Optical coatings for DUV Lithography
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摘要: 深紫外波段是目前常规光学技术的短波极限,随着波长的缩短,深紫外光学薄膜开发面临一系列特殊的问题;而对于深紫外光刻系统这样的典型超精密光学系统来说,对薄膜光学元件提出的要求则更加苛刻。本文主要介绍了适用于深紫外光刻系统的薄膜材料及膜系设计;对薄膜沉积工艺、元件面形保障、大口径曲面均匀性等超精密光学元件的指标保障关键问题进行了讨论;对环境污染与激光辐照特性等光刻系统中薄膜元件环境适应性的重要因素进行了深入分析。以上分析为突破高性能深紫外光刻光学薄膜开发瓶颈,更好地满足深紫外光刻等极高精度光学系统的应用需求指明了方向。Abstract: Deep-ultraviolet(DUV) is the shortest wavelength of conventional optical techniques. With the wavelength shrinks, DUV optical coatings are confronted with a series of technical problems. As a kind of typical ultra precision optical system, DUV lithography system proposes stringent requirements on DUV coating optics. In this paper, coating materials and the coating design procedures of DUV coatings are summarized. Then, key problems on the guarantee of optical properties are discussed such as coating deposition techniques, surface figure preservation of coated optics, coating thickness distribution correction of large curved surfaces. Finally, detailed analysis for the environmental adaptability of DUV coatings are made to critical factors such as the environmental contaminations and the laser irritation characters. The above analysis points out directions to breakthrough bottlenecks on the development of DUV lithograph coatings and meet the requirements of ultra-precision DUV optical systems.
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图 1 不同温度下制备AlF3薄膜的光学性能老化曲线
Figure 1. Aging effect of AlF3 coatings prepared at different substrate temperatures
图 2 由倾斜沉积导致的薄膜结构差异
Figure 2. Micro structure difference on coatings caused by oblique angle deposition
图 3 利用偏振光追迹分析减反膜引起的切趾
Figure 3. Apodization analysis of AR coatings by using polarization ray tracing
图 4 氟化物薄膜充氟后处理前后(a)薄膜微观结构与(b)透过率/反射率曲线对比
Figure 4. Changes of (a)microstructure and (b)transmission/reflectance spectra of fluoride coatings before and after postfluorination
图 5 离子束溅射制备减反膜透过率/反射率曲线
Figure 5. Transmission/reflectance curves of an AR coating prepared by ion beam sputter method
图 6 溶胶-凝胶法制备减反膜透过率曲线
Figure 6. Transmission curve of an AR coating prepared by solgel method
图 7 热蒸发制备减反膜透过率/反射率曲线
Figure 7. Transmission/reflectance curves of an AR coating prepared by thermal evaporation method
图 8 镀膜前后元件波前与应力双折射变化
Figure 8. Changes of (a)wavefront and (b)birefringence of a lens due to the coating process
图 9 典型12吋凸面元件膜厚均匀性校正结果
Figure 9. Typical results of thickness correction on a 12-inch convex surface
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