Hong Seongchul, Kim Jung Sik, Lee Jae Uk, Lee Seung Min, Kim Jung Hwan, Ahn Jinho
J Nanosci Nanotechnol. 2015 Nov;15(11):8652-5. doi: 10.1166/jnn.2015.11512.
In addition to the development of extreme ultraviolet lithography (EUVL), studies on beyond extreme ultraviolet lithography (BEUVL), which uses radiation with a wavelength of 6.7 nm, are in progress for their application in high-volume manufacturing. The BEUV wavelength, which is much shorter than the EUV wavelength, improves the resolution of patterned features. However, suitable materials for the mask stack of BEUVL are still under development. In this study, the applicability of metallic materials, such as Ni, Co, Ir, W, and Ta, as the absorber in a binary-intensity BEUVL mask was evaluated. The mask-imaging properties were simulated by adopting a thickness that ensured a reflectivity of <1% for each material. Furthermore, we used a multilayered La/B mirror--which exhibited a high reflectivity at a wavelength of 6.7 nm--because BEUV light is absorbed by most materials, and therefore uses reflective optics as desired. The numerical aperture (NA), angle of incidence, and demagnification factor were 0.5 and 0.6, 6 degrees, and 8x, respectively. We confirmed that a line-and-space pattern with a half-pitch of 11 nm can be patterned with metallic absorbers by using a high NA.
除了极紫外光刻（EUVL）技术的发展外，针对波长为6.7 nm的超极紫外光刻（BEUVL）的研究也在进行中，以将其应用于大规模制造。BEUV波长比EUV波长短得多，这提高了图案化特征的分辨率。然而，适用于BEUVL掩膜堆栈的材料仍在开发中。在本研究中，评估了诸如Ni、Co、Ir、W和Ta等金属材料作为二元强度BEUVL掩膜中吸收体的适用性。通过采用确保每种材料反射率<1%的厚度来模拟掩膜成像特性。此外，我们使用了多层La/B镜——其在6.7 nm波长处表现出高反射率——因为BEUV光会被大多数材料吸收，因此需要使用反射光学器件。数值孔径（NA）、入射角和缩小倍率分别为0.5和0.6、6度和8倍。我们证实，通过使用高NA，可以用金属吸收体对半间距为11 nm的线宽和间距图案进行光刻。
