Multiphoton-Excited Deep-Ultraviolet Photolithography for 3D Nanofabrication
Multiphoton-Excited Deep-Ultraviolet Photolithography for 3D Nanofabrication
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DOI：
10.1021/acsanm.0c02519
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发表时间：
2020-11-25
影响因子：
5.9
通讯作者：
Fujita, Katsumasa
中科院分区：
文献类型：
--
作者：
Taguchi, Atsushi;Nakayama, Atsushi;Fujita, Katsumasa
在深紫外（DUV）波段，光与物质的相互作用在许多材料中表现出发光、光致异构和聚合等多种光学效应。尽管由于短波长而具有丰富的光化学和高空间分辨率，但由于缺乏与DUV兼容的光学元件和设备，因此无法将DUV光作为常规实验室工具用于显微镜和光刻。在这里，我们提出了使用双光子激发与可见激光实现光聚合的分子与激发能量相当于深紫外光。使用可见光的标准光学器件，我们用400 nm飞秒脉冲聚合甲基丙烯酸酯低聚物，而不添加任何光引发剂和敏化剂。通过在3D中扫描激光焦点，我们创建了一系列精细的3D结构，其最小分辨线空间特征为80 nm。我们发现，在DUV下由双光子吸收诱导的光聚合是令人惊讶的有效的，并且仅需要100 kW/cm（2）量级的激光强度。单体中天然存在的DUV吸收位点的使用简化了聚合反应，而不会通过添加引发剂而牺牲材料纯度，并促进了对不同材料的应用。我们已经将双光子DUV聚合应用于金属氧簇和氨基酸半胱氨酸。随着各种成功的演示，包括有机和无机材料制成的结构，多光子DUV聚合提供了一个独特的工具，在3D纳米器件的制造。
Light-matter interactions in the deep-ultraviolet (DUV) wavelength region exhibit a variety of optical effects such as luminescence, photoisomerization, and polymerization in many materials. Despite the rich photochemistry and high spatial resolution due to the short wavelength, the notorious lack of DUV-compatible optical components and devices precludes the use of DUV light in microscopy and lithography as a routine laboratory tool. Here, we present the use of two-photon excitation with visible laser light to realize photopolymerization of molecules with an excitation energy equivalent to DUV light. Using standard optics for visible light, we polymerized methacrylate oligomers with 400 nm femtosecond pulses without any addition of photoinitiators and sensitizers. By scanning the laser focus in 3D, we created a series of fine 3D structures with the smallest resolved line-space features of 80 nm. We found that photopolymerizations induced by two-photon absorption at DUV is surprisingly efficient and requires laser intensity only on the order of 100 kW/cm(2). The use of DUV absorption sites natively existing in monomers simplifies polymerization reactions without sacrificing material purities by adding initiators and facilitates applications to diverse materials. We have applied two-photon DUV polymerizations to metal-oxo clusters and the amino acid cysteine. With the variety of successful demonstrations including organic- and inorganic-material-made-structures presented, multiphoton DUV polymerization offers a distinct tool for fabrications of nanodevices in 3D.