金属微结构电铸制造用SU-8胶的热溶胀性研究

为解决金属微结构电铸制造用SU-8胶受热易溶胀的难题,在剖析热溶胀机理的基础上开展了实验研究,结合实验结果针对性提出尺寸补偿法、优化胶模结构和降低温度三项抑制热溶胀的措施。     

三维微小凹图式的加工及其与人神经母细胞瘤细胞的复合

采用紫外光光刻、硅蚀刻及软光刻技术分别制备了阴性光刻胶SU-8和聚乳酸及聚羟基乙酸共聚物(PLGA)微小凹图式.以人神经母细胞瘤细胞SH-SY5Y与三维微结构进行复合,采用扫描电子显微镜、光学显微镜及caicein荧光染色评价所加工图式的结构形态及细胞的生长行为.实验制备出名义直径约100/μm、高纵横比(接近或大于1)并可叠加微通道连接的SU-8及PLGA三维微小凹图式.所加工的图式透明,符合三维细胞生物传感器的光学检测的需要.细胞培养结果表明,该结构尺寸的图式能引导在三维环境神经细胞的排布、神经突起延伸及形态分化.     

基于二维金属亚波长孔阵列结构的MEMS红外辐射源特性研究

以MEMS红外气敏传感器为应用目标,采用MEMS技术设计和制作一种二维金属亚波长孔阵列结构红外辐射源。探讨了不同厚度SU-8膜对金属/电介质/金属(M/D/M)二维金属亚波长孔阵列结构在中远红外波段透射特性的影响。设计并制作了Au/SU-8/Au的M/D/M结构,测试采用傅里叶变换红外光谱仪器。同时对M/D/M结构不同电介质层情况下的中远红外波段透射特性进行了模拟。实验结果表明,SU-8厚度在小于1μm时,透射强度远大于厚度1μm以上的结构,且有透射强度最大值出现(SU-8厚度为360nm),同时,随着SU-8厚度的增加,透射谱峰值呈现规律性红移。     

阵列型微拓扑结构基底的制备及其对神经细胞电生物物理特性的影响

以紫外光光刻、硅蚀刻及软光刻技术制备了微柱阵列型细胞培养基底.实验发现,在4μm的结构高度下,当微柱特征尺寸大于或等于4 μm时,该法能制备结构规整清晰的聚二甲基硅氧烷微柱阵列型基底.特征尺寸为2μm的基底已经接近该法的极限加工能力,所加工的微柱阵列出现倒伏或缺失.采用一种简单的倾斜角法可以制备一种聚苯乙烯微球致密阵列...     

基于机器视觉辅助测量的精密电火花刻伤方法与系统

传统电火花刻伤机在工作时只对电机动作进行反馈,刀片损耗带来的误差通常靠人为增加进给量进行补偿,难以保证刻槽的形状与尺寸公差。为了更精确地获得刻伤过程中的刀片损耗量,提升闭环控制的电机精度,提出了一种基于机器视觉辅助测量刀片损耗的电火花刻伤方法,并依此设计了一套刻伤系统。实验中使用该系统计算出的刀片损耗量和实际测量值的误差在±5μm以内,同时得到的刻槽实际测量深度与系统计算的刻槽深度的误差在±10μm内。     

SU-8胶在深紫外光源下的光强分布模拟

本文根据菲涅尔衍射的原理,在考虑了折射、光刻胶对光的吸收以及硅片对光的反射的情况下,给出了SU-8胶在365 nm光源下经过方孔曝光时,光刻胶中光强的二维分布及三维分布的计算模拟.将试验结果与实际情况相比,表现出了一定的适用性,可以近似作为光刻胶形貌的最后近似.     

Research on wafer-lever vacuum package by glass frit at low temoerature

研究了玻璃浆料在低温下真空封装MEMS器件的工艺.封装过程中,采用了丝网印刷技术,丝网的线宽设计为100 μm,印刷后玻璃浆料线宽为160 μm左右,从而能够减小封装器件的尺寸,节省成本;另外,对玻璃浆料键合工艺做了研究,找到了较好的工艺条件,采用该工艺(预烧结温度425℃,键合温度430℃),得到的封装结构具有较高的封接强度(剪切力＞20 kgf)和良好的真空度,测得的漏率为10-9 cm3/s.     

条纹沟槽表面润湿性的试验研究

通过对铝基板及不锈钢基板上条纹沟槽表面接触角的测试,研究了条纹沟槽对材料表面润湿性的影响.试验用条纹沟槽表面采用准LIGA技术制备.该技术以波长为300～400 μm紫外光作为曝光光源,包括显影、表面活化、微电铸和去胶等工艺.接触角的测试采用DSA100接触角测试仪,选用液滴体积为5 μL.试验结果表明,条纹沟槽的存在...     

SU—8微小网孔阵列结构的形貌优化工艺研究

研究了曝光剂量对于小孔成型孔径的影响.实验中发现由于SU—8为负性光刻胶,曝光聚焦条件控制不佳会导致倾角较大的倒梯形结构,不利于液体喷射.为了实现陡直的图形结构,深入研究了衬底和紫外曝光焦平面的相对位置(散焦量),对于SU—8光刻胶图形边界倾角的影响机制.研究发现,当散焦量从-0.6μm变化到0.2μm时,SU—8光刻...     

(大连理工大学精密与特种加工教育部重点实验室，辽宁 大连，116024)

基于微注塑成型中熔体充模流动理论,对微尺度下熔体与壁面间的传热系数对熔体充模流动影响进行了研究.在分析两相间传热机理的基础上,讨论了宏观尺度流道和微观尺度流道中传热系数取值对熔体温度分布的影响.在引入传热系数模型的基础上,对正方形截面分别为500μm、300μm和200μm的三种长方形微流道中熔体充模流动进行三维数值模拟.通过与已有实验数据相比较,验证了模型的合理性,并分析了不同的模具温度和熔体温度下,采用常数传热系数和传热系数模型得到的熔体温度分布及其随微流道特征尺度变化规律.     

Electroplated compliant metal microactuators with small feature sizes using a removable SU-8 mould

In the work presented in this article a fabrication process for high aspect ratio metal microstructures has been developed using photoresist EPON SU-8. A smallest feature size of 2 μm with near vertical sidewalls has been achieved on a routine basis. The SU-8 photoresist has been used as mould for electroplating high aspect ratio metal micro actuators. A removal process has also been developed. The removal of the SU-8 mould after plating is done in a plasma asher using an oxygen or oxygen/fluorine plasma with plasma power as low as 200 W. To demonstrate the fabrication process a 10 μm thick nickel, electro-thermal micro actuator has been fabricated.     

Patterning of burnishing head for hard disk platters by synchrotron radiation lithography

This paper discusses the patterning of the burnishing head for hard disk platters on the AlTiC substrate, performed by X-ray exposure through X-ray mask to identify areas still left on the substrate after the photoresist development. The high energy and the low divergence of the synchrotron light provided the high-aspect-ratio microstructures with high accuracy patterns of burnishing head specifications. After the X-ray lithography was processed, the AlTiC substrate coated with the SU-8 hard mask was dry-etched with CF₄ of the RIE machine and run under the various conditions of the industrial process. An appropriate condition based on a total of 10 experimental conditions, which were based on the CCD technique, was investigated at Minitab using the data collected for analysis and compared with the standard specification. Based on the standard specification of the critical dimension of 8.02 µm and the etched depth of 30.0 µm, the best condition for the experiment, calculated by the desirability approach, was the 250 µm-thick SU-8 photoresist with an exposure dose of 23,010 mJ/cm³ and an RIE etching time of about 20 h. Mathematically, this condition offers a critical dimension and an etched depth of 7.02 and 30.11 µm, respectively. When the actual experiment was conducted to confirm the results, and we found that the critical dimension and the etched depth showed values of 7.03 and 30.02 µm, respectively.     

Fabrication of SU-8 photoresist micro–nanofluidic chips by thermal imprinting and thermal bonding

Micro–nanofluidic chips have been widely applied in biological and medical fields. In this paper, a simple and low-cost fabrication method for micro–nano fluidic chips is proposed. The nano-channels are fabricated by thermal nano-imprinting on an SU-8 photoresist layer followed by thermal bonding with a second SU-8 photoresist layer. The micro-channels are produced on the second layer by UV exposure and then thermal bonded by a third layer of SU-8 photoresist. The final micro–nano fluidic chip consists of micro-channels (width of 200.0 ± 0.1 μm and, depth of 8.0 ± 0.1 μm) connected by nano-channels (width of 533 ± 6 nm and, depth of 372 ± 6 nm), which has great potential in molecular filtering and detection.

     

Investigation in the interface adhesion strength between SU-8 photoresist and metal substrate by ultrasonic treatment

During the fabrication process of metal microstructures and microdevices by ultraviolet Lithographie Galvanoformung Abformung technology of SU-8, it is common for interface separation and bind failure due to the poor adhesion strength between SU-8 photoresist and metal substrate. In this paper, ultrasonic wave was introduced into the lithography process to improve the interface adhesion strength. Scratch test method was adopted to measure the interface adhesion strengths between SU-8 photoresist and metal substrate without ultrasonic treatment and with ultrasonic treatment under different ultrasonic conditions. The effects and corresponding mechanisms of ultrasonic time and ultrasonic power on the interface adhesion strength between SU-8 photoresist and metal substrate were investigated. The results showed that due to the input of the ultrasonic vibration, the crosslink network characteristics of SU-8 photoresist were changed. The internal stress in SU-8 photoresist was reduced and the interface adhesion strength was improved. The interface adhesion strength firstly increased and then decreased with the increase of ultrasonic time. The maximum interface adhesion work was 0.427 J/m² at an optimized ultrasonic time of 10 min, which was higher than that of the sample without ultrasonic treatment by 39.5 %. Besides, in the experimental conditions, the interface adhesion strength first increased and then decreased with the increase of the ultrasonic power and the maximum interface adhesion strength attained at the ultrasonic power of 352 W. The ultrasonic treatment method can effectively improve the interface adhesion strength, so as to increase the product yield and performance.     

High aspect ratio micromolds for the electroplating of micro electro discharge machining tools

A new approach using micro systems technology for the fabrication of micro electro discharge machining tool electrodes using a combination of positive and negative photoresist fabricated with near UV-lithography as high aspect ratio micromolds was developed. Micromolds with heights varying from 200 to 650 μm and an aspect ratio of up to 26:1 were fabricated using SU-8?, a negative photoresist, as a micromold for the electrodeposition of the micro tool electrodes. Besides serving as a micromold, SU-8? is also used as an insulator to protect the sidewalls of the tool electrodes from corrosions. The fabrication of the SU-8? micromold was optimized to avoid cracks and delaminations. In the experiments, electrodes made of Cu, WCu, and CoFe were deposited into these High Aspect Ratio Micro Structure Technology (HARMST) micromolds. Furthermore, the process technique for electroplating in deep micromolds is discussed in this paper.     

Fabrication of polymer micro-tip by optical lensing technique

Fabrication of polymer micro-tips using SU-8 negative photoresist for bio-applications is reported. The SU-8 processing technology and isotropic glass etching process have been developed and utilized to fabricate micro-tips on glass substrate by applying optical lensing effect during photolithography. Experimentally, micro-tips of 25?μm base diameter, ~1?μm tip diameter, and ~250?μm height, have been demonstrated.     

Modelling and simulation of forming process of the lithographically fabricated out-of-plane microlens using a cellular automata method

Three dimensional (3D) cellular automata (CA) model has been successfully applied in photoresist etching simulation in recent years. In this paper, a simplified 3D CA model is used to simulate the etching process of out-of-plane microlens fabricated on thick SU-8 photoresist. The simulation results are compared with experimental results. This CA model can be developed as a computer-aided design tool to predict the optimum process parameters during the forming of lithographically fabricated microlens.     

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

 This paper reports a novel way to compensate the air gap between photomask and photoresist for eliminating UV light diffraction on photoresist, which greatly increases the sidewall straightness of high-aspect-ratio resist structures. In this research, SU-8 negative tone photoresist was used for experiments, and glycerol was employed as an index match material for bridging air gap between photomask and photoresist during exposure. Results showed that a high aspect ratio wall structure of 156 μm thick and 25 μm wide had a 45% pattern width error when exposed under 100 μm air gap, while glycerol compensated process accomplished a straight resist wall without appreciable error. This method is simple and cheap to employ, compared to the usage of costly thick-photoresist-film spinner for resist planarization. Numerical simulation on the diffraction effect upon the structure wall has also been conducted. The calculated and experiment wall profiles showed similarity in trend. Received: 10 August 2001/Accepted: 24 September 2001     

Fabrication of CNT-carbon composite microstructures using Si micromolding and pyrolysis

A fabrication method of carbon nanotube (CNT)-carbon composite microstructures has been developed. CNT-carbon composite microstructures with dimensions from 10 micrometers to several hundred micrometers have been fabricated by pyrolysis process from the patterned SU-8 photoresist mixed with 1 wt% of CNTs at temperature of ~600 °C under inert atmosphere. The resulting composite microstructures with a high aspect ratio of ~34 can be successfully fabricated by this novel fabrication method. This research provides a simple approach that is compatible with microfabrication technology and is capable of fabricating composite microstructures with reproducible shape and dimensions, at desired locations. This approach has potential for the further exploring of applications of composite micro/nano structures as functional units in various microdevices. Also the ultramicroindentation hardness of the CNT-carbon composite films was investigated by nanoindentation measurement.     

Reduction of diffraction effect for fabrication of very high aspect ratio microchannels in SU-8 over large area by soft cushion technology

Edge bead due to spin coating has been found to cause an air gap as large as 53 m for a 99-m thick (measured at the wafer center) SU-8 coating over a 4-in. wafer. This caused poor mask width replication and non-uniformity of SU-8 pattern width. We have devised a process using a soft cushion technology to improve mask dimension replication and large-area pattern uniformity. A soft cushion was placed beneath the substrate to produce convex bending of the wafer in order to improve the contact between the mask and photoresist top surface during UV exposure. Dramatic improvements in pattern uniformity, from over 30% variation in SU-8 width across the wafer to less than 10%, and mask width replication, from 54% deviation from mask width to 20%, have been demonstrated. Numerically calculated increases in SU-8 width from the wafer center to the edge bead using the Fresnel diffraction equation match well with observed values. Further, employment of this technique with a narrow (10 m) dark-field mask enabled the fabrication over the entire surface of 4-in. diameter wafers of dense SU-8 gratings separated by microchannels with aspect ratio over 18.