Block copolymer (BCP) directed self-assembly (DSA) has been presented as a potential economically attractive enhancement to extend the capabilities of optical lithography for semiconductor manufacturing. One concern in DSA is the level of defectivity that can be achieved in such a process. Although entropic effects will always lead to some degree of defectivity, highly ordered structures with a low theoretical equilibrium defect density can be produced by guiding the ordering and placement of the BCP domains using a patterned underlayer. Recent experimental studies have shown that while DSA processes can significantly reduce the observed defect density, defectivity levels are generally still higher than allowable for high-volume manufacturing and higher than what would be anticipated from free energy estimates of the observed defect modes. In particular, bridge defects are one of the most commonly observed defect modes in experimental DSA studies. A number of hypotheses have been proposed to explain the origins of these defects. One hypothesis is that so-called affinity defects present in the underlayer can spawn bridge defects in the overlying BCP film. The goal of the work reported here was to investigate the extent to which bridge defects can be generated or further reinforced in lamellae-forming block copolymer films due to affinity defects in the underlayer pattern. Coarse-grained molecular dynamics simulations were used to simulate the chemoepitaxial DSA of monodisperse block copolymer films atop underlayers with varying affinity defect sizes. Affinity defects were simulated by creating circular regions of a single polymer block type (which is the opposite block type of that used to pattern the underlayer guiding stripes) in the nominally neutral background region of the underlayer. These affinity defects were positioned in regions of the underlayer where they were the incorrect type to match the overlying block copolymer pattern. It was observed that the presence of an affinity defect in the neutral region of the underlayer caused the energetically preferential polymer block to wet the affinity defect, thus creating the nucleus of what could potentially become a bridge defect—even when the affinity defects were very small. As the radius of the underlayer affinity defect (RoD) increased, the amount of block copolymer of incorrect type (with respect to a perfectly assembled copolymer pattern) that assembled above the affinity defect increased; but, in general, the thickness of the wetting layer in contact with the affinity defect was only roughly one polymer chain thick. These data suggest that an affinity defect in the underlayer alone is unlikely to be noticeably enhanced by significant bridge defect formation in a monodisperse block copolymer film.

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由化学外延引导底层中的局部误差引起的嵌段共聚物定向自组装缺陷模式：分子模拟研究

嵌段共聚物 (BCP) 定向自组装 (DSA) 已被认为是一种具有潜在经济吸引力的增强技术，可扩展用于半导体制造的光刻技术。DSA 中的一个问题是在这种过程中可以达到的缺陷水平。尽管熵效应总是会导致一定程度的缺陷，但通过使用图案化底层引导 BCP 域的排序和放置，可以产生具有低理论平衡缺陷密度的高度有序结构。最近的实验研究表明，虽然 DSA 工艺可以显着降低观察到的缺陷密度，但缺陷水平通常仍高于大批量制造所允许的水平，并且高于观察到的缺陷模式的自由能估计所预期的水平。特别是，桥接缺陷是实验 DSA 研究中最常见的缺陷模式之一。已经提出了许多假设来解释这些缺陷的起源。一种假设是底层中存在的所谓亲和缺陷会在上覆 BCP 膜中产生桥接缺陷。此处报告的工作的目标是研究由于底层图案中的亲和缺陷而在形成薄片的嵌段共聚物膜中可以产生或进一步增强桥接缺陷的程度。粗粒分子动力学模拟用于模拟单分散嵌段共聚物薄膜在具有不同亲和缺陷尺寸的底层上的化学外延 DSA。通过在底层的标称中性背景区域中创建单个聚合物嵌段类型（与用于图案化底层引导条纹的嵌段类型相反的嵌段类型）的圆形区域来模拟亲和性缺陷。这些亲和缺陷位于底层区域，在那里它们与上层的嵌段共聚物图案不匹配。据观察，底层中性区域亲和缺陷的存在导致能量优先聚合物嵌段润湿亲和缺陷，从而产生可能成为桥接缺陷的核——即使亲和缺陷非常小. 随着底层亲和缺陷（RoD）半径的增加，在亲和缺陷上方组装的不正确类型的嵌段共聚物（相对于完美组装的共聚物模式）的数量增加；但是，一般来说，与亲和缺陷接触的润湿层的厚度只有大约一个聚合物链厚。这些数据表明，单分散嵌段共聚物膜中形成的显着桥接缺陷不太可能显着增强底层中的亲和缺陷。