Graphoepitaxial Assembly of Symmetric Block Copolymers on Weakly Preferential Substrates
Graphoepitaxial Assembly of Symmetric Block Copolymers on Weakly Preferential Substrates
复制标题
DOI：
10.1002/adma.201001669
复制
发表时间：
2010-10-08
影响因子：
29.4
通讯作者：
Gopalan, Padma
中科院分区：
文献类型：
--
作者：
Han, Eungnak;Kang, Huiman;Gopalan, Padma
嵌段共聚物（bcp）的自组装已经成为一种简单而强大的“自下而上”的方法，用于制造致密和周期性的纳米结构，因为它们微相分离成纳米级结构域。[1-5]一般来说，薄膜中bcp的微相分离会导致随机取向晶粒的形成。薄膜中这种低程度的横向有序导致使用化学[6-10]或地形[11-16]图图化衬底来定向组装bcp。BCP的石墨外延使用一种地形图型衬底，其中BCP的空间限制诱导微畴从限制的硬壁成核和传播。在一项开创性的工作中，Segalman等人展示了使用地形图型衬底将球形BCP与远程横向顺序对齐在各向异性畴的情况下，如圆柱体或片状形成的BCP，控制沿垂直和横向方向的畴的方向对于生成所需的图案几何是必不可少的。例如，圆柱体成形BCP可用于根据相对于衬底的畴方向创建线或点阵列。同样垂直取向的层状畴也可以产生线阵列。由苯乙烯（St）和甲基丙烯酸甲酯（MMA）组成的端羟基无规共聚物P （S-r-MMA）被广泛用作诱导PS-b-PMMA垂直取向的非优先层。从早期的研究中，已知含有~ 0.60苯乙烯的P （S-r-MMA）共聚物是有效的非优先缓冲层。[17,18]最近，我们[19-21]和其他人已经证明共聚物的组成窗口（所谓的垂直窗口）导致BCP域的垂直取向，这对于片状和圆柱形BCP是不同的。垂直窗口也取决于覆盖BCP的薄膜厚度。
Self-assembly of block copolymers (BCPs) has emerged as a simple and robust “bottom-up” method for fabricating dense and periodic nanostructures as they microphase separate into nanoscale domains.[1–5] In general, microphase separation of BCPs in thin films on unpatterned surfaces leads to the formation of randomly oriented grains. This low degree of lateral ordering in thin films has led to the use of chemically [6–10] or topographically [11–16] patterned substrates for the directed assembly of BCPs.Graphoepitaxy of BCPs uses a topographically patterned substrate where spatial confinement of BCP induces nucleation and propagation of microdomains from the confining hard walls. In a seminal work, Segalman et al. demonstrated the use of a topographically patterned substrate to align sphere-forming BCP with long-range lateral order.[11] In the case of anisotropic domains such as cylinder-or lamella-forming BCP, controlling the orientation of domains along the vertical and lateral directions is essential for generation of desired pattern geometry. For example, cylinder-forming BCP can be used to create either line or dot arrays depending on the domain orientation with respect to the substrate. Similarly perpendicularly oriented lamellar domains can also generate line arrays. Hydroxyl-terminated random copolymer P (S-r-MMA), composed of styrene (St) and methyl methacrylate (MMA), is widely used as a nonpreferential layer for inducing perpendicular orientation of PS-b-PMMA. From earlier studies, it is known that a P (S-r-MMA), copolymer containing∼ 0.60 styrene is effective as a nonpreferential buffer layer.[17, 18] More recently, we [19–21] and others [22] have shown that there is a compositional window (so-called perpendicular window) of the copolymer that results in perpendicular orientation of the BCP domains, which is different for the lamella-and the cylinder-forming BCP. The perpendicular window also depends on the film thickness of the overlaying BCP.