Development of Methods for the design of Microfocus Optical Systems

本文建立了由扩展光源、两个椭球光栅和像面组成的面对称双元件光学系统的三级像差理论。导出了类似赛德尔像差的光斑图和像差曲线的解析公式。该理论被证明是通过一个递推公式推广到多元素系统。在此基础上，导出了Schwarzschild光学系统的解析像差曲线与光轴对准误差和凹、凸球面镜曲率中心间距的关系。在放大率为50倍、数值孔径为0.25、物像距为0.1m的条件下，利用光线追迹法进一步研究了各种因素对史瓦西物镜性能的影响。结果表明，采用0.69mm的非同心排列，在光轴上可获得30 nm的空间分辨率。建立了一种变线距平面光栅单色器的设计方法，其波长扫描是通过光栅绕面法线简单旋转实现的。结果表明，所设计的单色器在1-2 keV的能量范围内具有较高的通量。此外，标量理论被发展来估计最佳的脊槽比和层状光栅的槽深。设计、制造并测试了一种用于极紫外光刻（EUVL）的三非球面镜光学系统。通过用Fizeau型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。然后在同步辐射光束线上测试EUVL系统，并显示出56 nm的衍射极限性能。

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.