355nm激光曝光SU-8胶的XPS谱和FT-IR谱研究

SU-8光胶因具有良好的光刻性能,并可获得稳定的高深宽比而在微加工领域得到了广泛的应用。众多研究采用不同的光源对其进行了多种光刻研究,本文应用355nm激光对SU-8胶进行曝光,分别采用XPS谱和FT-IR谱分析了SU-8胶与激光相互作用过程中,355nm激光对SU-8胶的作用以及反应前后主要成分含量、分子结构的变化,初步探讨了SU-8胶中激光曝光能量与透入深度的关系。     

SU-8光刻胶应变分布光学全场检测方法

由于SU-8光刻胶的内应力将会影响高深宽比结构的全金属光栅的制作质量,本文针对近年来SU-8光刻胶应力测量困难的情况,提出了一种基于激光剪切散斑干涉技术的SU-8光刻胶应变分布测量的新方法。该方法通过对被测胶体加载前后两幅干涉图像的处理,直接得到被测胶体结构的全场应变分布情况,由胶体的应变变形数据即可反映出内应力的变化和分布趋势。同时使用ANSYS有限元分析软件对同一被测胶体进行应变仿真模拟研究,获得胶体结构的变形场仿真数据。组建了实验系统,进行了实验验证,结果表明:实际测量变形量约为1.189μm,仿真的最大变形量为1.088μm,测量误差在允许范围内,且测量的形变趋势与仿真模拟结果相一致,表明激光剪切散斑干涉技术可应用于SU-8光刻胶的应变分布全场无损检测。     

Spiral three-dimensional photonic crystals for telecommunications spectral range

Three-dimensional photonic crystals consisting of periodic arrays of spiral columns were fabricated in a commercially available photoresist (SU-8) by a direct laser writing technique. Tailoring the pre- and post-processing conditions for the photoresist has enabled the recording of extended, self-supporting periodic structures with sub-diffraction resolution. Pronounced photonic stop gaps were observed at wavelengths between 1.5 and 1.8 μm, close to the telecommunications region. These structures can be used as accurate and robust templates for subsequent infiltration by materials with higher refractive index. PACS 42.65.Re; 42.70.-a; 42.70.Qs     

Silanization and antibody immobilization on SU-8

SU-8, an epoxy based negative photoresist, has emerged as a structural material for microfabricated sensors due to its attractive mechanical properties like low Young's modulus and chemical properties like inertness to various chemicals used in microfabrication. It can be used to fabricate MEMS structures of high aspect ratio. However, the use of SU-8 in BioMEMS application has been limited by the fact that immobilization of biomolecules on SU-8 surfaces has not been reported. In this study, the epoxy groups on the SU-8 surface were hydrolyzed in the presence of sulphochromic solution. Following this, the surface was treated with [3-(2-aminoethyl) aminopropyl]-trimethoxysilane (AEAPS). The silanized SU-8 surface was used to incubate human immunoglobulin (HIgG). The immobilization of HIgG was proved by allowing FITC tagged goat anti-human IgG to react with HIgG. This process of antibody immobilization was used to immobilize HIgG on microfabricated SU-8 cantilevers.     

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.     

Hollow tube fabrication in photoresist film using continuous wave laser

This paper is a study of three-dimensional (3D) micron/submicron fabrication with a continuous wave (CW) laser. The fabrication forms vertical and horizontal hollow tubes in a photoresist film with nonlinear optical properties. We controlled beam intensities and dose amounts to manipulate a reaction time constant of the photoresist; we fabricated the 3D hollows in high contrast.     

Fabricating high-aspect-ratio sub-diffraction-limit structures on silicon with two-photon photopolymerization and reactive ion etching

We fabricated sub-micrometer objects with feature sizes about one third of the exposure wavelength using two-photon photopolymerization in an epoxy-based photoresist SU-8 . Owing to the high mechanical strength of this photoresist, an aspect ratio as high as nine was achieved with a 200–300 nm lateral dimension. A simple equation was used to estimate the feature size from the laser parameters such as spot size, exposure time, pulse width, pulse repetition rate, and the material properties including the two-photon absorption coefficient and the exposure threshold dose. Patterns in SU-8 were transferred onto silicon using reactive ion etching, preserving both the feature size and aspect ratio. Vertical sidewalls of the transferred patterns were achieved using the black silicon method. PACS 42.82.Cr; 82.35.Ej; 85.40.Hp     

Laser fabrication of high-aspect-ratio holes and grooves in photoresist by time constant manipulation

We report on the cw-laser fabrication of sharp-edged holes and grooves in organic-dye-sensitized photoresists for g-line or i-line by manipulating its intensity and scanning rate. The laser fabrication is performed to locally control the reaction time constant of the photoresist. By scanning a tightly focused laser focal spot inside the transparent photoresist, various micron/submicron meter structures have been produced based on the reaction time constant depending on the beam intensity. The proposed method is considered to be a cost-effective technique for high-aspect-ratio holes and grooves fabrication.     

Design and fabrication of long focal length microlens arrays

In this paper, we present microlens arrays (MLA) with long focal length (in millimeter range) based on thermal reflow process. The focal length of microlens is usually in the same order of lens diameter or several hundred microns. To extend focal length, we made a photoresist (SU-8) MLA covered by a Polydimethylsiloxane (PDMS) film on a glass substrate. Because the refractive index difference between PDMS and photoresist interface is lower than that of air and MLA interface, light is less bended when passing through MLA and is focused at longer distance. Microlenses of diameters from 50 μm to 240 μm were successfully fabricated. The longest focal length was 2.1 mm from the microlens of 240 μm diameter. The numerical aperture (NA) was reduced 0.06, which is much lower than the smallest NA (~ 0.15) by regular thermal reflow processes. Cured PDMS has high transmittance and becomes parts of MLA without too much optical power loss. Besides, other focal lengths can be realized by modifying the refractive index different between two adjacent materials as described in this paper.     

Large-format fabrication by two-photon polymerization in SU-8

Microporous structures are central to many fields of science and engineering, but many of these systems are complex with little or no symmetry and are difficult to fabricate. We applied two-photon polymerization (2PP) and femtosecond laser direct-writing techniques to fabricate broad-area large-format 3D microporous structures (450 μm × 450 μm × 40 μm) in the epoxy-based photoresist SU-8. The appropriate exposure was determined by controlling average pulse energies and stage speeds to generate the exposure curves. Mechanical distortion exhibited in suspended walls fabricated by 2PP laser writing was studied by controlling wall lengths and widths. A simple thermal-expansion model is presented to explain the distortion caused by axial loadings of the walls.     

Self-organization in a chromium thin film under laser irradiation

Self-organization of chromium on glass was observed during laser ablation of the metal film with partially overlapping laser pulses. The beam of a nanosecond pulse laser tightly focused to a line was applied to the back-side ablation of the chromium thin film on a glass substrate. While the line ablated with a single laser pulse had sharp edges on both sides with ridges of the melted metal, the use of partially overlapping pulses formed a complicated structure made of the metal remaining from the ridges. Regular structures of ripples were developed in a certain range of laser fluence and pulse overlap. The ripple period could be controlled from 2.5 to 4 μm by variation of the processing parameters. Various experimental techniques were applied to test the structures, and different models of the ripple formation in the thin metal film were considered. The initial quasi-periodical formation started because of dewetting of thin liquid metal films on the glass substrate after its melting. Similar to the evaporation of liquid films, the small perturbation in the ridge thickness was able to induce instability in evaporation of the thin melted metal film. Freezing of the nonequilibrium state between laser pulses was one of the stabilizing factors in self-organization of the metal.     

掺半导体玻璃波导的导波功率限制

首次利用阳极氧化法在掺半导体玻璃上制备了两端带有抛物耦合喇叭的4微米条宽沟道波导,用光栅耦合器将波长0.532微米的YAG倍频激光耦合进波导中,实现了输出光的功率限制.     

Formation of two-dimensional periodic nanostructures on fused quartz,polyimide, and polycrystalline diamond by pulsed four-wave interference laser modification

Atomic force microscopy is used to examine the topography of submicron periodic structures formed on the surfaces of synthetic polycrystalline diamond and polyimide films. The films are deposited on fused quartz substrates by four-wave interference modification using a pulsed 308-nm UV XeCl excimer laser. It is demonstrated that a two-dimensional periodic relief with a submicron period can be formed on the diamond surface directly by laser evaporation in the absence of a photoresist. Depending on the exposure, two mechanisms of polyimide film modification are observed. At exposures less than 100 mJ/cm², the relief is formed due to swelling at the positions of interference maxima. At exposures greater than 100 mJ/cm², holes are formed in the films. A periodic relief on the fused quartz surface is formed by using a UV photoresist exposed to pulsed interference laser radiation and subsequent Ar ion etching.     

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。     

Interference nanolithography with a UV laser

The sensitivity and resolution of a photoresist composed of a two-layer (polymer-metallic indium) film are measured. 2D masks used to create nanodimensional metallic and insulating islands on a silicon substrate are prepared by direct laser action. Conditions are found for preparing submicron periodic structures on TiO₂ films that are applied on a glass substrate by the sol-gel technology. Optical properties of these arrays are measured, and it is shown that they can be used for exciting plane electromagnetic waves.     

Single-shot two-photon exposure of commercial photoresist for the production of three-dimensional structures

We report the use of an amplified femtosecond laser for single-shot two-photon exposure of the commercial photoresist SU-8. By scanning of the focal volume through the interior of the resist, three-dimensional (3-D) structures are fabricated on a shot-by-shot basis. The 800-nm two-photon exposure and damage thresholds are 3.2 and 8.1TW/cm(2), respectively. The nonlinear nature of the two-photon process allows the production of features that are smaller than the diffraction limit. Preliminary results suggest that Ti:sapphire oscillators can achieve single-shot two-photon exposure with thresholds as low as 1.6TW/cm(2) at 700 nm, allowing 3-D structures to be constructed at megahertz repetition rates.     

Using a micro-molding process to fabricate polymeric wavelength filters

A procedure for fabricating a high aspect ratio periodic structure on a UV polymer at submicron order using holographic interferometry and molding processes is described. First, holographic interferometry using a He–Cd (325 nm) laser was used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 20 nm nickel thin film was then sputtered on the photoresist. The final line pattern on a UV polymer was obtained from casting against the master mold. Finally, a SU8 polymer was spun on the polymer grating to form a planar waveguide or a channel waveguide. The measurement results show that the waveguide length could be reduced for the waveguide having gratings with a high aspect ratio.     

非对称光束干涉制备二维微纳光子结构研究

研究了基于不同偏振组合的非对称4束和5束光干涉制备二维微纳光子结构.通过改变光束的参数组合获得了枝节状、波形状等结构.在非对称光束干涉中,光束的构型和偏振改变了波矢差分布,从而改变晶格形貌和对比度.利用CHP-C感光胶开展了全息光刻实验制备,获得了与模拟一致的光子结构.该研究为制备新颖光子结构提供了有效途径,此类光子结构还可以为制备不同类型的金属点阵结构提供模板,对新型光子器件的制备和应用研究具有一定的促进作用.     

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     

Three-dimensional woodpile photonic crystal templates for the infrared spectral range

High-quality templates of three-dimensional woodpile photonic crystals are fabricated in photoresist SU-8 by use of femtosecond laser lithography. The samples have smooth surfaces, are mechanically stable, and are resistant to degradation under environmental and chemical influences. Fundamental and higher-order photonic stopgaps are identified in the wavelength range 2.0-8.0 microm. These templates can be used for subsequent infiltration by optically active or high-refractive-index materials.