Imprinted polymer stamps for UV-NIL

Thermal step and stamp nanoimprint lithography (SSIL) offers an alternative to fabricate transparent polymer stamps for UV-imprinting. The fabrication process does not require any other subsequent steps, e.g. dry etching or anti adhesive coating.In this work, we have manufactured UV-stamp by combining patterns of two different silicon masters. The patterns of the silicon masters were transferred into resin coated quartz plate by sequential imprinting. The first master consisted gratings with 50 nm features and the second master consisted dot arrays of 350 nm diameter features. The novel idea is the ability to create a large UV-stamp using a combination of small masters. Thus fabricated UV-stamps were used for demonstrating step and repeat UV-imprinting. The quality of the UV-stamps and imprints were analyzed by AFM. High fidelity patterns were achieved in respect to patterns in the original silicon master.     

Investigation of the separation of 3D-structures with undercuts

The separation of masters with 3D undercut structures from thin spin-coated layers of PDMS (Sylgard 184) on Si was investigated. In order to identify typical failure types and to figure out potential limitations imposed by the material, masters with different undercut widths were prepared. Imprint was chosen as the replication technique, where only thin base layers remain on the substrate below the 3D undercut structures. Two typical failure types were observed during separation, neck failure and base layer failure. It was found that surface quality of the master is a major impact factor. Small defects in the surface of the PDMS induced by the master result in large area tear-off of the undercut replica during separation. Defect-free masters could be successfully imprinted and separated with base layer thicknesses down to about 1 μm for undercut widths of up to 8 μm.     

沉积在聚合物表面上的金属薄膜自发形成图案的实验研究

用离子溅射法在聚二甲基硅氧（polydimethylsiloxane,PDMS）表面沉积的金膜因金属与聚合物之间热膨胀系数的差异从而导致了具有正弦界面、微米尺度的波长和振幅的复杂而有序的褶皱图案。用光刘技术在硅片制备图形结构作为模板,通过复制模铸得到表面具有浮雕结构的聚二甲基硅氧烷基片。改变浮雕结构可以调控其上沉积的金膜的褶皱图案呈规则有序的排列。这种多尺度的复合结构将光刘技术、复制模铸和物理自组装等有效结合,可广泛应用于微纳制造领域。     

Fabrication of antireflection nanostructures by hybrid nano-patterning lithography

Antireflection (AR) nanostructures are fabricated on a glass substrate using hybrid nano-patterning lithography (H-NPL) consisting of nanosphere lithography (NSL) and UV-nanoimprint lithography (UV-NIL). The shape and diameter of the AR nanostructures were controlled by fabricating Si masters with different RIE conditions. The shapes of the AR nanostructures were a pillar-type and a corn-type. The diameters of the AR nanostructures were about 350 and 250 nm, respectively. AR nanostructures were successfully nanoimprinted on glass in accordance with Si master prepared by NSL. The pillar-type AR nanostructure with diameter of 350 nm exhibited the transmittance of over 98% in the wavelength range from 1100 to 2200 nm. From the results, the fabricated AR nanostructures demonstrate the possibility to improve the efficiency of optoelectronic devices such as a photo-detector and an IR-LED.     

Poly vinyl alcohol re-usable masters for microneedle replication

We present the first results of microstructure replica with re-usable masters in poly vinyl alcohol (PVA). Microneedles of heights ranging from 500 to 1100 μm were fabricated through double-exposure deep X-ray lithography (DXRL) process and successfully replicated. A single PVA master was used as a template to successfully replicate up to 10 PMMA microneedle arrays, suggesting that this method might be a possible alternative to PDMS processes. A preliminary characterization of the relationship between the surface roughness of the substrates and the force required for demoulding was also performed.     

Fabrication of high aspect ratio nanostructures on 3D surfaces

A combination of different materials and processes was used to create high aspect ratio nanostructures on 3D surfaces. The high aspect ratio structures were formed on thermoplastic foils using UV-Nanoimprintlithography (UV-NIL) with a poly (dimethylsiloxane) (PDMS) stamp which was fabricated by soft lithography. An epoxy mixture with a higher glass transition temperature than the thermoplastic foil was used as a resist for UV-NIL. The hydrophobicity of structured substrates was characterized by the surface contact angle. Substrates with an additional chemical treatment were also produced and characterized. Results of contact angle measurement showed that superhydrophobic surface properties can be obtained with structured and chemically treated samples. The foils were further used as a substrate in a thermoforming process to transfer the structures into a microchannel. Using this process, 3D structured foils can be fabricated with high accuracy. The foils were used as a master structure for a replica molding process which allowed the fabrication of 3D structured polymer parts. With the presented method, microchannels with superhydrophobic surface properties can be fabricated.     

非梯度折射率型面阵平面微透镜

采用常规的光刻热熔法及灰度掩模技术,结合离子束蚀刻与溅射制作面阵非梯度折射率型平面折射和平面衍射微透镜,定性分析了不同的工艺条件下所得到的平面端面微光学折种和形貌特征。给出了在石英衬底表面通过光刻热熔工艺和氩离子束蚀刻所得到的两种球面及圆弧轮廓特征的面阵册形掩模的表面探针测试曲线,对平面微透镜阵列与IRCCD成像芯片和半导体激光器阵列的集成结构作了初步分析。     

Full wafer microlens replication by UV imprint lithography

The fabrication of microlenses is of great interest for several applications in the field of optics like wafer level cameras, homogenization of light, and coupling of light into glass fibers. Especially for low-cost optical products, microlenses have to be fabricated with a high throughput at an adequate quality. One way to fulfil these requirements is the patterning of microlenses by UV imprint lithography (UV-IL). Within this work, microlenses were replicated into the UV curing material PAK-01 by step and stamp UV-IL on silicon substrates with a diameter of 150 mm. The resulting substrates were used as masters to cast PDMS templates. These PDMS templates can be used for high throughput full wafer UV-IL. Additionally, quartz substrates with a diameter of 100 mm were patterned which could be directly used as so called “optowafers”. Master and patterned microlenses were inspected by scanning electron microscopy and with a white light profilometer. The results clearly demonstrate the excellent quality of the replication process and the capability of UV-IL to pattern microlenses on full wafer level for high throughput applications.     

Fabrication of ordered micro- and nano-scale patterns based on optical discs and nanoimprint

A simple method to fabricate one-dimensional(1-D) and two-dimensional(2-D) ordered micro- and nano-scale patterns is developed based on the original masters from optical discs, using nanoimprint technology and soft stamps. Polydimethylsiloxane(PDMS) was used to replicate the negative image of the 1-D grating pattern on the masters of CD-R, DVD-R and BD-R optical discs, respectively, and then the 1-D pattern on one of the PDMS stamps was transferred to a blank polycarbonate(PC) substrate by nanoimprint. The 2-D ordered patterns were fabricated by the second imprinting using another PDMS stamp. Different 2-D periodic patterns were obtained depending on the PDMS stamps and the angle between the two times of imprints. This method may provide a way for the fabrication of complex 2-D patterns using simple 1-D masters.     

Direct imprint of Al foil for metallization of high-aspect ratio Al lines in nano/micro patterned SiO2/Si

Patterning techniques of Al micro/nano-structures become more and more critical as optical components and microelectronic devices continue to be scaled down. In this work, we fabricated gap-filled Al lines in SiO₂/Si masters by using the direct thermal imprint of molten Al. As a result, gap-filled Al lines with width ranging from 0.25 to 20 μm and depth ranging from 6 to 127 μm could be achieved without any further processing step such as CVD and PVD. The process studied here has shown the possibility to extend trench filling capability to 0.25 μm structures with 24:1 aspect ratio, which are difficult to be obtained by other conventional Al metallization methods.     

Fabrication of Ordered Nanostructured Arrays Using Poly(dimethylsiloxane) Replica Molds Based on Three‐Dimensional Colloidal Crystals

Hexagonally arrayed structures of colloidal crystals with uniform surface are a good candidate for master molds to be used in soft lithography. Here, the fabrication of periodically arrayed nanostructures using poly(dimethylsiloxane) (PDMS) molds based on three‐dimensionally (3D) ordered colloidal crystals is reported. A robust, high‐quality 3D colloidal‐crystal master molds is prepared using the colloidal suspension containing a water‐soluble polymer. The surface patterns of the 3D colloidal crystals can then be transferred onto a polymer film via soft lithography, by means of the replication of the surface pattern with PDMS. Various hexagonally arrayed nanostructure patterns can be fabricated, including close‐packed and non‐close‐packed 2D arrays and honeycomb structures by the structural modification of the 3D colloidal‐crystal templates. The replicated hexagonally arrayed structures can also be used as templates for producing colloidal crystals with 2D superlattices.     

Reinforcement of a PDMS master using an oxide-coated silicon plate

In this work, a new method was developed to increase the stiffness of Polydimethylsiloxane (PDMS) masters using oxide-coated silicon plates, aimed at reducing the residual and deflecting deformations of the PDMS masters for proper pattern transfer. Using this method, these two types of deformations in the reinforced PDMS master have been reduced.     

2维光子晶体抗反膜的制作及其特性分析

为了研究2维亚波长光栅的抗反射特性,分析了2维光子晶体的2维光栅结构,通过全息束光干涉的方法,在光刻胶上制作了六角结构的2维全息光子晶体结构.把具有2维全息光子晶体结构的光刻胶作为母版采用全息模压的方法,将结构复制到薄膜材料上.结果表明,这种抗反膜在红外波段具有增透作用,与理论分析相吻合.     

Tapered conical polymer microneedles fabricated using an integrated lens technique for transdermal drug delivery

Administration of protein and DNA biotherapeutics is limited by the need for hypodermic injection. Use of micron-scale needles to deliver drugs in a minimally invasive manner provides an attractive alternative, but application of this approach is limited by the need for suitable microneedle designs and fabrication methods. To address this need, this paper presents a conical polymer microneedle design that is fabricated using a novel integrated lens technique and analyzed for its ability to insert into the skin without mechanical failure. Microneedle master structures were fabricated using microlenses etched into a glass substrate that focused light through SU-8 negative epoxy resist to produce sharply tapered structures. Microneedle replicates were fabricated out of biodegradable polymers by micromolding. Because microneedle mechanical properties are critical to their insertion into the skin, we theoretically modeled two failure modes (axial mode and transverse mode), and analytical models were compared with measured data showing general agreement. Guided by this analysis, polymer microneedles were designed and demonstrated to insert to different depths into porcine skin in vitro. "Long" polymer microneedles were also demonstrated in human subjects to insert deeply without failure.     

Fabrication of large-core 1/spl times/16 optical power splitters in polymers using hot-embossing process

Large-core (42 /spl times/43 /spl mu/m) 1/spl times/16 optical power splitters in polymers have been fabricated. Y-branch waveguide structures with and without offsets in the arc-bending regions were designed by the beam propagation method software and molded by a silicon-mold master using a hot-embossing process. The optical power splitters were produced by epoxy core filling and ultraviolet curing processes. The average insertion losses at a wavelength of 850 nm were measured to be 19.8 dB with offset and 17.1 dB without offset, respectively. The maximum uniformities were 3.3 dB with offset and 3.9 dB without offset, respectively.     

一种基于谐振原理的微型压力传感器设计

设计了一种结构简单的微型石英谐振式压力传感器,该传感器芯片由力学转换元件、谐振敏感元件和支撑元件3部分构成。仿真分析了压力100kPa内传感器输出频率与输入压力的关系,经线性拟合后得出其最大相对非线性误差为0.09%。采用石英深槽湿法腐蚀的方法加工出了芯片3个元件结构,并经镀膜及键合等后工序制作出了传感器芯片,其性能实测值与仿真结果基本吻合,验证了结构及工艺方案的可行性。     

硅油稀释PDMS法制备紫外纳米压印软模板

软模板的制作是紫外纳米压印中关键的技术,模版的分辨率直接决定了压印图形的最小分辨率。使用具有高度均匀、100nm级孔洞阵列结构的多孔氧化铝作为母版,使用基于液态浇铸的硅油稀释聚二甲基硅氧烷(硅油和聚二甲基硅氧烷的质量比为1:2)法制备出具有规则点阵结构的软模板。通过SEM和AFM表征发现,特征图形得到了有效转移,特征尺度保持在100nm左右。相对于传统的模板制备方法,此方法成本低、流程简单、适合大规模生产,是一种非常有前途的软模板制备方法。     

利用非化学汽相沉积法制备掺Yb^3＋光子晶体光纤的研究

提出了一种制备掺Yb^3＋光子晶体光纤（PCF）的新方法,即：非化学气相沉积法。利用溶液掺杂法,将SiO2、YiCl3、AlCl3、K2CO3材料在水溶液中混合,再蒸发、烘干得到均匀的混合材料,经2 000℃以上高温熔炼制备出高掺Yb^3＋浓度石英玻璃。用掺Yb^3＋石英玻璃作为纤芯,通过堆积法制备光纤预制棒,再经拉丝...     

激光能量对脉冲激光沉积法制备ZnO薄膜性能的影响

脉冲激光沉积技术(PLD)易于获得高质量的氧化物薄膜已成为一种重要的制备ZnO薄膜的技术.采用脉冲激光沉积(PLD)(KrF准分子激光器:波长248 nm,频率5 Hz,脉冲宽度20 ns)方法在氧气气氛中以高纯Zn(99.999%)为靶材、在单晶硅和石英衬底表而成功生长了ZnO薄膜.通过X射线衍射仪、表面轮廓仪、荧光光谱仪、紫外可见分光光度计对合成薄膜材料的晶体结构、厚度、光学性质等进行了研究,分析了激光能量变化对其性能的影响.实验结果表明我们使用PLD法可以制备出(002)结晶取向和透过率高于75%的ZnO薄膜,激光能量为450 mJ的ZnO薄膜的发射性能较好,但激光能量的增加不能改善薄膜的透光率.     

基于石英的声表面波宽量程气压传感器研究

该文提出了一种面向航天航空飞行器宽量程压力检测的声表面波(SAW)传感器的设计方法。在犢切石英晶体上,利用半导体平面工艺设计并制作了单端对谐振型传感器,在此基础上,通过石英干法刻蚀工艺制备了压力参考腔,并构建了全石英封装的面压式传感结构。利用搭建的气压测试平台,对制备的SAW 传感器性能进行测试,测试结果表明,传感器在0~3．6 MPa量程内获得了1．36kHz/MPa的检测灵敏度,并表现出良好的线性度。