High-resolution soft lithography: Enabling materials for nanotechnologies
High-resolution soft lithography: Enabling materials for nanotechnologies
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DOI：
10.1002/anie.200461122
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发表时间：
2004-01-01
影响因子：
16.6
通讯作者：
DeSimone, JM
中科院分区：
文献类型：
--
作者：
Rolland, JP;Hagberg, EC;DeSimone, JM
第5797章化学。国际。埃德。 2004, 43, 5796–5799 www. Angewandte。 org 2004 Wiley-VCH Verlag GmbH & Co. KGaA，Weinheim 使用三氯（1H、1H、2H、2H-全氟辛基）硅烷将其涂覆到图案化的硅晶片上，以允许脱模。当特征尺寸如此大时，基于 PFPE 的弹性体（图 2B）和基于 PDMS 的弹性体（图 2E）可以生成具有良好特征保真度的高质量复制模具。两个弹性体模具生成后，它们各自独立地与未固化 TMPTA 的小滴（直径 2 毫米）接触，该小滴首先放置在平坦的、未图案化的硅片上，如图 1B 所示。使用改良的 Instron 对模具施加固定压力，以确保保形接触。然后，使 UV 光穿过每个模具的背面 1 分钟，以在与模具接触的同时完全固化 TMPTA。然后将每个模具从晶圆上剥离，露出图案化的 TMPTA 复制品。由 PDMS 模具生成的 TMPTA 复制品质量非常差。这些复制品的 SEM 图像（图 2F 和 G）显示了 PDMS 模具的碎片，这些碎片是由于固化前 TMPTA 使 PDMS 模具膨胀而在脱模过程中被撕掉的。相比之下，那些由基于 PFPE 的模具制成的复制品看起来与母版相同，没有撕裂（图 2C 和 G），因为它不会被有机可溶性 TMPTA 光聚合物树脂溶胀。此外，基于 PFPE 的模具非常容易从微模制的 TMPTA 上剥离，这可能是因为基于 PFPE 的模具极低的表面能 [24] 及其弹性体性质。这种基于含氟聚合物的模具材料的固有疏油性质首次实现了使用软弹性体模具材料对常见有机物进行压印光刻应用。除了上面说明的基于 PDMS 的材料的固有膨胀问题之外，之前使用基于 PDMS 的弹性体（例如 Sylgard184）进行 1:1 亚 1 微米图案化的尝试并没有提供高保真度的复制品。事实上，即使使用复杂的预处理方法来减少模制物体与基于 PDMS 的复制品之间的界面粘附力，使用尺寸小于 1 微米的模具和基于 PDMS 的弹性体精确复制图案也只取得了有限的成功 [1,4,10]。为了测试基于 PFPE 的弹性体进行精确纳米级成型的可行性，我们选择使用图案化硅晶圆母模来制造复制模具，其特征宽度为 140 nm，深度约为 50 nm，间距为 70 nm（图 3A）。我们发现，我们可以使用基于 PFPE 的氟弹性体材料铸造出色的模具，同时精确保留图案化硅晶圆母版的纳米级特征（图 3B）。基于 PFPE 的模具上的特征的平均高度为 51 nm，这与硅母模中特征的测量高度 54 nm 非常吻合。基于 PFPE 的模具上特征的宽度似乎与顶部不同
5797 Angew. Chem. Int. Ed. 2004, 43, 5796–5799 www. angewandte. org 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim to the patterned silicon wafer using trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane was applied to allow release of the mold. Replica molds of high quality with good feature fidelity were generated from both the PFPE-based elastomer (Figure 2B) as well as the PDMS-based elastomer (Figure 2E) when the feature sizes were this large. Once both of the elastomeric molds were generated, they were each independently brought into contact with a small drop (% 2 mm in diameter) of the uncured TMPTA which was first placed on a flat, unpatterned silicon wafer as illustrated in Figure 1B. A fixed pressure was exerted on the mold with a modified Instron to ensure conformal contact. UV light was then passed through the back of each mold for 1 min to fully cure the TMPTA while in contact with the mold. Each mold was then peeled from the wafer revealing the patterned TMPTA replicate. The TMPTA replicates generated from the PDMS molds were of very poor quality. SEM images (Figure2F and G) of these replicates reveal pieces of the PDMS mold that were ripped out during the release as a result of swelling of the PDMS mold by the TMPTA prior to curing. In contrast, those replicates made from the PFPE-based mold look identical to the master with no tear out (Figure 2C and G) because it is not swollen by the organic-soluble TMPTA photopolymer resin. Additionally, the PFPE-based mold was extremely easy to peel away from the micromolded TMPTA, presumably because of the extremely low surface energy of the PFPE-based mold [24] and its elastomeric nature. The intrinsically oleophobic nature of this fluoropolymer-based mold material enables for the first time imprint lithographic applications of commonplace organics using soft elastomeric mold materials.In addition to the intrinsic swelling problems illustrated above for PDMS-based materials, previous attempts to perform 1: 1 sub 1-micron patterning using PDMS-based elastomers, such as Sylgard184, does not give replicas of high fidelity. Indeed, accurate replication of patterns using molds of features less than 1-micron in size with PDMS-based elastomers has had only limited success [1, 4, 10] even when using elaborate pre-treatment methods to reduce the interfacial adhesion between the object being molded and the PDMS-based replica. To test the viability of PFPE-based elastomers to perform accurate nanometer-scale molding we chose to fabricate replica molds from a patterned siliconwafer master with features having a width of 140 nm, a depth of approximately 50 nm, and a separation of 70nm (Figure3A). We found we could cast excellent molds using the PFPE-based fluoroelastomer materials with exact preservation of the nanoscale features of the patterned silicon-wafer master (Figure 3B). The features on the PFPE-based mold had an average height of 51 nm which was in excellent agreement with a measured height of 54 nm for the features in the silicon master. The widths of the features on the PFPE-based molds seem to vary from the top of the