Abstract

A two-mirror projection Schwarzschild objective (reduction ratio ×5), formed by two aspheric mirrors and developed as part of upgrading a lithographic workbench with the operating wavelength of 13.4 nm, is proposed. The measurement procedure and results of correction of the shape of the aspheric mirrors and aberrations of the objective lens in the assembled version are described in detail. As a result of several corrections of local errors by an ion beam, a root-mean-square deviation of the shape of the primary mirror of 0.8 nm is achieved. The objective-lens aberrations were equal to 5.4 nm. Simulation of the resolving power of the objective lens, taking into account the measured aberrations, shows that 200-nm-wide strips are resolved with a contrast of 32%, 100 nm—23%, and 30 nm—15%. The reflectivities of the multilayer Mo/Si mirrors with an anti-stress Cr/Y sublayer were 63–65% depending on the coordinate on the mirror. The reasons why it was not able to correct the aberration of the objective lens to the level of 1 nm necessary for achievement of the diffraction limit of resolution are discussed.

中文翻译：

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EUV平版印刷工作台的投影目标

摘要

提出了由两个非球面镜形成的，作为升级工作波长为13.4 nm的光刻工作台的一部分而开发的两镜投影Schwarzschild物镜（缩小率×5）。详细介绍了组装过程中非球面镜形状和物镜像差的测量程序以及校正结果。通过离子束对局部误差进行多次校正的结果是，实现了主镜形状的均方根偏差为0.8 nm。物镜像差等于5.4nm。对物镜分辨力的模拟（考虑到所测量的像差）显示，分辨出200 nm宽的条带的对比度为32％，100 nm–23％和30 nm–15％。带有抗应力Cr / Y子层的多层Mo / Si反射镜的反射率为63–65％，具体取决于反射镜上的坐标。讨论了为什么不能将物镜的像差校正到实现分辨率的衍射极限所必需的1 nm的水平的原因。