UV-LIGA技术制作微型螺旋形加速度开关

微型加速度开关是用于空间飞行体中感受加速度并完成致动的重要惯性器件。本文采用UV-LIGA技术,结合SU-8厚胶工艺、微电铸工艺以及牺牲层技术,制作了微型螺旋形加速度开关。研究了牺牲层工艺、SU-8光刻技术以及螺旋形弹簧形变控制等微细加工的工艺细节;分析了多种牺牲层材料的特性,优选了与工艺相适应的Zn牺牲层体系,解决了微结构易脱落的工艺问题。通过优化微电铸工艺来减小金属膜层的内应力,优化牺牲层释放工艺来避免腐蚀过程对弹簧膜结构的冲击。实验结果表明,通过工艺优化可得到平整的微型螺旋形弹簧—质量块结构,螺旋弹簧厚度为20μm,质量块厚度达200μm,本文的工作可为大批量、低成本地研制微型加速度开关提供工艺基础。     

Direct fabrication of deep x-ray lithography masks by micromechanical milling

Micromechanical milling has been shown to be a rapid and direct method for fabricating masks for deep x-ray lithography with lateral absorber features down to 10 micrometers. Conventional x-ray mask fabrication requires complex processes and equipment, and a faster and simpler method using micromechanical milling was investigated for larger microstructures for mesoscale applications. Micromilled x-ray masks consisting of a layered architecture of gold and titanium films on graphite yielded exposures in PMMA with accuracy and repeatability suitable for prototype purposes. A method for compensating milling tool radial runout was adapted, and the average accuracy of mask absorber features was 0.65 micrometers, with an average standard deviation of 0.55 micrometers. The milling process leaves some absorber burrs, and the absorber wall is tapered, which introduces an additional process bias. Mask fabrication by micromilling is fast and, therefore, less costly than conventional mask fabrication processes.     

X光光刻工艺微针阵列的制备、测试和仿真

为了提高透皮给药的效率,降低传统注射对人体的疼痛感,需要制备微针阵列结构。本文介绍了一种新的微针阵列结构的制造技术。利用日本立命馆大学的同步辐射光源AURORA进行两次X光移动光刻和一次固定X光光刻技术,在PMMA光刻胶上得到微针阵列。通过采用不同的掩膜版图形以及对不同位置的空心孔进行X光光刻,获得了不同规格的空心微针阵列,针对固定X光光刻时对准的问题,自行研制了X光光刻对准装置,实验结果证明,该装置能实现空心微针阵列的制备。并且进行了微针刺穿测试,结果证明微针有足够的强度。为了达到低成本批量复制微针阵列的目的,还进行了微针模具的倒模和复制实验,成功得到金属镍实心微针阵列。最后,针对光刻过程中微针阵列结构的侧面形状发生畸变的情况,对移动X光光刻建立了仿真预测,将仿真预测结果与实验结果进行了比较,结果表明显影深度的误差为5%。     

LIGA技术基础研究

阐述了LIGA技术的组成及特点.对LIGA工艺掩膜、X射线光刻、电铸及塑铸等进行了工艺原理分析.用一次成型法制作了以聚酰亚胺为衬基、以Au为吸收体的X射线光刻掩膜.简单介绍了这种掩膜的制作工艺过程,并用这种掩膜在北京电子对撞机国家实验室进行了同步辐射X射线光刻,得到了深度为500μm,深宽比达8.3的PMMA材料的微型电磁马达联轴器结构.给出掩膜和X射线光刻照片.同时,对Au、Ni等金属材料的厚膜电铸进行了工艺研究.     

Applications of focused ion beams

A finely focused ion beam system is described. Beams of Ga, In, and Au ions emitted from a liquid metal ion source are routinely focused to spot diameters of ∼0.1 to 3.0 μm at a current density of ∼0.5 A/cm² and a beam energy of 20 keV. Focused beams with energies of 1 to 30 keV have also been produced. Three applications are discussed: (1) scanning ion microscopy, (2) mask repair, and (3) ion beam lithography. Scanning ion images illustrating topographic and chemical contrast are presented. The repair of opaque and clear defects in optical masks, and opaque defects in X-ray masks is shown.Defects are imaged with the ion beam and removed by sputter erosion. Edge reconstruction of 0.5 μm features is demonstrated. Most repairs take less than 10 s/μm². The advantages and limitations of ion beams for lithography are discussed.     

Fabrication of suspended micro-structures using diffsuser lithography on negative photoresist

We report the results of diffuser lithography applied to a negative-type thick photoresist to fabricate 3-dimensional microstructures suspended on supports. When UV light passes through a diffuser film, the direction of the light is randomized because of the irregular surface of the diffuser. By exposing through a diffuser on a Cr-mask, a circular or an elliptical cross-section of exposed region can be formed on a spin-coated photoresist. When applied to a negative-type thick photoresist, diffuser lithography gives a 3-dimensional circular cross-section of the exposed and cross-linked regions, which could be used for making suspended microstructures. The size of the exposed region has been controlled by the dose of the UV light. The current study clearly shows that the depth of exposed region of photoresist is affected by the geometry of the pattern. By controlling the depth of the exposed region using different pattern size, beam structures suspended on the support structures could be fabricated by single exposure process. The characteristics of the diffuser lithography process were investigated on a negative type photopolymer, SU-8, with different doses of UV-light and different geometry.     

同步辐射X射线光刻掩模镀金工艺的研究

介绍了利用北京正负对撞机(BEPC)同步辐射X射线光刻装置,进行LIGA工艺技术深结构光刻实验研究,详细论述了X射线光刻使用的掩模制备过程及掩模镀金工艺,在国内最早曝光出直径为400μm、厚为27～45μm的三维立体齿轮胶图形。     

Imprinting a needle array on a polycarbonate substrate

A micro-needle array was fabricated on a polycarbonate (PC) substrate using an electroformed-Ni mold with a conical concave pattern. The diameter and length of each needle were 50 μm and 135 μm, respectively. The needle array pattern of the electroformed-Ni mold was produced by combining a grayscale mask for X-ray lithography with Ni electroforming technology. The X-ray grayscale mask was composed of Si absorbers and a SU-8 membrane. Each Si absorber had a three-dimensional cone shape rather than a rectangular shape. Threedimensional Si structures were formed to etch an active Si layer in a silicon-on-insulator wafer using a taperedtrench etching technology. Beamline BL-4 in the TERAS synchrotron radiation facility at AIST was used for the Xray lithography experiments. X-rays that penetrated the X-ray grayscale mask irradiated a polymethylmethacrylate (PMMA) sheet. Pt was deposited on the PMMA structure after developing, and Ni was electroformed on it. The electroformed-Ni object was processed by grinding to complete a Ni mold. Finally, the micro-needle array was fabricated by thermal-imprinting on a 0.5-mm thick PC sheet with the electroformed Ni mold.     

Formation of Thick High-Aspect-Ratio Resistive Masks by the Contact Photolithography Method

A method of fabrication of thick (~100 μm and more) resistive masks is described. These masks can be used for solving various engineering problems, e.g., for fabricating x-ray-absorbing topological patterns for LIGA masks, stamp microrelief, cast moulds, etc. Specific features of the contact photolithography method, which is used to design and fabricate the research device, are described. A source of exposure radiation in this device is a light-emitting diode. A possibility of obtaining individual elements of the resistive mask (in particular, with the lateral size ~5 μm, height of ~70 μm, and aspect ratio of ~14) and also the titanium stamp microrelief (with the height up to ~40 μm) generated by means of reactive ion-beam etching through the resistive mask, is experimentally demonstrated.     

Design of microstereolithography system based on dynamic image projection for fabrication of three-dimensional microstructures

As demands for complex microstructures with high aspect ratios have increased, the existing methods, MEMS and LIGA, have had difficulties coping with the number of masks and fabricable heights. A microstereolithography technology can meet these demands because it has no need of masks and is capable of fabricating high aspect ratio microstructures. In this technology, 3D part is fabricated by stacking layers, 2D sections, which are sliced from STL file, and the Dynamic Image Projection process enables the resin surface to be cured by a dynamic image generated with DMD™ (Digital Micromirror Device) and one irradiation. In this paper, we address optical design process for implementing this microstereolithography system that takes the light path based on DMD operation and image-formation on the resin surface using an optical design program into consideration. To verify the performance of this implemented microstereolithography system, complex 3D microstructures with high aspect ratios were fabricated.     

使用平行束软X光透镜的深亚微米X射线光刻

使用本实验室研制的整体平行束软X光透镜作为准直器和电子枪软X光源相配,作成了平行束软X光源,用此平行束软X光源进行了深亚微米X射线光刻实验。刻出了1.0μm～0.2μm的线条。文中对实验装置和光刻结果作了简要的介绍。     

Synchrotron Radiation Lithography and MEMS Technique at NSRL

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聚合物基表面微结构的逐面式制造技术研究进展

聚合物基表面微结构在软体机器人、柔性电子器件、仿生机械、生物医学、组织工程等领域有着广泛的应用,将逐面式制造技术应用于聚合物基表面微结构的制造过程可解决传统微压印、光刻、逐点和逐线式制造方法加工周期长、效率低、大面积表面微结构制造脱模难等问题。发展聚合物基表面微结构的逐面式制造技术是当前先进制造技术的研究热点之一,具有广阔的应用前景。首先在阐述了常见的聚合物基表面微结构设计及其制造材料的基础上,重点论述了光刻、纳米压印、数字光投影式3D打印、能场辅助制造、自组装制造等五类逐面式成形制造技术方面的最新研究进展,包括各种制造技术的制造原理、工艺特点及表面微结构的典型应用等。最后,总结预测了聚合物基表面微结构设计、制造及应用方面的发展趋势,并对聚合物基表面微结构的逐面式成形制造技术的未来发展进行了展望。     

Microstructuring of optical surfaces: Technology and device for direct laser writing of diffractive structures

Results of development and testing of a scanning system of interference lithography are presented. The system is designed to form diffractive microstructures consisting of microgratings with a specified orientation, a size of 5–10 µm, and a period ranging from 0.6 to 1.5 µm. The total writing field of the system is 300 × 300 mm. The system is used to study direct laser writing of microgratings on chromium and amorphous silicon films applied by the method of magnetron sputtering onto the glass substrate surfaces. The device and technology of direct writing of microgratings can be further used to form antireflective subwave coatings of optical elements and graphical microstructured identification marks for product protection and also to manufacture diffractive attenuators of laser radiation.     

大高宽比、高线密度X射线透射光栅的制作

利用电子束光刻、X射线光刻和微电镀技术,成功制作了面积为1 mm × 1 mm,周期为300 nm,金吸收体厚度为1 μm的用于X射线显微成像技术的透射光栅。首先利用电子束光刻和微电镀技术在Si3N4薄膜上制作周期为300 nm,厚度为250 nm的高线密度光栅掩模。然后利用X射线光刻和微电镀技术复制厚度为1 μm,占空比接近1：1,高宽比为7的X射线透射光栅。整个工艺流程充分利用了电子束光刻技术制作高分辨率图形和X射线光刻技术制作大高宽比结构的优点     

High-resolution X-ray refraction imaging of rat lung and histological correlations

This study was performed to observe microstructures of the rat lung, using a synchrotron radiation beam and to compare findings with histological observations. X-ray refraction images from ex-vivo ventilating rat lung were obtained with an 8 KeV monochromatic beam and 20-mum thick CsI(Tl) scintillation crystal. The visual image was magnified using a 20x microscope objective and captured using an analog CCD camera. Obtained images were compared with conventional light microscopic findings from the same tissue. Pulmonary microstructures, including alveolar ducts, alveolar sacs, alveoli, alveolar walls, and perialveolar capillary networks were clearly identified with spatial resolution of as much as 1.2 mum and had good correlation with conventional light microscopic findings. The shape of alveoli appeared more round in SR images than in the light microscopic images. The results suggest that X-ray microscopy study of the lung using synchrotron radiation demonstrates the potential for clinically relevant microstructure of lung tissue without sectioning and fixation.     

Fabrication of hierarchical micro/nanostructures via scanning probe lithography and wet chemical etching

In this study, we propose a simple and effective method for fabricating hierarchical silicon structures via the combination of scanning probe lithography (SPL) and wet chemical etching. Here, silicon oxide structures were protruded from a 100-oriented silicon surface, followed by the passivation of silicon nitride by AFM tip-induced local oxidation. Based on the two-dimensional (2D) silicon oxide patterns, three-dimensional (3D) microstructures with high aspect ratios were formed by wet etching with HF and KOH. A variety of combinations of SPL and the etching process allowed us to fabricate diverse silicon-based structures such as deep-etched microstructures and multi-terraced nanostructures.     

Surface roughness and geometrical characterization of ultra-thick micro moulds for ceramic micro fabrication using soft lithography

Ceramic micro fabrication using soft lithography is a well-known technique used to pattern high-aspect-ratio microstructures. The quality of the pattern highly relies on the quality of the moulds. This paper describes the surface roughness and geometrical characterization of soft lithography technique for the fabrication of ceramic micro components. Effects of patterning materials and methods on the produced geometry, repeatability and surface roughness were studied and a comparative study was performed for the optimization process. UV lithography of BPR100 and SU-8 and deep reactive ion etching are the methods for fabricating the master mould. In addition, polydimethylsiloxane and Dragon Skin elastomeric have been used in the fabrication of the soft moulds. Mould geometry was inspected using SEM images while surface roughness was measured using stereo imaging. The results show that the maximum obtained thicknesses are 1,000, 250 and 500 μm for SU-8, BPR100 and DRIE moulds. In addition, their surface roughness values are higher than the SU-8. On the other hand, Dragon Skin shows demoulding problems despite it has smoother surface than PDMS mould.     

Effect of curing parameters and configuration on the efficacy of ultraviolet light curing self-adhesive masks used for abrasive jet micro-machining

Abrasive jet micro-machining (AJM) uses a high speed jet of particles to mechanically etch features such as micro-channels into a wide variety of target materials. Since the resulting air-particle jet is divergent, erosion resistant masks are required for patterning. Because of their ease of application, 50 and 100 μm thick commercially available ultraviolet (UV) light curing self-adhesive masks are potentially very useful in AJM. However, optimum curing parameters have until now been specified in terms of a curing time for a specific recommended curing unit, making extrapolation to other curing units impossible. Using masks to create straight 250–600 μm wide reference channels in borofloat glass, this paper quantified the optimum curing UV light energy density, and investigated the effect of differing UV exposure units (flat and cylindrical-backed), UV light energy densities, and mask configuration during curing, on the pattern transfer accuracy (before AJM), and the eroded micro-channel feature size. As expected, as long as the masks were cured at the same energy density, the pattern transfer accuracy did not depend on the curing unit. The most accurate pattern transfer to the mask film (widths within 5–7% of design) corresponded to energy densities between 516–774 and 387–516 mJ/cm² for the thick (100 μm) and thin (50 μm) masks, respectively. Under these conditions and for both exposure units, the average widths of the eroded channels after AJM were found to be within 3–9% of the intended design. Curing the masks outside this range resulted in eroded features that were approximately 15–20% and ∼5% larger than intended, for the thick and thin masks, respectively. The orientations of the channel patterns with respect to the curing cylinder axis did not affect the pattern transfer. However, when compared to the cylinder ends, curing at the midpoint along the cylinder length improved the pattern accuracy by approximately 3%, resulting in eroded features that were 10–20% closer to the design width. Finally, it was found that patterning multiple layers of masks improved the erosion resistance without compromising the feature width, enabling the AJM of higher aspect ratio features.     

X射线成像波带片及制作

研究了X射线成像波带片的工作原理和制作工艺。从理论上分析了波带片的空间分辨率与最外环宽度的关系,以及波带片衍射效率与厚度和折射率的关系。利用国家同步辐射实验室发展的加工工艺,即电子束光刻技术和X射线光刻技术结合制作波带片。实验结果表明:波带片最外环宽度为150 nm,高宽比为4,基本满足高分辨X射线成像波带片的高空间分辨率、大高宽比、高精度等要求。