三光束激光干涉光刻的实现方法

分析了多光束空间分布产生的误差对图形的影响,通过计算优化得到三光束产生的干涉图形在整个面内有着更好的图形稳定性。利用氦镉激光光源通过特定的光学系统形成空间分布近似旋转对称的三束光, 对光致抗蚀剂进行干涉曝光,制作出了周期600 nm、高度350 nm的蜂窝状点阵,测量结果表明该系统具有很好的图形重复性和稳定性,同时降低了对于光学光路的精密性要求。     

多光束激光干涉光刻图样

利用电磁理论,研究了多光束激光干涉图样的产生原理,结合计算机数值模拟和相关实验结果,分析了干涉图样的影响因素。研究结果表明：多光束激光干涉图样可以看成是多组余弦分布的平行线条纹的叠加;相干光束的偏振方向、入射方向、光束间相差是干涉图样的重要影响因素,改变这些因素,余弦分布的平行线条纹的振幅、置、周期和方向发生变化,图样也随之变化。     

Large-area surface-plasmon polariton interference lithography

Large-area surface-plasmon polariton (SPP) interference lithography is presented, which uses an attenuated total reflection-coupling mode to excite the interference of the SPPs. The interference of the SPPs causes a highly directional intensity range in a finite depth of the electric field, which is good for noncontact. Finite-difference time-domain simulations of the interference on a thin resist layer show that broad-beam illumination with a p-polarized light at a wavelength of 441 nm can produce features as small as 60 nm with high contrast, smaller than lambda/7. Our results illustrate the potential for patterning periodic structures over large areas at low cost.     

Design of a tilted two-mirror system

Formulae have been derived for eliminating main aberrations on the center of field of the tilted two-mirror system (TTS). The spherical aberration may be eliminated by considering the TTS as a co-axial system. The coma on the center of field will be reduced by conserving certain relationships between the tilting angles of the primary mirror and the secondary. In order to cancel the astigmatism on the center of field, one of the two mirrors must have bi-curvature at the vertex of the mirror. Ray tracing shows that the TTS solved by the given equations produces quite good image quality within a small field of view. In order to increase the useful field of view, the bi-curvature mirror with the shape 0L an inverse ellipsoid must have high order terms in its surface equation.     

Eliminating the undercut phenomenon in interference lithography for the fabrication of nano-imprint lithography stamp

We show an easy method to eliminate the undercut profile of photoresist by fabricating periodic nano-patterns on a substrate using interference lithography. An undercut phenomenon occurs frequently on the sidewall of photoresist patterns because of the 3-dimensional intensity distribution generated when two beams are merged to make an interferogram. This is mainly caused by the vertical interference between the incident beam and the one reflected from the surface of a substrate, and bottom-anti-reflection-coating (BARC) material is usually used to prevent beams from being reflected onto the substrate. We propose a simple post-process which helps researchers fabricate well-defined patterns without using BARC material. We developed this process to fabricate stamps for nano-imprint lithography at low cost, and show the results of our nano-imprint process which transfers patterns on a stamp directly through thermal resist.     

Fast sub-micrometer interference lithography on Silicon

Received: 4 February 1998/Revised version: 18 February 1998     

两镜反射系统自适应装调技术研究北大核心CSCD

为了满足两镜反射系统对光学元件高精度的装调、定位要求,以及系统工程化应用对可靠性与装调效率的要求,提出了一种基于人工神经网络(ANN)的自适应装调技术。基于矢量波像差理论分析两镜系统波像差与失调量的映射关系,在Keras框架下搭建ANN,并以非解析思路构建了自适应装调模型,开发了自适应装调装置,使失调次镜的平移调校精度优于2μm,倾斜调校精度优于2″,解决了算法设计与精度优化、反射镜组微应力固联等技术难题,并对某双抛无焦系统完成了自适应装调验证。试验结果表明:运用该装调技术,两镜反射系统装调后波像差优于λ/16、装调周期大幅缩短、装配可靠性通过环境试验考核,为该技术的工程化应用打下了基础。     

Vertical nanopatterning of 6H-SiC(0001) surfaces using gold-metal nanotube membrane lithography

Large-area membranes consisting of arrays of gold metal nanotubes were used as shadow masks to generate vertical nanopatterned 6H-SiC(0001) substrates. The gold membranes are formed by a replication technique based on electrochemical deposition of anodic aluminium oxide membranes or silicon substrates containing lithographically generated etch pits. Using the gold metal membranes as masks in reactive ion etching, spatially well-resolved protrusions in the SiC substrate were etched, arranged in periodic and non-periodic two-dimensional arrays. Final vertical morphological reorganizations were obtained in a hot-wall reactor under hydrogen flow. The obtained large-area networks of nano-objects have many potential applications in magnetism, electronics and biology. PACS 61.46.+w; 68.37.-d; 81.65.Cf     

一种新型的两镜三反射光学系统设计

 结合反射系统中双反射和三反射各自的优缺点,提出一种特殊的两镜三反光学系统,给出其初始结构的确定方法。对其结构优化过程中,在系统次镜后加平面反射镜,将系统进行折轴处理,然后在折轴反射镜后加透镜来校正剩余像差。该系统初始结构中两反射镜组成的是一个无焦系统,在主镜发生2次反射后成像。分析该初始系统的缺陷,对补偿该缺陷并使其成像质量达到衍射极限的后续补偿系统进行了设计。应用该方法设计了焦距f=5000mm,F数均为5,全视场角分别为0.4°和1°的2个系统,从像质评价结果可以看出,系统成像质量接近衍射极限,具有长焦距、小尺寸等特点。     

Non-approximate method for designing annular field of two-mirror concentric system

Annular field aberrations of a three-reflection concentric system,which are composed of two spherical mirrors,are analyzed.An annular field with a high level of aberration correction exists near the position where the principal ray is perpendicular to the object-image plane.Aberrations are determined by the object height and aperture angle.In this letter,the general expression of the system aberration is derived using the geometric method,and the non-approximate design method is proposed to calculate the radii of the annular fields that have minimum aberrations under different aperture angles.The closer to 0.5（the ratio of the radius of convex mirror to the radius of concave mirror）is,the smaller the system aberration is.The examples analyzed by LABVIEW indicate that the annular field designed by the proposed method has the smallest aberration in a given system.     

Scalable interference lithography alignment for fabrication of three-dimensional photonic crystals

Holographic lithography is an ideal technique for fabricating three-dimensional photonic crystals. However, a critical stage in the fabrication is the minute alignment of the layers with one another. We present a simple moirelike alignment technique with better than 20-nm translation resolution and 45-murad rotation resolution. This technique can easily be extended to other situations when low-cost, high-precision alignment is needed.     

Concept for testing two-mirror optical telescopes

A concept for testing a two-mirror telescope optical system and its optical components is proposed. The example of the space ultraviolet Ritchey-Chretien telescope, with a primary mirror of 170 cm diameter, is considered. The principal propositions of the concept, and the optical schematic diagrams of the independent and mutual testing of the primary and secondary telescope mirrors, are discussed. Constructional data are presented of optical testing systems, with a minimum number of auxiliary optical elements of simple configuration. When designing the optical testing system, the principle of the null test method has been used. According to this principle the object to be tested and the auxiliary optical elements form a system that is free of aberration for a given kind of ray path. This makes it possible to use various methods and instruments intended for testing aberration free optical systems, for example, Twyman-Green and Fizeau interferometers, Foucault or knife edge test, and star tests^1–4.     

激光干涉光刻法制作100 nm掩模

 介绍了一种利用激光干涉光刻技术得到特征图形,并通过离子束刻蚀将图形转移到铬层上,从而获得掩模的方法。针对掩模透光率以及对干涉图形对比度可能产生影响的两个参数分别进行了数值仿真,从而证明此方法的可行性和参数的优化选择。自搭干涉光刻实验系统,用257 nm的激光光源实现光刻,得到特征尺寸为100 nm的图形,再经过离子束刻蚀,最终得到周期200 nm、线宽100 nm的掩模。     

激光干涉光刻法制作100 nm掩模

介绍了一种利用激光干涉光刻技术得到特征图形,并通过离子束刻蚀将图形转移到铬层上,从而获得掩模的方法。针对掩模透光率以及对干涉图形对比度可能产生影响的两个参数分别进行了数值仿真,从而证明此方法的可行性和参数的优化选择。自搭干涉光刻实验系统,用257 nm的激光光源实现光刻,得到特征尺寸为100 nm的图形,再经过离子束刻蚀,最终得到周期200 nm、线宽100 nm的掩模。     

Periodic patterning using multi-facet prism based laser interference lithography

This paper discusses and present simple wavefront interference concept, using multi facet prisms and UV laser, to pattern periodic micro-features. Fabrication of square lattice features employing a biprism is illustrated. This concept is extended employing three facet prisms to fabricate hexagonal lattice structures. These micro-features are expected to find tunable photonic crystal applications. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

The RATAN-600 radio telescope as a two-mirror aplantatic system

We present the results of calculations for the characteristics of a RATAN-600 radio telescope in the radio-Schmidt telescope mode. The plane reflector and the principal antenna mirror were calculated as a two-mirror aplanatic system with a planoidal mirror for Schmidt correction of the wave front of the wave incident at an arbitrary angle to the horizon. Formulas were derived and codes were developed to calculate the configuration of the antenna-system mirrors and optimize the basic parameters of the system. It is shown that a long-term (up to one-hour) tracking of cosmic sources is possible in this operation mode at wavelengths greater than 2 and 4 cm for horizontal apertures of 100 and 150 m, respectively. Special Astrophysical Observatory of the Russian Academy of Sciences, Nizhny Arkhyz, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 3, pp. 185–196, March, 2000     

基于矢量波像差理论的两反光学系统装调研究

 为了实现对两反光学系统的精密装调,提出一种基于矢量波像差理论和波像差检测技术对失调量精确求解的装调方法。使用矢量波像差理论,将已设计的两反光学系统参数、失调量和失调光学系统的波像差之间建立方程;然后通过干涉测量法得到某一个视场的干涉图,利用条纹分析软件得到表征失调系统三阶彗差和三阶像散的泽尼克项系数,将泽尼克项系数代入方程从而求解出失调量。运用此方法对4 m口径RITCHEY-CHR-TIEN结构的天文望远镜进行模拟装调,最终求解的失调量与引入的失调量结果相互吻合,说明该装调方法正确。     

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.     

Three-dimensional photonic crystal of negative refraction achieved by interference lithography

A three-dimensional bicontinuous photonic crystal of a bcc lattice with all-angle negative refraction that can be achieved at optical frequencies by interference lithography is proposed. A numerical simulation of the focusing imaging of a slab of this crystal was performed to verify the property of all-angle negative refraction. The dependence of the negative-refraction frequency range on the threshold of photoresist development and on the dielectric constant is also discussed.