用光致抗蚀剂作牺性层材料制作可动微机械

报道了用光致抗蚀剂作牺牲层材料制作可动微机械结构的一种新技术。用这种技术制作可动微机械,动件和固定件同时制作。同现有的牺牲层材料相比,光致抗蚀剂作牺牲层材料具有一些优越性。首先,光致抗蚀剂能直接涂敷,能直接光刻成形。此外,用光致抗蚀剂作牺牲层材料不影响结构的厚度和材料的选择。工艺优化后,结构洁净度、固定件与基片的结合强度及牺牲层去除速度都得到了改善。     

用于微镜制作的叠层光刻胶工艺及残余应力控制

对应用于微反射镜制作的叠层光刻胶牺牲层工艺及微反射镜表面残余应力控制进行了研究.讨论了光刻胶牺牲层在电镀时的污染问题,提出了用电镀结束后重新制作光刻胶牺牲层的方法来保证牺牲层表面质量.同时提出蒸发电镀相结合的工艺,解决了上层光刻胶溶剂穿过中间结构层浸入底层光刻胶的问题,并通过控制蒸发与电镀过程中应力状态不同的两层金属薄膜的厚度解决了微反射镜镜面存在残余应力问题.最后成功释放了620 μm×500 μm×2μm,悬空高12 μm的微反射镜结构.     

波导层不连续的Love波延迟线

Love波传感器的波导层和吸附层通常是不同材料的,一般先在整个器件表面覆盖一层声波导层材料,然后在感应区域对应的波导层上涂镀吸附层,但是这样会增大延迟线的插入损耗.文中设计了一种不连续波导层的Love波延迟线,即在感应区域,吸附层直接镀在压电基片上,同时兼作声波导层;在其他区域覆盖声波导层材料.实验器件制作在ST-90°X石英晶体上,中间感应区域用Au作波导层和吸附层,其他区域采用SU-8光刻胶作声波导层,结果表明,采用这种结构的延迟线可以降低损耗2 dB以上.     

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。     

一种表面可动微结构的释放新工艺

在表面微机械加工技术中,当牺牲层腐蚀后,已被释放的表面可动微结构会粘结在衬底上使器件失效。     

用于微反射镜制作的叠层光刻胶牺牲层工艺及残余应力控制

对应用于微反射镜制作的叠层光刻胶牺牲层工艺及微反射镜表面残余应力控制进行了研究。讨论了光刻胶牺牲层在电镀时的污染问题,提出电镀结束后重新制作光刻胶牺牲层的方法来保证牺牲层表面质量。同时提出蒸发-电镀相结合的工艺解决了上层光刻胶溶剂穿过中间结构层浸入底层光刻胶的问题,并通过控制蒸发与电镀过程中应力状态不同的两层金属薄膜的厚度解决了微反射镜镜面存在残余应力问题。最后成功释放了长620μm、宽500μm、厚2μm、悬空高为12μm的微反射镜结构。     

基于MEMS技术硅微悬臂梁制作工艺研究

针对非制冷红外热成像中的双材料硅微悬臂梁阵列的结构要求,在MEMS常见加工工艺的基础上,提出了单个硅微悬臂梁的制作工艺路线。工艺中使用高浓度HF溶液释放牺牲层磷硅玻璃（PSG）。探讨了双层材料氮化硅和铝之间的断裂及氮化硅和硅基底之间的粘连问题,对工艺中影响成品率的关键因素残余应力进行了分析。     

在表面张力和重力影响下回流微透镜的表面轮廓

介绍一种有限元方法，用它能计算软化光致抗蚀剂技术（回流技术）所成形折射微透镜的3-D表面轮廓。微透镜的几何形状可以是任意的。考虑了微透镜的表面张力和重力。重力对表面形状会有有利的影响，结果是能实现较小的焦点。微透镜参量给定时，用一种简单的比例规律，就能估算重力对轮廓形状的影响。将若干微透镜理论表面轮廓与用软化光致抗蚀剂技术所成形微透镜表面轮廓作了比较，它们的一致性良好。最后，证明这种方法对灵巧掩模折射微结构设计的实用性。     

蛇型步进式直线驱动器的研究

利用压电陶民电致伸缩性效应可以制成压电驱动器。用金属材料制成的一体化可动结构和叠层式压电元件可组成蛇型步进式直线驱动器,能实现高精度、高可靠性的直线步进驱动。分别地该直线驱动器的系统模型、控制方法及特点作了论述。     

高阻硅衬底上多孔硅牺牲层工艺的研究

采用离子注入的方法在高电阻率的硅衬底上选择性地形成低阻区,制备了多孔硅牺牲层,研究用"先做微结构后形成多孔硅"的多孔硅牺牲层工艺制作微悬空结构.     

New materials for rolling mechanisms

Technological progress makes more arduous the conditions under which many rolling mechanisms are required to operate and creates an ever increasing demand for improved materials of construction. Using a simple accelerated service-simulation test, new materials and recently developed surface treatments have been assessed under conditions of elevated temperature, high speed and unlubricated rolling contact. Methods of in situ lubrication by sacrificial cage materials have been explored. Lightweight and hollow rolling elements manufactured by electrodeposition have been developed. Modifications in steel manufacturing methods to avoid carbide segregation, and steels of reduced carbon content to limit deleterious carbide structural effects have been investigated. Some of the work of the National Engineering Laboratory (NEL) in this field is briefly reviewed.     

Structural design and testing of composite wing high-lift device

A problem for designing aviation structures made of sandwich-like polymer composite materials has been examined based on the example of a typical device for mechanizing a wing-spoiler. The spoiler’s loading pattern is chosen according to topological optimization. A way to determine the orientation, number, and proper order of layers laying has been examined as a problem of discrete optimization by using different algorithms. The peculiarities of layered structure simulation have been discussed. Tests results for spoiler have been presented and they verify the design and technological solutions.     

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.     

Interference photolithography with the use of resists on the basis of chalcogenide glassy semiconductors

The use of chalcogenide glassy semiconductors as an inorganic vacuum photoresist to obtain periodic relief structures on substrates of various compositions is investigated. It is shown that a chalcogenide resist can be successfully used in combination with interference lithography (including the immersion one) to form one- and two-dimensional submicron-size periodic structures with a spatial frequency of 300 to 8000 mm⁻¹. Technological processes of obtaining relief structures and lithographic masks with submicron sizes of elements on semiconductor, dielectric and metal substrates are developed, and their possible applications are described.     

Off-axis electron holography of patterned magnetic nanostructures

Magnetization reversal processes in lithographically patterned magnetic elements that have lateral dimensions of 70–500 nm, thicknesses of 3–30 nm and a wide range of shapes and layer sequences have been followed in situ using off-axis electron holography in the transmission electron microscope. This technique allows domain structures within individual elements and the magnetic interactions between them to be quantified at close to the nanometre scale. The behaviour of 30 nm-thick Co elements was compared with that of 10 nm-thick Ni and Co elements, as well as with Co/Au/Ni trilayers. The hysteresis loops of individual elements were determined directly from the measured holographic phase images. The reproducibility of an element's domain structure in successive cycles was found to be affected by the out-of-plane component of the applied magnetic field and by the exact details of its initial magnetic state. Close proximity to adjacent elements led to strong intercell coupling, and remanent states with the in-plane magnetic field removed included domain structures such as solenoidal (vortex) states that were never observed during hysteresis cycling. Narrow rectangular bars reversed without the formation of end domains, whereas closely separated magnetic layers within individual elements were observed to couple to each other during field reversal.     

Sensitivity of an optimized contour mask technique to errors in fabricating piecewise continuous relief diffractive optical elements

This paper considers the effect of errors in the technological process using an optimized contour mask technique for fabricating piecewise continuous relief diffractive optical elements on the reduction in the backward slopes of diffraction zones and the increase in the diffraction efficiency of the elements. The process parameter tolerances necessary for the implementation of the method are within the parameters of the standard microelectronic processes and equipment. The proposed method can be useful for laser writing systems and projection lithography that form the relief in a photoresist with a backward slope width exceeding 1 µm since it provides a significant improvement in the performance of the fabricated diffraction structures.     

Multiple fabrications of sacrificial layers to enhance the dimensional accuracy of microstructures in maskless projection microstereolithography

Microstereolithography (MSL) is a promising technology for producing fully three-dimensional microstructures with overhanging features and high-aspect ratios. In conventional stereolithography (SL), a layer thickness of ≈50–100 μm is obtained by using a recoater. However, a recoater cannot be used in MSL, where the layer thickness is typically ≈10 μm or less, since resin flow may break or distort the pre-fabricated layers. In most MSL systems, the resin surface (or layer thickness) is controlled by a free surface technique that employs resin gravity to refresh the resin surface over a given settling time. In addition, a sacrificial layer must be fabricated in MSL to create a flat initial surface and provide support, just as in SL. In this paper, the fabrication methodology and functionality of the sacrificial layer is investigated for microstereolithography microstructures fabricated using the free surface technique. Experimental data are presented that indicate the greater the number of sacrificial layers, the sharper the dimensional accuracy of the microstructures in the building direction. This is because multiple fabrications of the sacrificial layer affect the resin ‘wetting’ status on the substrate or pre-cured surfaces. Several microstructures were fabricated to verify the effect of multiple fabrications of the sacrificial layer on dimensional accuracy in the building direction.