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Development of Methods for the design of Microfocus Optical Systems

微焦点光学系统设计方法的发展

基本信息

批准号：
10650034
负责人：
NAMIOKA Takeshi
金额：
$ 2.18万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650034/
关键词：
Microfocus Double-element optical system Schwarzschild optics Telecentric optical system Ray tracing Aberration analysis Spot diagram EUVL シャバルツシルト光学系

项目摘要

A third-order aberration theory has been developed for a plane-symmetric double-element optical system that consists of an extended source, two ellipsoidal gratings, and an image plane. Analytic formulas were derived for spot diagrams and aberration curves similar to Seidel aberrations. The theory was shown to be extended to multi-element systems by means of a recurrence formula. Analytic aberration curves were also derived, on the basis of the theory, for Schwarzschild optics as a function of axis alignment error and the distance between the centers of curvature of the concave and convex spherical mirrors. The effects of various factors on the performance of a Schwarzschild objective was further investigated by means of ray tracing on condition that the objective had a magnification of 50, a numerical aperture of 0.25, and an object-to-image distance of 〜1 m. the result showed that a spatial resolution of 30 nm could be obtained on the optical axis by arranging the mirrors non-concentrically by an amount of 0.69 mm. A design method was established for a varied-line-spacing plane grating monochromator, whose wavelength scanning was made by simple grating rotation about the surface normal. The result showed that the designed monochromator was capable of providing a high throughput in an energy range of 1-2 keV. In addition, a scalar theory was developed to estimate the optimum land-to-groove ratio and groove depth of a laminar grating. A three-aspheric-mirror optics for extreme ultraviolet lithography (EUVL) was designed, constructed, and tested. The mirrors were aligned to a precision of 3 nm RMS by successively adjusting the mirrors by amounts computed from wavefront errors measured with a Fizeau-type interferometer. The EUVL system was then tested on a synchrotron radiation beamline and showed a diffraction-limited performance of 56 nm.

本文发展了一个平面对称双元件光学系统的三级像差理论，该光学系统由一个扩展光源、两个椭球光栅和一个像面组成。推导出了类似于赛德尔像差的光点图和像差曲线的解析公式。通过递推公式，将该理论推广到多元素体系。在此理论的基础上，导出了Schwarzschild光学系统的像差解析曲线，它是轴向误差和凹凸球面镜曲率中心之间距离的函数。用光线追迹法进一步研究了各种因素对Schwarzschild物镜性能的影响，在物镜放大倍数为50，数值孔径为0.25，物像距离约为1m的条件下，通过非同心布置反射镜0.69 mm，可获得30 nm的光轴空间分辨率。建立了一种变线距平面光栅单色器的设计方法，该单色器的波长扫描是通过简单的光栅绕表面法线旋转进行的。结果表明，所设计的单色仪能够在1-2keV的能量范围内提供高通量。此外，还发展了一种标量理论来估算层流光栅的最佳地槽比和槽深。设计、制造和测试了一种用于极紫外光刻的三非球面光学系统。通过根据菲佐干涉仪测量的波前误差计算的量连续调整反射镜，将反射镜对准到3 nm RMS的精度。EUVL系统随后在同步辐射光束线上进行了测试，显示出56 nm的衍射限制性能。