Resolution and linewidth tolerances in electron beam and optical projection lithography

In order to understand the practical limits of electron beam direct-write and optical projection lithography techniques in device fabrication with micrometer and submicrometer geometries, we have exercised two computer simulation programs to estimate resolution limits and linewidth control. Latent image contrast and developed resist thickness contrast were calculated as a function of line-array spatial frequency. The linewidth tolerances were calculated by varying exposure, development time, focusing, line/space Pattern, resist thickness, etc. These simulation results indicate that the lithographic performance of the two techniques using state-of-the-art exposure tools are comparable at 1-µm dimensions. Some relevant experimental data also are presented.     

Technique for measurement of HCN-laser linewidth

The spectrum of the 311 and 337 ?m lines of an HCN laser is examined with a high-resolution spectrum analyser. Although the outputs have spectral widths of the order of 100kHz, the spectral width of the difference frequency is less than 5kHz. The observed spectra widths are caused by mechanical instability.     

Simulation and analysis for microstructure profile of optical lithography based on SU-8 thick resist

Profile simulation of optical lithography is very useful for micro-fabrication of microstructure with high sidewall quality. In this paper the light wave propagation, exposure and development process were analyzed, and modeling for thick film lithography was developed to accurately and rapidly obtain simulated results. The effect of exposure dose on the profile quality after development were simulated and discussed, which show that these process parameters have a great impact on the profile quality of microstructure. With guidance of the simulation and analysis, the micro-gear and micro-piston of micro-motor fabricated by SU-8 thick resist were presented.     

光学光刻中的离轴照明技术

本文讨论了光学光刻中的离轴照明技术。主要从改善光刻分辨率、增大焦深、提高空间像对比度等方面对离轴照明与传统照明作了比较 ,并用Prolith仿真软件进行了模拟分析。研究表明 ,离轴照明是一种很有效的光刻分辨率增强技术。     

Substrate-tube lithography for optical fibres

We describe the first use of substrate-tube lithography to build complex structures into MCVD fibre preforms. While the basic process is illustrated with high-birefringence fibres of 1.9 and 3 mm beat lengths and a two-core fibre, the technique is more general and may lead to a new class of integrated optical devices.     

New approach to resolution limit and advanced image formationtechniques in optical lithography

Practical resolution, the minimum feature size with a depth of focus (DOF) required for LSI fabrication process, is analyzed. Dependence of practical resolution on various factors, such as optical system parameters (exposure wavelength λ, and numerical aperture NA), resist processes, and required DOF, is investigated. It is shown that practical resolution in the sub-halfmicrometer region is not improved, and may even be degraded, with increasing NA. Furthermore, resolution improvement by increasing NA becomes less effective as λ becomes shorter. This means that the high-resolution capability of high-NA/short-wavelength optics cannot be utilized to create fine-pattern LSIs. In order to overcome this limitation, the effectiveness of advanced image formation techniques, the phase-shifting method and the FLEX method, in practical resolution enhancement is investigated. It is experimentally verified, using a phase-shifting mask and the excimer laser stepper, that a pattern feature size less than 0.2 μm can be clearly delineated with sufficient focus latitude. These advanced techniques make it possible to overcome the resolution limitation of conventional optical lithography     

Novel measurement method of linewidth enhancement factor in semiconductor lasers by optical self-locking

The authors propose a simple, accurate and novel method to measure the value of the linewidth enhancement factor in semiconductor lasers. It utilises the asymmetry of the frequency locking range of a semiconductor laser with the optical feedback from the external CFP cavity. The measured value for a 0.8 mu m CSP-type AlGaAs laser was 3.07+or-0.26, which showed good agreement with those measured by other conventional methods.<>     

采用序列图像的被动光学测速技术

在获取无人机等飞行器的飞行速度时,自主、隐蔽性好的测量技术具有重要的应用价值。提出了一种利用光学相机拍摄的地面景象进行飞行器速度测量的技术。文中详细阐述了该项技术的工作原理,利用同一景物在两幅有重叠区域的图像中的位移量及间隔时间计算飞行器的运动速度。并且分析了其中关键的图像匹配技术,采用SIFT算法获得抗旋转、尺度变化的稳定特征点。重点对测速精度的各个影响因素进行了理论分析,给出了利用多帧图像进行测速提高测速精度的方法,综合分析了速度测量中的误差来源和各影响因素。理论研究和分析结果表明:利用光学图像进行速度测算的方案正确,精度能够满足飞行器速度测量的要求。     

相干光纤通信系统对激光器线宽的要求

通过仿真相干光接收机载波相位估计性能,研究了采用不同调制格式时对所使用激光器线宽的要求,分析了16-QAM采用Star和Square两种不同星座图时线宽要求差异的原因.仿真结果表明:对于既定的比特速率,采用高阶调制格式的系统降低了线路符号速率,但要求激光器线宽更窄;同一调制格式对激光器线宽的要求与所采用的星座图有关.     

Electron image projection systems for microcircuit lithography

High-resolution electron-beam microfabrication requires long process times when using a single scanning beam to expose large-area integrated circuits. Exposure times for a 2-in wafer by a scanning beam system are typically between 30 min to 3 h, depending on the area and complexity of the circuit. This paper describes an electron projection system that projects the whole electron image of the integrated circuit mask onto the wafer at once, enabling exposure times of 1 s or less to be attained. The system incorporates a photocathode patterned into an integrated circuit mask. The pattern is projected and focused onto the wafer using axial magnetic and electrostatic fields. Described herein are factors affecting photocathode life and exposure times. A technique for automatic alignment of the mask to the wafer is also described which has achieved 0.25-µ alignment accuracies.     

Holographic measurement of refractive-index profile of optical fibre preform

A holographic method of measuring the refractive-index profile of an optical fibre preform is presented. It uses the principle of shearing interferometry. The method is simple and allows measurements to be repeated even after the preform has been withdrawn for fibre drawing.     

Nanoimprint lithography resist profile inversion for lift-off applications

A method is described in which the tapered features that are inherent to nanoimprint lithography are inverted to allow successful lift-off. A mold of the relief is created by in-filling the imprinted resist with hydrogen silsesquioxane (HSQ) before selectively removing the resist with O₂ plasma. Nanoscale etch masks have been created by lift-off from the negative HSQ profile and used to create high-aspect-ratio structures in materials that are hard to plasma etch.     

Delayed self-heterodyne linewidth measurement of VCSELs

We report on high-resolution linewidth measurements of proton-implanted InGaAs-GaAs VCSELs employing the delayed self-heterodyne method. Devices with 16-/spl mu/m active diameter exhibit record low linewidths of 20 MHz and 4-MHz residual linewidth. The linewidth enhancement factor is accurately determined from the ratio of induced phase to amplitude modulation indexes.     

Binary and phase shifting mask design for optical lithography

The authors propose a number of pre-distorted mask design techniques for binary and phase-shifting masks. Their approach is based on modeling the imaging mechanism of a stepper by the Hopkins equations and taking advantage of the contrast-enhancement characteristics of photoresist. Optimization techniques such as the branch and bound algorithm and simulated annealing algorithm are used to systematically design pre-distorted masks under incoherent and partially coherent illumination. Computer simulations are used to show that the intensity contour shapes and developed resist shapes of their designed mask patterns are sharper than those of conventional masks. The designed phase-shifting masks are shown to result in higher contrast as well as sharper contours than binary masks. An example of phase conflicting masks designed with the algorithm is shown to outperform a simple intuitive design. This example indicates that a fairly general design procedure consisting of alternating phase shifts and their optimized phase-shift masks is a viable candidate for future phase-shifting mask design     

光学光刻设备发展和展望

在半导体技术和制造的发展中,半导体加工技术中最为关键的光刻技术和光刻工艺设备,必将发生显著的变化,本文将对光刻技术和光刻设备的发展历史进行简述,并展望未来光刻技术的趋势.     

Nondestructive refractive-index profile measurement of elliptical optical fibre or preform

A nondestructive method of determining the refractive-index profile of an elliptic optical fibre or preform is reported. For the fibre, the pathlength data obtained from interference microscopic measurement are used. For the preform, the ray exit angles are used. These data are put into an integral that can be inverted numerically to obtain the reconstructed profile.     

基于图像的轮对踏面轮廓测量方法

轮对作为动车运行的重要部件,如果出现故障,将引发不可预想的后果,因此如何实时地、有效地、精确地检测车轮在列车众多安全问题中显得尤其重要。文中在使用非接触式检测车轮,通过CCD采集系统获得原始的轮对踏面曲线的基础上,通过图像降噪处理、曲线提取和曲线拼接一系列方法,实现获取车轮踏面完整轮廓。文中在曲线提取和拼接的算法部分,通过对比已有的方案和方法,提出了适合轮对踏面轮廓的改进算法并通过实验进行分析和验证。通过实验证明,文中提出的车轮踏面轮廓测量方法易于实现、适用范围广。     

几种测量超窄激光线宽方法的比较

介绍了布里渊光纤环形激光器拍频法、差拍法、零拍法和光纤环法4种超窄激光线宽的测量方法.通过比较,给出了4种方法在分辨率、激光线宽和线型效应等方面的优缺点,根据这些优缺点,指出了每种方法的适用范围.     

Two-dimensional optical mask design and atom lithography

Atom lithography is one of the latest proposals for high-resolution printing. The mask design and generation is key step for implementation of this method. In this paper, we have theoretically investigated and proposed a new method for two-dimensional optical mask design in atom lithography. A new method for realization of our proposed technique based on guided modes will present. With our proposed idea one can easily print every kind of two-dimensional patterns. This method can lead us to produce the nano-scale electronic and optical devices and systems. Also, a suitable algorithm for mask generation is proposed.     

温度气压对高分辨力光刻物镜像质影响研究

分析温度气压对物镜光学材料、透镜厚度间隔,以及空气折射率的影响,并用空气折射率对物镜像质影进行模拟计算。研究表明物镜焦面产生较大漂移,对僧率有一定影响,而对畸变影响较小,指出对物镜进行温度气压控制补偿是必要的。