Two-photon polymerization lithography for imaging optics

Optical imaging systems have greatly extended human visual capabilities,enabling the observation and understanding of diverse phenomena.Imaging technologies span a broad spectrum of wavelengths from x-ray to radio frequencies and impact research activities and our daily lives.Traditional glass lenses are fabricated through a series of complex processes,while polymers offer versatility and ease of production.However,modern applications often require complex lens assemblies,driving the need for miniaturization and advanced designs with micro-and nanoscale features to surpass the capabilities of traditional fabrication methods.Three-dimensional(3D)printing,or additive manufacturing,presents a solution to these challenges with benefits of rapid prototyping,customized geometries,and efficient production,particularly suited for miniaturized optical imaging devices.Various 3D printing methods have demonstrated advantages over traditional counterparts,yet challenges remain in achieving nanoscale resolutions.Two-photon polymerization lithography(TPL),a nanoscale 3D printing technique,enables the fabrication of intricate structures beyond the optical diffraction limit via the nonlinear process of two-photon absorption within liquid resin.It offers unprecedented abilities,e.g.alignment-free fabrication,micro-and nanoscale capabilities,and rapid prototyping of almost arbitrary complex 3D nanostructures.In this review,we emphasize the importance of the criteria for optical performance evaluation of imaging devices,discuss material properties relevant to TPL,fabrication techniques,and highlight the application of TPL in optical imaging.As the first panoramic review on this topic,it will equip researchers with foundational knowledge and recent advancements of TPL for imaging optics,promoting a deeper understanding of the field.By leveraging on its high-resolution capability,extensive material range,and true 3D processing,alongside advances in materials,fabrication,and design,we envisage disruptive solutions to current challenges and a promising incorporation of TPL in future optical imaging applications.

Fast source mask co-optimization method for high-NA EUV lithography

Extreme ultraviolet(EUV)lithography with high numerical aperture(NA)is a future technology to manufacture the integrated circuit in sub-nanometer dimension.Meanwhile,source mask co-optimization(SMO)is an extensively used approach for advanced lithography process beyond 28 nm technology node.This work proposes a novel SMO method to improve the image fidelity of high-NA EUV lithography system.A fast high-NA EUV lithography imaging model is established first,which includes the effects of mask three-dimensional structure and anamorphic magnification.Then,this paper develops an efficient SMO method that combines the gradient-based mask optimization algorithm and the compressivesensing-based source optimization algorithm.A mask rule check(MRC)process is further proposed to simplify the optimized mask pattern.Results illustrate that the proposed SMO method can significantly reduce the lithography patterning error,and maintain high computational efficiency.

Real-time generation of circular patterns in electron beam lithography

Electron beam lithography(EBL)involves the transfer of a pattern onto the surface of a substrate byfirst scanning a thin layer of organicfilm(called resist)on the surface by a tightly focused and precisely controlled electron beam(exposure)and then selectively removing the exposed or nonexposed regions of the resist in a solvent(developing).It is widely used for fabrication of integrated cir-cuits,mask manufacturing,photoelectric device processing,and otherfields.The key to drawing circular patterns by EBL is the graphics production and control.In an EBL system,an embedded processor calculates and generates the trajectory coordinates for movement of the electron beam,and outputs the corresponding voltage signal through a digital-to-analog converter(DAC)to control a deflector that changes the position of the electron beam.Through this procedure,it is possible to guarantee the accuracy and real-time con-trol of electron beam scanning deflection.Existing EBL systems mostly use the method of polygonal approximation to expose circles.A circle is divided into several polygons,and the smaller the segmentation,the higher is the precision of the splicing circle.However,owing to the need to generate and scan each polygon separately,an increase in the number of segments will lead to a decrease in the overall lithography speed.In this paper,based on Bresenham’s circle algorithm and exploiting the capabilities of afield-programmable gate array and DAC,an improved real-time circle-producing algorithm is designed for EBL.The algorithm can directly generate cir-cular graphics coordinates such as those for a single circle,solid circle,solid ring,or concentric ring,and is able to effectively realizes deflection and scanning of the electron beam for circular graphics lithography.Compared with the polygonal approximation method,the improved algorithm exhibits improved precision and speed.At the same time,the point generation strategy is optimized to solve the blank pixel and pseudo-pixel problems that arise with Bresenham’s circle algorithm.A complete electron beam deflection system is established to carry out lithography experiments,the results of which show that the error between the exposure results and the preset pat-terns is at the nanometer level,indicating that the improved algorithm meets the requirements for real-time control and high precision of EBL.

面向三重版图曝光约束的详细布线算法

在进一步缩小特征尺寸的问题上,三重版图曝光技术(triplepatterninglithography,TPL)发挥着重要的作用.针对TPL中的版图分解问题,提出了一种基于TPL约束的详细布线算法.将版图分解问题转化为满足同色间距约束和最小间距约束的详细布线问题,使用网格编码的方法来满足2种间距约束;利用与2种间距约束相结合的Hannan网格来提升布线资源的利用率以及布线的速度;结合多源迪杰斯特拉算法进行多端线网的最短路径搜索;最后将布线结果进行版图分解,实现最小化冲突数量和缝合点数量的目标.算法在2.20 GHzCPU和32 GB内存的Ubuntu20.04环境下运行,使用2018年ISPD详细布线比赛的测试集.实验结果表明,与普通详细布线相比,可降低约60%的冲突数量以及70%的缝合点数量.

MOA框架下关键核心技术突破路径研究——以光刻技术领域为例

[研究目的]识别关键核心技术突破路径,加快实现科技自立自强对维护我国产业链供应链安全具有重要的现实意义。[研究方法]基于组织行为视角,通过MOA(动机-机会-能力)分析框架厘清7个变量作为企业突破关键核心技术的前因条件。在此基础上,考虑到我国光刻技术领域的阶段性特征,选取35家光刻技术领域的上市企业为研究对象,并采用NCA和fsQCA方法,分追赶、跟随和攻坚三阶段识别关键核心技术突破路径。[研究结论]机会感知能力是企业加快实现关键核心技术突破的必要条件,且政府支持发挥了普适作用。三阶段共存在7条突破路径,概括为四种驱动类型:追赶阶段的动机-政府-吸收能力驱动型、感知能力驱动型;跟随阶段的政府-吸收能力驱动型;攻坚阶段的政府-适应能力驱动型。突破路径在三阶段间存在演变现象,形成三种演变轨迹包括“缓冲主导轨迹”“转折轨迹”和“主导轨迹”。

从抄配、借校到石印:徐乃昌刊印《说文解字韵谱》考

徐乃昌1925年自来青阁购得元种善堂本《说文解字韵谱》后,拟覆刻出版。徐乃昌请范兆经据《函海》本、李显本抄补缺叶缺字,又先后拟请黄侃、刘葆儒撰写校记,惜校记未能完成。最终,徐乃昌以自藏本《韵谱》为主要底本,又借瞿启甲所藏同版但较为晚印之《韵谱》配补缺叶,于1927年交鸿宝斋石印出版。徐乃昌的书籍出版,在《说文解字韵谱》之后,逐渐从雕版转向石印。梳理徐乃昌刊印《韵谱》的前后始末,也有助于推进对20世纪20年代沪上古籍出版情况的认识。

基于光纤传感航天器神经网络与数字孪生研究

文中设计了一种掺杂Al_(2)O_(3)、Y_(2)O_(3)、P_(2)O_(5)的新型石英光纤,制作的光纤成品纤芯折射率类线性分布。通过飞秒激光直写技术,在光纤上刻写出光纤Bragg光栅,制作出光栅串。将多根光栅串布设在航天器卫星模型上,形成航天器智能蒙皮,用于感知卫星结构损伤状态。基于上述测量数据,使用unity3D软件开发航天器的3D模型及相匹配的python程序对数据进行处理,实现航天器的数字孪生和状态感知。进一步通过模型建立和BP神经网络算法对传感数据进行感知训练,模型对撞击信号的预测准确率高达90%。

A Kernel-Based Convolution Method to Calculate Sparse Aerial Image Intensity for Lithography Simulation

Optical proximity correction (OPC) systems require an accurate and fast way to predict how patterns will be transferred to the wafer.Based on Gabor's 'reduction to principal waves',a partially coherent imaging system can be represented as a superposition of coherent imaging systems,so an accurate and fast sparse aerial image intensity calculation algorithm for lithography simulation is presented based on convolution kernels,which also include simulating the lateral diffusion and some mask processing effects via Gaussian filter.The simplicity of this model leads to substantial computational and analytical benefits.Efficiency of this method is also shown through simulation results.

A New Method to Retrieve Proximity Effect Parameters in Electron-Beam Lithography

A new method for determining proximity parameters α,β ,and η in electron beam lithography is introduced on the assumption that the point exposure spread function is composed of two Gaussians.A single line is used as test pattern to determine proximity effect parameters and the normalization approach is adopted in experimental data transaction in order to eliminate the need of measuring exposure clearing dose of the resist.Furthermore,the parameters acquired by this method are successfully used for proximity effect correction in electron beam lithography on the same experimental conditions.

具有双重显影特性的多用途单分子树脂化学放大光刻胶

化学放大光刻胶(CARs)由于其在分辨率和灵敏度方面的出色性能而广泛应用于光刻领域。本文报道了一种基于单分子树脂的多用途化学放大光刻胶SP8-PAG_(AN),可同时用于365 nm光刻和电子束光刻。该体系主要由螺二芴结构的单分子树脂主体材料(SP-8Boc)和N-(三氟甲基磺酸酯基)蒽-1,9-二羧酰亚胺非离子型光致产酸剂(PAGAn)组成。测试了产酸剂PAGAN在365 nm紫外光激发下的光致产酸效率ΦH+为23%。研究了SP8-PAG_(AN)光刻胶的365 nm光刻和电子束光刻性能。365 nm光刻中,分别利用四甲基氢氧化胺(TMAH,质量分数2.38%)水溶液和正己烷作为显影液,可实现1μm正性和负性光刻图案。电子束光刻中,可实现50 nm Line/Space(L/S)的正性密集线条图案(曝光剂量110μC/cm^(2)),32 nm L/S的负性密集线条图案(曝光剂量40μC/cm^(2))以及19 nm L/3S负性半密集线条图案(曝光剂量96μC/cm^(2))。本研究工作提供了一种具有双重显影特性的多用途单分子树脂化学放大光刻胶的新范例。

Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror

Particle-In-Cell(PIC)simulations were performed in this work to study the dynamics of the EUVinduced hydrogen plasma.The Monte-Carlo Collision(MCC)model was employed to deal with the collisions between charged particles and background gas molecules.The dynamic evolution of the plasma sheath,as well as the flux and energy distribution of ions impacting on the mirror surface,was discussed.It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium mirror coating creates a positively charged wall and then prevents the ions from impacting on the mirror and therefore changes the flux and energy distribution of ions reaching the mirror.Furthermore,gas pressure has a notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors.With greater gas pressure,the sheath potential decreases more rapidly.The flux of ions received by the mirror grows approximately linearly and at the same time the energy corresponding to the peak flux decreases slightly.However,the EUV source intensity barely changes the sheath potential,and its influence on the ion impact is mainly limited to the approximate linear increase in ion flux.

Patterning single-layer materials by electrical breakdown using atomic force microscopy

The development of nanoelectronics and nanotechnologies has been boosted significantly by the emergence of 2D materials because of their atomic thickness and peculiar properties,and developing a universal,precise patterning technology for single-layer 2D materials is critical for assembling nanodevices.Demonstrated here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores,nanostrips,and other nanostructures on demand.This can be achieved by voltage scanning or applying a constant voltage while moving the tip.By measuring the electrical current,the formation process on single-layer materials was shown quantitatively.The present results provide evidence of successful pattern fabrication on single-layer MoS2,boron nitride,and graphene,although further confirmation is still needed.The proposed method holds promise as a general nanomachining technology for the future.

Design and tailoring of patterned ZnO nanostructures for perovskite light absorption modulation

Lithography is a pivotal micro/nanomanufacturing technique,facilitating performance enhancements in an extensive array of devices,encompassing sensors,transistors,and photovoltaic devices.The key to creating highly precise,multiscale-distributed patterned structures is the precise control of the lithography process.Herein,high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography.By optimizing these parameters,ZnO nanorod arrays with line/hole arrangements are successfully prepared.Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure,enlarged surface area,and improved light capture ability,which achieve highly efficient energy conversion in perovskite solar cells.The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.

基于掩模光刻的液晶波前校正器设计与制备

液晶波前校正器通常基于液晶显示器的工艺制备而成,因此其研制成本高、定制难度大。本文基于掩模光刻法制备液晶波前校正器,以实现液晶波前校正器的专用化、低成本研制。基于掩模光刻技术设计并制备了91像素的无源液晶驱动电极,并封装成液晶光学校正单元。设计并制备了驱动连接电路板,实现了液晶光学驱动单元和驱动电路板的匹配对接。对液晶波前校正器响应特性进行检测。结果显示,其相位调制量为5.5个波长,响应时间为224 ms。利用Zygo干涉仪进行球面波的产生和静态倾斜像差的校正。结果显示,其可以产生正负离焦波前,且对水平倾斜像差校正后,Zernike多项式中第一项的值从1.18降至0.16,校正幅度达86%,实现了像差的有效校正。本文的研究工作可为液晶波前校正器的研制提供新思路,进而拓宽其应用领域和场景。

The study of lithographic variation in resistive random access memory

Reducing the process variation is a significant concern for resistive random access memory(RRAM).Due to its ultrahigh integration density,RRAM arrays are prone to lithographic variation during the lithography process,introducing electrical variation among different RRAM devices.In this work,an optical physical verification methodology for the RRAM array is developed,and the effects of different layout parameters on important electrical characteristics are systematically investigated.The results indicate that the RRAM devices can be categorized into three clusters according to their locations and lithography environments.The read resistance is more sensitive to the locations in the array(~30%)than SET/RESET voltage(<10%).The increase in the RRAM device length and the application of the optical proximity correction technique can help to reduce the variation to less than 10%,whereas it reduces RRAM read resistance by 4×,resulting in a higher power and area consumption.As such,we provide design guidelines to minimize the electrical variation of RRAM arrays due to the lithography process.

光栅干涉式触觉传感器

因光学式触觉传感器有着灵敏度高、抗干扰能力强等优点,提出了一种基于亚波长金属光栅干涉的触觉传感器。首先,基于等效介质理论和薄膜干涉理论对触觉传感器的传感原理进行介绍;接着,通过纳米压印工艺和真空蒸发镀膜工艺在柔性中间聚合物片材(IPS)表面制作亚波长金属光栅,通过光刻工艺用SU—8光刻胶将亚波长金属光栅以固定间距平行离面放置,使其透射光强随接触力的施加而改变;最后,对光栅触觉传感器进行一系列力加载实验,实验结果表明:该触觉传感器的平均力分辨率可达到0.0003N/Gray以上,平均测量误差为6.3%。通过小型化设计,可以用于机械手上实现触觉传感功能。

Fabrication of Silicon Crystal-Facet-Dependent Nanostructures by Electron-Beam Lithography

Silicon crystal-facet-dependent nanostructures have been successfully fabricated on a （100）-oriented silicon-oninsulator wafer using electron-beam lithography and the silicon anisotropic wet etching technique. This technique takes advantage of the large difference in etching properties for different crystallographic planes in alkaline solution. The minimum size of the trapezoidal top for those Si nanostructures can be reduced to less than 10nm. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） observations indicate that the etched nanostructures have controllable shapes and smooth surfaces.

Nano-Level Electron Beam Lithography

The JEOL JBX-5000LS is a vector type machine.The system hardware features an ion-pumped column,a LaB 6 electron emitter,25kV and 50kV accelerating voltage,and a turbo-pumped sample chamber.The resolution,stability,stitching and overlay of this system are evaluated.The system can write complex patterns at dimensions down to 30nm.The demonstrated overlay accuracy of this system is better than 40nm.

基于101.6 mm晶圆35 nm InP HEMT工艺的340 GHz低噪声放大器芯片研制

实现了在101.6 mm InP晶圆上制备35 nm的增强型InP高电子迁移率晶体管。通过InAs复合沟道外延结构设计,使得室温二维电子气迁移率面密度乘积达到4.2×10^(16)/(V·s)。采用了铂钛铂金埋栅工艺技术,典型器件最大跨导达到2900 mS/mm,电流增益截止频率达到460 GHz,最高振荡频率为720 GHz。同时研制出340 GHz低噪声放大器芯片,在310~350 GHz内小信号增益22~27 dB,噪声系数在8 dB以下。建立了340 GHz InP低噪声放大器芯片技术平台,为太赫兹低噪声单片微波集成电路的发展奠定基础。

微型阵列束闸设计与实验

微型阵列束闸是多束电子束曝光系统的关键部件,用于控制多束电子束的开/关,实现复杂图形的快速曝光。对3×3微型阵列束闸进行了设计与制作,并进行了多束电子束偏转实验研究。对阵列束闸结构进行了优化设计,并基于MEMS加工工艺成功制备了阵列束闸。针对阵列束闸的控制要求,设计了可单独控制的阵列束闸控制器。将控制器与阵列束闸进行连接,验证了控制器的偏转速度与功能完整性。最后,在多束电子束测试平台对阵列束闸进行了偏转实验,研究串扰对电子束偏转的影响。实验结果表明:阵列束闸控制器的偏转速度达到43.5 MHz,大于设计值10 MHz;阵列束闸成功实现了单独控制电子束开和关,束闸的偏转距离在25~30μm之间,小于计算值43.29μm;串扰程度均小于3%。该阵列束闸已经具备多束电子束开/关控制功能,但在偏转精度,设计和加工工艺等方面还需进一步优化和完善。