Electromagnetic modeling of near-field phase-shifting contact lithography with broadband ultraviolet illumination

Near-field phase-shifting contact lithography is modeled to characterize electromagnetic absorption in a photoresist layer with one face in contact with a quartz binary phase-shift mask. The broadband ultraviolet illumination is represented as a frequency-spectrum of normally incident plane waves. A rigorous coupled-wave analysis is carried out to determine the absorption spectrum of the photoresist layer. The specific absorption rate in the photoresist layer is calculated and examined in relation to the geometric parameters. Columnar features in the photoresist layer are of higher quality on broadband illumination in contrast to monochromatic illumination, in conformity with some recent experimental results. Feature resolution and profile are noticeably affected by the depth of the grooves in the phase-shift mask. Ideally, the feature linewidth can be less than about 100 nm for broadband illumination in the transverse-magnetic mode. These conclusions are subject to modification by the photochemistry-wavelength characteristics of the photoresist.     

激光光刻中焦深概念的新探讨

焦深大小将直接影响激光光刻加工的最细线宽和线条的边缘倾角从而影响被加工器件性能.传统的几何光学焦深概念对有光刻胶存在时的激光光刻已不适用.本文导出了会聚的高斯光束用于激光光刻时在光刻胶内的光场近似分布形式,由此可判断出光刻胶对光刻线条的分辨率和焦深的影响,从而提出激光光刻时焦深的新概念和估算.     

Far-field superlens for nanolithography

A far-field optical lithography is developed in this paper. By designing the structure of a far-field optical superlens, lithographical resolution can be improved by using a conventional UV light source. The finite different time domain numerical studies indicate that the lithographic resolution at 50~nm line width is achievable with the structure shown in this paper by using 365~nm wavelength light, and the light can be transferred to a far distance in the photoresist.     

Laser interference lithography using spray/spin photoresist development method for consistent periodic nanostructures

Generally, a simple immersion method for development of photoresist (PR) has been used to fabricate nanostructures by interference lithography (IL). However, the immersion method has the disadvantage that fabrication is inconsistent, especially for large-area periodic structures. Herein, we introduce the spray/spin PR development (SSPRD) method to fabricate periodic nanostructures using IL. By quantitative analysis and comparison, we characterized the effectiveness of the SSPRD method to develop PR. In our experiments the SSPRD method produced reliable uniform nanostructures, whereas the immersion method showed very poor consistency. In the SSPRD, rotation speed was very important: if it was too low the development speed differed between edges and center; if the rotation speed was too high it caused a distortion of nanostructures by unstable local flow induced by spraying and rotation So, to reduce this distortion, we adopted the puddle developing process; as a result the uniformity and repeatability of developed nanostructures were improved. These results demonstrate that the SSPRD method can be useful for fabrication of consistent periodic nanostructures.     

极紫外光刻离轴照明技术研究

离轴照明技术(OAI)是极紫外光刻技术中提高光刻分辨率的关键技术之一。为了实现考虑掩模阴影效应情况下离轴照明的优化选择,构造了一种新型实现OAI曝光的成像模型。将照射到掩模上的非相干光等效为一系列具有连续入射方向的等强度平行光,基于阿贝成像原理分别对掩模进行成像,最终在像面进行强度叠加实现OAI方式下空间成像的计算;并通过向投影系统函数添加离焦像差项实现不同离焦面上空间成像计算。该模型极大地简化了OAI条件下对掩模阴影效应的计算,提高了成像质量计算效率。结合光刻胶特性及投影曝光系统焦深设计要求,以显影后光刻胶轮廓的侧壁倾角为判据,获得了采用数值孔径为0.32的投影系统实现16 nm线宽黑白线条曝光的最优OAI参数。     

浸没式光刻投影物镜光学薄膜

深紫外光刻是目前集成电路制造的主流方法,为实现更小的元件特征尺寸,必须采用浸没式投影物镜以提高光学系统的分辨率,由此向其中的薄膜光学元件提出了众多苛刻的要求。本文介绍了适用于浸没式光刻系统的薄膜材料及膜系设计,以及高NA光学系统所需的大角度保偏膜系;对物镜中最关键的浸液薄膜的液体环境适应性、疏水及防污染等关键问题进行了讨论;对衡量浸没式光刻系统性能的重要因素镀膜元件激光辐照寿命,尤其是浸液环境下的元件辐照寿命进行了分析。     

同步辐射激发直接干化学刻蚀

同步辐射激发直接光化学刻蚀是近年来发展的一项新技术 ,它不需要常规光刻中的光刻胶工艺 ,用表面光化学反应直接将图形写到半导体材料的表面上。由于所用的同步辐射在真空紫外 (VUV)波段 ,理论上的分辨率可以达到电子学的量子极限 ,且没有常规工艺中的表面损伤和化学污染 ,是一种非常具有应用潜力的技术。本文的最后部份重点讨论了与上述技术密切相关的VUV和软X射线激发的表面光化学反应机理。     

复杂网络上动力系统同步的研究进展Ⅱ——如何提高网络的同步能力

本文在上一篇综述的基础上,详细介绍了2005年以来复杂网络上动力系统同步研究的最新进展,特别着重于如何提高网络同步能力方面的研究。文章首先介绍了最近有关网络结构与同步能力之间细致关系的研究,然后重点介绍了提高复杂网络同步能力的两种方法:调节耦合强度和改变网络结构,文章最后回答了上一篇综述提出的几个问题,并指出了这一领域几个新的有待解决的问题和可能的发展方向。     

一种可移动超分辨成像系统的制备及其性质研究

基于浸没透镜设计了一种超分辨成像系统,利用SU-8光刻胶和直径为4.87 m的微球实现纳米级别的超分辨成像。介绍微球成像放大率的求解方法,并通过软件模拟了超分辨成像系统的焦距。通过改变SU-8胶的厚度（从3.4 m到0）,系统的放大率也随之改变（放大率从1.6x到2.6x）。实验表明:SU-8胶的厚度对微球放大率有直接影响,通过该系统可以在普通光学显微镜下观察到蓝光光碟条纹。     

激光直写光刻中线条轮廓的分析

考虑了光刻胶对光吸收作用,在已有描述胶层内光场分布模型的基础上,较为准确地推导出光刻胶层内不同深度位置的光场分布.使用迭代方法计算得到了胶层内曝光量空间分布曲线,分析了不同曝光量下胶层内的线条轮廓,为直写光刻中曝光量的选择提供了依据.实验结果分析与理论分析的结果一致.     

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.     

球面旋涂光刻胶膜厚分布的数学模型

提出了球面旋涂微米级厚度光刻胶膜层薄化率公式及径向位置演变公式,并得到了膜厚分布的演变公式。与平面涂胶相比,球面涂胶离心力及重力分量是在不断的变化。根据平面旋涂运动方程及球面面形特征,给出了球面旋涂运动方程;结合流体层流的表面条件及不可压缩流体的质量连续方程,推导出了膜厚h及径向位置r对时间t的演变公式,并得到了在径向位置r处初始厚度为h0的膜厚演变的数学模型。通过对模型参数的分析可知,球面旋涂光刻胶应采用主从轴偏心旋涂,旋涂时工件的开口应朝向侧面(旋转轴水平)。     

Design and analysis of the single-step nanoimprinting lithography equipment for sub-100 nm linewidth

Nanoimprint lithography (NIL) is the cutting-edge technology to produce sub-100 nm scale features on substrates. The fundamental procedure of nanoimprint lithography is replicating the patterns defined in the stamp to any deformable materials such as photoresist spun on substrates by pressing and the physical shape of the resist is deformed during the imprinting process. In this study, for the single-step nanoimprinting process, the 4-in. imprinting head, the fabricated 4-in. mask, the alignment system for multi-layer processes, and the six-DOF compliant mechanism of a wafer stage for single-step nanoimprinting on a 4-in. wafer are proposed. Using the designed nanoimprinting equipment, the nanoscale patterns with 100 nm linewidth and 150 nm height were clearly patterned on the substrate. Finally, the nanoimprinting results show the validity of the developed equipment.     

大面积金纳米线光栅的制备

利用激光干涉光刻和金纳米颗粒胶体溶液制备了宽度在100 nm以下且总面积达到平方厘米量级的金纳米线光栅结构.制备过程中,首先在表面镀有厚度约为200 nm的铟锡氧化物薄膜的面积为1 cm×1 cm的玻璃基片表面旋涂光刻胶,然后利用紫外激光干涉光刻制备光刻胶纳米光栅结构.有效控制干涉光刻过程中的曝光量、显影时间,获得小占空比的光刻胶光栅.再以光刻胶纳米光栅作为模板,旋涂金纳米颗粒胶体溶液.充分利用金纳米颗粒胶体溶液在光刻胶表面浸润性差的特点,限制旋涂后留存在光刻胶光栅槽中金纳米颗粒的数量,从而达到限制金纳米线宽度的目的.最后在250℃将样品进行退火处理5 min.获得了周期为400 nm且占空比小于1:4的金纳米线光栅结构,其有效面积为1 cm².以波导共振模式与粒子等离子共振模式间耦合作用为特征的光谱学响应特性验证了波导耦合金属光子晶体的成功制备,为小传感体积新型生物传感器的开发提供了性能良好的金属光子晶体芯片.     

The three-dimensional photonic crystals coated by gold nanoparticles

We report on the fabrication of metallodielectric photonic crystals by means of interference lithography and subsequent coating by gold nanoparticles. The grating is realized in a SU-8 photoresist using a He-Cd laser of wavelength 442 nm. The use of the wavelength found within the photoresist low absorption band enables fabricating structures that are uniform in depth. Parameters of the photoresist exposure and development for obtaining a porous structure corresponding to an orthorhombic lattice are determined. Coating of photonic crystals by gold nanoparticles is realized by reduction of chloroauric acid by a number of reductants in a water solution. This research shows that the combination of interference lithography and chemical coating by metal is attractive for the fabrication of metallodielectric three-dimensionally periodic microstructures.     

基于数字微反射镜灰度光刻的成像模型

在深入探讨DMD(Digital Mirror Device)灰度图形传递的特点基础上，把曝光量分布作为分析数字光刻成像的物理量，建立了数字灰度光刻的成像模型.以制作微米量级微透镜为例，通过模拟分析，讨论了数字光刻过程中DMD的工作方式、成像系统参量对抗蚀剂曝光量分布的影响，揭示了数字灰度光刻成像机理，为开展数字光刻实验研究提供了理论根据.     

一种二元光学元件阵列微芯模的工艺设计研究

提出一种二元光学元件微型芯模的工艺设计方法,该方法利用了数字调制器件（DMD芯片）的空间光调制特性。首先通过编程设计出二元光学器件的相关软件,以实现菲涅耳透镜、达曼光栅、龙基光栅等各种矢量图形,经过14倍精缩光学系统,将由DMD芯片生成的二元光学器件图像成像在涂有光刻胶的基板上。经显影、定影和坚膜后,再利用电化学蚀刻,得到一种二元光学阵列的微芯模。这种二元光学的芯模制作方法可以方便、高效、低成本地用于制作微光学器件。     

Influences of water on photoresist surface in immersion lithography technology

In this study, we evaluated the influence of photoresist-water contact time on the quantity of the photoacid generator (PAG) leached from photoresists into pure water and alteration of the photoresist composition using LC-MS, XPS, and TOF-SIMS, by employing exposed and unexposed photoresists. As a result, the quantity of PAG leached into pure water increased as the contact time elapsed. Then, it was observed by TOF-SIMS that the quantity of the PAG on the photoresist surface decreased as the contact time elapsed. Regarding the ratio of the functional groups on the photoresist surface, the methyladamantyl group decreased but the carboxyl group increased because of exposure, respectively. On the exposed photoresist surface, the methyladamantyl group increased as the contact time elapsed. This was strongly related to the phenomenon that the quantity of methyladamantyl group was different between the inside and surface of photoresist.     

激光光刻中的超分辨现象研究

激光光刻是加工微光学及二元光学掩模的主要手段。光刻的最细线宽对所加工的二元微器件性能起决定作用。本文导出了会聚的高斯光束用于激光光刻时在光刻胶内的光场近似上此可判断出能光刻线条的分辨力。若入射高斯光束受到振中相位调制时,胶层内的光强分布将发生变化,从而影响曝光线条的线宽和质量。计算看出：当入射光中心环受到遮拦时,可以得到超光刻物镜极限分辨的线条宽度（０．６μｍ）,但此时对曝光能量控制要求很高。在激     

Research on the optical field distribution and micro-fabrication model in convex-surface laser lithography

A system of convex-surface laser lithography with diode laser is established in this paper. Based on this system, a mathematical model of optical field distribution and lithography on the photoresist layer of convex-surface substrate with diode laser is presented. According to the lithography system and model, some numerical simulations are carried out. The simulation result shows that lithographic lines on convex-surface lithography are not symmetric about the optical axis of incident laser beam. Axis of lines at different vector radius on convex-surface substrate will offset from the wavefront normal of incident laser beam. The offset distance depends on the slopes of different equivalent slants. The simulative results of lithographic model agree well with the lithographic experimental data.