深紫外双层金属光栅偏振器的设计与分析

193 nm波长浸没式步进扫描投影光刻机是实现45 nm及以下技术节点集成电路制造的核心装备.增大数值孔径是提高光刻分辨率的有效途径,而大数值孔径曝光系统的偏振性能严重影响光刻成像质量.光刻机曝光系统偏振参数的高精度检测是对其进行有效调控的前提.基于光栅的偏振检测技术能实现浸没式光刻机偏振检测装置的小型化,满足其快速、高精度在线检测的需求,该技术中的关键部件是结构紧凑且偏振性能良好的光栅.本文基于反常偏振效应和双层金属光栅对TE偏振光的透射增强原理,采用严格耦合波理论和有限时域差分方法,设计了一种双层金属光栅偏振器.计算了该偏振器的初始结构参数,并通过数值仿真得到了其偏振性能关于各光栅参数的变化关系.仿真结果表明,中间层高度是影响TE偏振光透射增强的主要因素;垂直入射时TE偏振光的透过率可达到56.8%,消光比高达65.6 dB.与现有同波段金属光栅偏振器相比,所设计的光栅偏振器在保证高透过率的同时,消光比提升了四个数量级.     

Virtual shearing interferometry by digital holography

A novel method of virtual shearing interferometry (VSI) is proposed. In this method, the shearogram is obtained by interference of a real object wave-front and a virtual object wave-front. The former is optically recorded and then digitally reconstructed; and the latter is introduced digitally by repositioning or reforming the former. The obvious advantages of VSI over conventional shearing interferometry (SI) are its versatility, accuracy, and simplicity. Only one real field is necessary to produce shearogram; there is no need of any real shearing device or even the phase unwrapping computation; and the digital shear can take any possible form according to different purposes. Both the optical experiments and computer simulations with lateral shearing, 180° rotational shearing and double lateral shearing for evaluation of lens aberrations in the general case including spherical aberration, coma, astigmatism, defocus, and tilts based on phase-shifting interferometry are given to verify the effectiveness of this method.     

Fabrication of 50 nm period gratings with multilevel interference lithography

We have developed a multilevel interference lithography process to fabricate 50 nm period gratings using light with a 351.1 nm wavelength. In this process multiple grating levels patterned by interference lithography are overlaid and spatial-phase aligned to a common reference grating using interferometry. Each grating level is patterned with offset phase shifts and etched into a single layer to achieve spatial-frequency multiplication. The effect of the multilayer periodic structure on interference lithography is examined to optimize the fabrication process. This process presents a general scheme for overlaying periodic structures and can be used to fabricate more complex periodic structures.     

Double-image encryption based on joint transform correlation and phase-shifting interferometry

An image encryption method combining the joint transform correlator (JTC) architecture with phaseshifting interferometry to realize double random-phase encoding is proposed. The encrypted field and the decrypting key are registered as holograms by phase-shifting interferometry. This method can encrypt two images simultaneously to improve the encryption efficiency of the methods based on JTC architecture, and eliminate the system alignment constraint of the methods based on Mach-Zehnder interferometer (MZI)architecture. Its feasibility and validity are verified by computer simulations. Moreover, image encryption and decryption can be achieved at high speed optically or digitally. The encrypted data are suitable for Internet transmission.     

Φ2 m平面反射镜低频轮廓非接触测量设备研制进展

口径2 m的高质量平面反射镜可用于大口径光电设备像质评价和性能检测,但受使用环境影响,平面反射镜的面形精度不易长期保持稳定,因此需要在使用前对其面形精度进行现场、快速校验,而常规的全口径或子孔径干涉检测均难以满足上述需求。由于反射镜面形在制造过程引入的中高频误差已处于稳定状态,环境扰动只引入低频像差,而选择子孔径斜率扫描再重构波面低频轮廓的方法较适于面形精度现场校验。提出双五棱镜配合双测角仪进行子孔径斜率同步差分测量的方法,可改善长测量周期内环境扰动引起的随机误差。并对测量设备光学、机械及控制系统进行设计,提出采用2台S-H传感器代替传统测角仪用于子孔径斜率测量的解决方法。验证试验结果表明,波面重构算法以及仪器测角精度可满足面形测量精度需求,其与ZYGO干涉仪测量结果的互差小于20 nm（RMS）。     

Review of Recent Zoom Lens Developments for 35 mm Cinematography at Panavision

A series of high performance zoom lens objectives developed by Panavision over fifteen years, which are very popular in the motion picture (cine) industry, are described. Various aspects of four cine zoom lenses, including; definitions, development, specification, construction, aberrations and tolerances, are discussed.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

The Double Monochromator Geometric Theory and Compensation of Aberrations

The light path function for the double monochromator is constructed, and the formulas of account of the members of its expanding in ascending power series adequate for the defocusing and the first order astigmatism aberrations are found. On the basis of results of the minimisation of obtained expressions the opportunity of construction of a double monochromator so that the second monochromator fractionally compensates aberrations of the first one is analysed. It is also noticed, that in the scheme of the double monochromator under certain conditions compensation of an astigmatism of the second order is automatically carried out. It allows to use a deviation angle of the scheme for more complete compensation of other aberrations and to develop double monochromators with the improved performances.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

A Novel Fabrication Technique of Long Period Fiber Gratings Using a Holographic Optical Element

We develop a new flexible and precise ultraviolet exposure technique to fabricate a long period fiber grating using a computer-generated holographic optical element (HOE). The HOE can generate a striped beam pattern with about a 300 #x03BC;m period from a KrF excimer laser. This method offers (1) ease in varying the grating period and (2) grating period precision. We achieve a grating period within an accuracy of #x00B1;0.04 #x03BC;m. This means that the peak wavelength can be controlled within an accuracy of #x00B1;0.2nm with an operating wavelength of 1.55 #x03BC;m.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Effects of third-order aberrations on the irradiance of self-image

We examine the effects of third-order aberrations exerted on the irradiance of image that is observable in a coherent self-imaging system. Both spherical aberration and astigmatism degrade the visibility of the image of a sinusoidal-type grating as well as blur the outline of the image of a rectangular-type grating. Coma laterally shifts the image of a sinusoidal-type grating on the image plane as well as changes a rectangular-type pattern into an asymmetrically blurred pattern. According to our analysis, the self-image of a high-density grating with a period of two times the optical wavelength is not at all affected by spherical aberration. In general a self-imaging system can always be corrected for astigmatism by shifting the image plane in its normal direction. We show that the self-image with defect can be well explained by taking the third-order aberrations and the focus-shift aberration into consideration.     

Analysis of Near-Field Intensity Distributions of High-Compression Talbot Array Illuminators Using Rigorous Diffraction Theory

The technology nowadays employed in the field of binary optics allows a relatively easy fabrication of grating structures down to the wavelength region. The analysis of light propagation through such grating structures requires the use of rigorous diffraction theories such as the rigorous coupled-wave analysis (RCWA), in order to take proper account of polarization effects in the electric and magnetic field and the thickness of the grating. In this paper, we examine the near-field intensity distributions and associated illumination efficiencies of Talbot array illuminators (TAIL#x0027;s) with compression ratios of 8 and 16 using RCWA. The high illumination efficiency observed close to the grating surface is expected to bring about new applications of TAIL#x0027;s in the field of super-resolution and near-field optics.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Subnanometer-accuracy z-position monitor mask for optical lithography

A lithographic test pattern, the phase shift grating (PSG) z monitor, is introduced. Through the use of phase shift techniques, position errors of images in the z-direction translate into lateral shifts in the printed pattern. The lateral shifts are easily measurable using an overlay metrology tool. Each z monitor pattern in a test mask can be directly read for the sign and magnitude of the z error. When the experimental conditions, namely, the period of a PSG and a coherent factor of the lithography tool simultaneously satisfies a criterion of the asymmetric two-beam interference between the zeroth-order ray and either of the two first-order rays of diffraction, the linearity of a z-vs-overlay curve is always complete and the slope of the curve is constant everywhere in the image field. Using state-of-the-art overlay metrology tools, we realized subnanometer-order accuracy in the z measurement.     

红绿共振互补光变亚波长微结构制作与分析

剖析了双层亚波长光栅微结构的设计及制作原理,提出了一种亚波长微结构设计与制作的新方法,其特点是以矩形亚波长光栅设计微结构,用全息干涉光刻及涂布的方法制作,却不影响设计微结构的共振及光变特性,还能改善反射光的颜色质量。用该方法设计及制作了具有“红绿”共振互补光变效果的亚波长防伪微结构,检验了其共振光变光谱与颜色变化特征。研究表明：制作的全息光栅微结构的共振及光变特征如共振光谱、颜色、光谱峰及峰分裂等与预先设计的相同;矩形亚波长光栅并不是共振的必要条件,其他面形光栅微结构的衍射特性和等效波导若与矩形光栅微结构的相同,则其相关特性相同;用新方法设计及制作亚波长光变微结构的工艺是可行的,既降低了设计微结构的加工难度,又便于用现有的全息生产设备批量生产。     

Digital moiré fringe measurement method for alignment in imprint lithography

Accurate layer-to-layer alignment, which is of prime importance for the fabrication of multilayer nanostructures in integrated circuits, is one of the main obstacles for imprint lithography. Current alignment measurement techniques commonly involve an image detection process for coarse alignment followed by a grating interference process for fine alignment. Though this kind of two-level alignment system is reasonable for measurement, when it is used in real imprint lithography, it is inconvenient because of the existence of a complex loading system that needs space for alignment. In this study, we propose a fine alignment method using only image detection using grating images and digital moiré fringe technology. In this method, though the gratings are also selected as alignment marks for accurate measurement, they do not interfere with the physics. The grating images captured from the template and wafer are used to measure angular displacement and to form parallel digital moiré fringes. The relative linear displacement between the template and wafer is determined by detecting the spatial phase of parallel digital moiré fringes. Owing to the magnification effect of digital moiré fringes, this method is capable of generating accurate measurements. According to the experimental results, this digital moiré fringe technique is accurate to less than 10 nm. In addition, without a complex grating interference system, this method has the advantage of being easy to operate.     

Design of the Optimum Holographic Optical Element Lens Using the Hologram Computer-Aided Design Tool

A hologram CAD (computer-aided design) tool capable of designing holographic optical element (HOE) is described. We have been developing this tool which is specialized for holograms. An optimum HOE lens with high diffraction efficiency and diffraction limited imaging characteristics is designed with the tool by applying a computer generated hologram (CGH) which generates an aspherical wave. The imaging characteristics of the HOE lens are experimentally verified and desirable results are obtained.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Measurement of Wavefront Aberration of Human Eye Using Talbot Image of Two-Dimensional Grating

The measurement of human ocular aberration is now frequently performed because of the increase in refractive surgery on the human cornea. The Hartmann-Shack (H-S) wavefront sensor is considered to be the most useful wavefront sensor, and a calculation method for wavefront aberration has been established. New methods of measuring wavefront aberrations of human eyes, using the Talbot image of a two-dimensional grating as a wavefront sensor and local shift of the Talbot image to calculate tilt of the wavefront are shown. The shift of the Talbot image was determined by comparing the phases of fundamental spatial frequency between the grating and the local patch of the Talbot image by Fourier transformation. The actual experiment was performed using a modified commercially available wavefront analyzer. Using these methods, Talbot images were obtained from model eyes and a human eye, and wavefront shapes were successfully reconstructed. Wavefront aberrations can be measured even when the obtained image is degraded by defocusing or scattering.     

Planar self-aligned imprint lithography for coplanar plasmonic nanostructures fabrication

Nanoimprint lithography (NIL) is a cost-efficient nanopatterning technology because of its promising advantages of high throughput and high resolution. However, accurate multilevel overlay capability of NIL required for integrated circuit manufacturing remains a challenge due to the high cost of achieving mechanical alignment precision. Although self-aligned imprint lithography was developed to avoid the need of alignment for the vertical layered structures, it has limited usage in the manufacture of the coplanar structures, such as integrated plasmonic devices. In this paper, we develop a new process of planar self-alignment imprint lithography (P-SAIL) to fabricate the metallic and dielectric structures on the same plane. P-SAIL transfers the multilevel imprint processes to a single-imprint process which offers higher efficiency and less cost than existing manufacturing methods. Such concept is demonstrated in an example of fabricating planar plasmonic structures consisting of different materials.     

嵌入式三色光变器设计

为解决目前亚波长二元矩形结构在光学防伪应用方面存在的防伪性能有待提升、制作困难导致性能劣化等问题,提出正弦结构等效矩形结构实现基于嵌入式亚波长一维单周期正弦结构的三色光变器.模拟仿真表明,亚波长正弦结构与原亚波长矩形结构性能相似,可获得优越的三色变换功能.当自然光以45°角入射时,可在方位角0°,58°,90°分别获得相应的蓝光、绿光、红光三色反射峰,反射率分别达到90%,89%,100%.分析并提出了该器件周期、槽深、膜厚以及入射角变化对反射峰的影响规律,探索了运用无掩模的双光束干涉曝光法制作母版的实验过程.提出的正弦结构三色光变器实现了方位角调节的高衍射效率自然光三色光变效果,突破了目前两色光变防伪的局限,同时降低了制作难度,可用通用的全息生产技术制作光栅结构,在光变图像防伪领域有重要应用.     

Interferometric testing of the spacing error of a plane diffraction grating

Two measuring methods of the plane diffraction grating spacing error are presented in this work. The first one resembles real- time holographic interferometry. The hologram is exposed when an object beam is the nth diffraction order, and is then illuminated by the -nth diffraction order wave. The second method makes use of double-exposure holographic interferometry. The first exposure is performed when the nth diffraction order is an object beam. During the second exposure the -nth diffraction order is an object beam. Both methods allow to measure the spacing error separately, not only from the grating surface error but also from the aberrations introduced by the other optical elements of the set-up.     

Quadric wavefront aberrations in phase-type images of binary amplitude gratings with small opening ratios

We discuss the quadric wavefront aberration of a fractional Talbot imaging ray which distorts the phase-type image of a binary amplitude grating with a small value of the opening ratio. When the opening ratio is equal to 1/2 or 1/3, the imaging rays are shown to have no quadric wavefront aberrations. For the opening ratios of 1/4 and 1/5, two different types of quadric wavefront aberrations are responsible for the three-level phase images. If the opening ratio gets to 1/6, we find that three different types of quadric wavefront aberrations distort the fractional Talbot image. The quadric wavefront aberration formulated here may be used in evaluating the phase-type image of a binary amplitude grating with an arbitrary value of the opening ratio.     

人眼高阶像差校正和视觉分析系统

人眼除具有可用眼镜或接触镜校正的低阶像差(离焦、像散)之外,还普遍存在高阶像差。高阶像差的存在影响着屈光系统的成像质量。为研究高阶像差对视觉功能的影响,利用自适应光学技术,建立了具有校正高阶像差和产生高阶像差双重功能的人眼高阶像差校正和视觉分析系统。介绍了系统实现高阶像差校正和视觉分析的工作原理;阐述了波前校正器、哈特曼波前探测系统、控制系统等关键单元技术;列出了系统对泽尼克模式像差的校正效果,绝大多数像差从0.5λ降低到0.2λ以下;阐明系统功能的实现过程,并给出仿真实验的结果。该系统为进一步研究高阶像差对视功能的影响提供了有效的手段。