核和底物选择性的理解，这对于改善W-ALD和其他ALD工艺的选择性窗口至关重要。

更新日期：2016-11-23

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