Chang Tzu-Hsuan, Xiong Shisheng, Liu Chi-Chun, Liu Dong, Nealey Paul F, Ma Zhenqiang
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Institute for Molecular Engineering, University of Chicago, IL, 60637, USA.
Macromol Rapid Commun. 2017 Sep;38(18). doi: 10.1002/marc.201700285. Epub 2017 Jul 27.
The direct self-assembly of cylinder-forming poly(styrene-block-methyl-methacrylate) (PS-b-PMMA) block copolymer is successfully assembled into two orientations, according to the underlying guiding pattern in different areas. Lying-down and perpendicular cylinders are formed, respectively, depending on the design of chemical pattern: sparse line/space pattern or hexagonal dot array. The first chemical pattern composed of prepatterned cross-linked polystyrene (XPS) line/space structure has a period (L ) equal to twice the intercylinder period of the block copolymer (L ). The PS-b-PMMA thin film on the prepared chemical template after thermal annealing forms a lying-down cylinder morphology when the width of the PS strips is less than the width of PS block in the PS-b-PMMA block copolymer. The morphology is only applicable at the discrete thickness of the PS-b-PMMA film. In addition to forming the lying-down cylinders directly on the XPS guiding pattern, the cylinder-forming block copolymer can also be assembled in a perpendicular way on the second guiding pattern (the hexagonal dot array). The block copolymer films are registered into two orientations in a single directed self-assembly process. The features of the assembled patterns are successfully transferred down to the silicon oxide substrate.
通过不同区域的底层引导图案，能够成功地将形成圆柱体的聚（苯乙烯 - 嵌段 - 甲基丙烯酸甲酯）（PS - b - PMMA）嵌段共聚物直接自组装成两种取向。根据化学图案的设计，即稀疏线/间距图案或六边形点阵，分别形成平躺和垂直的圆柱体。由预图案化的交联聚苯乙烯（XPS）线/间距结构组成的第一种化学图案的周期（L）等于嵌段共聚物的圆柱间距周期的两倍（L）。当PS条带的宽度小于PS - b - PMMA嵌段共聚物中PS嵌段的宽度时，在制备的化学模板上进行热退火后的PS - b - PMMA薄膜形成平躺圆柱体形态。该形态仅适用于PS - b - PMMA薄膜的特定厚度。除了直接在XPS引导图案上形成平躺圆柱体之外，形成圆柱体的嵌段共聚物还可以在第二种引导图案（六边形点阵）上以垂直方式进行组装。在单一的定向自组装过程中，嵌段共聚物薄膜被排列成两种取向。组装图案的特征成功地转移到了氧化硅衬底上。
