Spatial coherence synthesis imaging

研究了空间相干合成成像理论和纳米结构衍射光学元件的制作技术，提出了产生超分辨图形的掩模设计的傅里叶迭代算法。在光瞳平面和像平面之间采用傅里叶迭代算法。通过100次左右的迭代，超分辨率图像的对比度变得足够高，在任意图案生成和高对比度图像生成之间存在权衡。为了克服这一问题，超分辨方向图的线宽被限制在λ/4nA。这使得能够将超分辨率图案的空间频率分量限制在最高空间频率附近，从而使对比度变得更高。通过将图案方向限制为一个方向，图案对比度得到了更大的改善。二维线图案分为水平线和水平线。对于两条有向线路，优化是独立执行的。由不同方向的线条组成的两幅超分辨率图像进行二次曝光，生成任意的二维超分辨率图形，利用矢量衍射理论而不是传统的标量衍射理论可以计算纳米结构光学元件的光学特性。在矢量绕射计算中引入了严格的耦合波分析。利用该理论研究了纳米结构的光学特性，确定了光学元件的空间周期和纵横比。提出了一种新的纳米结构制作技术，该技术利用一维精细图案的多个空间位移来产生更精细的图案。与目前用于批量生产的传统压花技术相比，该技术提供了更高的吞吐量和更高的图案精度。

The theory of spatial coherence synthesis imaging and the fabrication technique of diffractive optical elements having nano-structure are studied.The Fourier iterative algorithm was developed for the design of mask patterns which generate super-resolution patterns. The Fourier iterative algorithm was applied between the pupil plane and the image plane. The contrast of the super-resolution pattern became sufficiently high with about 100 iterations.There is the tradeoff between the arbitrary pattern generation and the high contrast image generation. In order to overcome this problem, the line width of the super-resolution patterns is limited to λ/4 NA. This enables to limit the spatial frequency components of the super-resolution patterns around the highest spatial frequencies so that the contrast becomes higher.The pattern contrast was more improved by limiting the pattern orientations to one direction. The two-dimensional line patterns are divided into horizontal lines and horizontal lines. The optimization is performed independently for both directional lines. Two super-resolution images, which consist of lines having different directions, are double-exposed to generate arbitrary two-dimensional super-resolution patterns.The optical characteristics of optical elements having nano-structure can be calculated by use of the vector diffraction theories, not by the conventional scalar diffraction theories. We introduced rigorous coupled-wave analysis for the vector diffraction calculation. We examined the optical characteristics with this theory and determined the spatial period and the aspect ratio of the optical elements.A new nano-structure fabrication technique was proposed, which uses several spatial shifts of a one-dimensional fine pattern to produce a much finer pattern. This technique offers the higher throughput and the higher pattern accuracy than the conventional emboss technique which is now used for the mass production.