Jin Qijian, Liang Gaofeng, Chen Gang, Zhao Fen, Yan Shaokui, Zhang Kun, Yang Mengyu, Zhang Qi, Wen Zhongquan, Zhang Zhihai
Opt Lett. 2020 Jun 1;45(11):3159-3162. doi: 10.1364/OL.389369.
Plasmonic lithography can utilize evanescent waves to produce subdiffraction patterns. However, the high loss and shallow depth of patterns severely obstruct its application in practice. In this work, a large focal depth is achieved for deep subwavelength lithography. It is accomplished by employing radially polarized light to excite surface plasmons on a concentric annular grating and combining designed epsilon-near-zero metamaterial to select a high spatial frequency mode, which can shape an evanescent Bessel beam in a photoresist (PR). Moreover, the intensity distribution of the subdiffraction beam can be further enhanced and uniformized by adding reflective layers. It is shown that a needle-like beam with a focal depth of over 500 nm (1.23) is formed in the PR layer, and the full width at half maximum of the beam is widened from only 80 nm (0.2) to 94 nm (0.23). The analyses indicate that this design is applicable for direct writing lithography to produce super-resolution patterns with small feature size, high aspect ratio, and strong field intensity.
表面等离子体光刻可以利用倏逝波来产生亚衍射图案。然而，图案的高损耗和浅深度严重阻碍了其在实际中的应用。在这项工作中，实现了用于深亚波长光刻的大焦深。这是通过使用径向偏振光来激发同心环形光栅上的表面等离子体，并结合设计的近零介电常数超材料来选择高空间频率模式来完成的，该模式可以在光刻胶（PR）中形成倏逝贝塞尔光束。此外，通过添加反射层可以进一步增强和均匀化亚衍射光束的强度分布。结果表明，在PR层中形成了焦深超过500nm（1.23）的针状光束，并且光束的半高宽从仅80nm（0.2）加宽到94nm（0.23）。分析表明，该设计适用于直接写入光刻，以产生具有小特征尺寸、高纵横比和强场强的超分辨率图案。
